本申请是2006年1月27日提交的发明名称为“用于地层的水力压裂的方法”的第200680051820.7号发明专利申请的分案申请。This application is a divisional application of the No. 200680051820.7 invention patent application filed on January 27, 2006, with the title of "Method for Hydraulic Fracturing of Formation".
技术领域technical field
本发明涉及地层中的水力压裂，更特别地，涉及用于优化裂缝传导性的方法。The present invention relates to hydraulic fracturing in formations, and more particularly, to methods for optimizing fracture conductivity.
背景技术Background technique
碳氢化合物（石油、天然气等）通过钻探穿过含碳氢化合物地层的井从地层中获得。这为碳氢化合物到达地面提供了部分流路。为使碳氢化合物“产出”，即从地层行进到井眼并最终行进至地面，必须具有足够畅通的流路。Hydrocarbons (oil, natural gas, etc.) are obtained from formations by drilling wells through hydrocarbon-bearing formations. This provides a partial flow path for hydrocarbons to reach the surface. In order for hydrocarbons to "come out," that is, to travel from the formation to the wellbore and eventually to the surface, there must be adequate flow paths.
水力压裂是通过设置从井眼至储层的高传导性裂缝或使高传导性裂缝从井眼延伸至储层中提高井的产量的主要措施。在第一阶段期间，水力压裂流体通过井眼以高的速率和高的压力注入地层。压裂流体注入速率超过地层的渗入速率，从而在砂面（sandface）产生增大的水压。当压力超过临界值时，地层或岩石破裂和产生裂缝。该地层裂缝比地层孔隙更有渗透性。Hydraulic fracturing is the main measure to increase the production of wells by setting or extending high-conductivity fractures from the wellbore to the reservoir. During the first stage, hydraulic fracturing fluid is injected through the wellbore into the formation at a high rate and pressure. The rate of fracturing fluid injection exceeds the rate of infiltration of the formation, creating increased water pressure at the sandface. When the pressure exceeds a critical value, the formation or rock ruptures and creates fractures. The formation fractures are more permeable than formation pores.
在下一个阶段期间，支撑剂沉积在裂缝中，以防止裂缝在注入停止后闭合。最终形成的被支撑的裂缝能够使可恢复的流体即油、气或水的流动得以改善。砂、砂砾、玻璃珠、胡桃壳、陶瓷颗粒、烧结矾土以及其他物质可用作支撑剂。During the next stage, proppants are deposited in the fractures to prevent the fractures from closing after injection has stopped. The resulting propped fractures enable improved flow of recoverable fluids, ie oil, gas or water. Sand, gravel, glass beads, walnut shells, ceramic particles, sintered alumina, and other substances can be used as proppants.
水力压裂流体是含有增稠剂例如可溶解多糖的水溶液，以便提供足够的粘性来传输支撑剂。典型的增稠剂是聚合物，例如胍尔胶（phytogeneous polysaccharide，植物多糖）和胍尔胶衍生物（羟丙基胍尔胶，羧甲基羟丙基胍尔胶）。其他聚合物也可用作增稠剂。具有胍尔胶的水表现出具有与聚合物浓度成比例的粘度的线性凝胶。在聚合物链之间提供结合的交联剂用于形成足够强的偶联来增加凝胶粘性和产生粘弹性。用于胍尔胶的常用的交联剂包括硼、钛、锆和铝。Hydraulic fracturing fluids are aqueous solutions containing thickeners, such as soluble polysaccharides, in order to provide sufficient viscosity to transport proppants. Typical thickeners are polymers such as guar (phytogeneous polysaccharide) and guar derivatives (hydroxypropyl guar, carboxymethylhydroxypropyl guar). Other polymers can also be used as thickeners. Water with guar exhibits a linear gel with a viscosity proportional to the polymer concentration. Cross-linkers provide bonds between polymer chains for forming couplings strong enough to increase gel viscosity and create viscoelastic properties. Commonly used crosslinking agents for guar gum include boron, titanium, zirconium and aluminum.
支撑剂保持剂通常用于水力压裂处理的较后阶段期间，以限制放入地层中的支撑剂发生倒流。例如，支撑剂可涂覆有在井底条件下被激活的可固化树脂。不同材料例如纤维束、或纤维状材料或可变形材料也已用于保持裂缝中的支撑剂。可推测，纤维在支撑剂中形成三维网络，从而对其加强并限制其倒流。Proppant retaining agents are typically used during later stages of a hydraulic fracturing treatment to limit backflow of proppant placed in the formation. For example, proppants may be coated with curable resins that are activated under downhole conditions. Different materials such as fiber bundles, or fibrous or deformable materials have also been used to hold proppants in fractures. Presumably, the fibers form a three-dimensional network in the proppant, thereby strengthening it and limiting its backflow.
水力压裂处理的成功取决于水压裂缝传导率和裂缝长度。裂缝传导率是支撑剂渗透率与裂缝宽度的乘积；单位通常表示为毫达西-英尺。裂缝传导率受多个已知参数影响。支撑剂颗粒尺寸的分布是影响裂缝渗透性的一个关键参数。裂缝面之间的支撑剂浓度为另一关键参数（以每平方英尺裂缝面的支撑剂的磅数表示）并影响裂缝宽度。可考虑采用高强度的支撑剂、具有优良的支撑剂传输特性的流体（本身使裂缝内的重力沉降最小化的能力）、高支撑剂浓度、或者大的支撑剂作为手段来提高裂缝传导性。弱的材料、差的支撑剂传输和窄的裂缝都会导致井的低产量。相对价廉的低强度材料例如砂用于具有较小内应力的地层的水力压裂。较高成本的材料例如陶瓷、矾土等用于具有较高内应力的地层中。产生的流体和支撑剂之间的相互化学作用可显著改变支撑剂的特性。从而，由于油井和气井通常运转多年，因此应当考虑支撑剂的长期的抗压碎能力。The success of hydraulic fracturing treatments depends on hydraulic fracture conductivity and fracture length. Fracture conductivity is the product of proppant permeability and fracture width; units are usually expressed in millidarcy-feet. Fracture conductivity is affected by several known parameters. The distribution of proppant particle size is a key parameter affecting fracture permeability. Proppant concentration between fracture faces is another critical parameter (expressed in pounds of proppant per square foot of fracture face) and affects fracture width. High strength proppants, fluids with excellent proppant transport properties (inherently capable of minimizing gravitational settling within the fracture), high proppant concentrations, or large proppants may be considered as means to increase fracture conductivity. Weak material, poor proppant transport and narrow fractures can all lead to low production from the well. Relatively inexpensive low strength materials such as sand are used for hydraulic fracturing of formations with low internal stress. Higher cost materials such as ceramics, alumina, etc. are used in formations with higher internal stress. The resulting chemical interaction between the fluid and the proppant can significantly alter the properties of the proppant. Thus, since oil and gas wells typically operate for many years, the long-term crush resistance of the proppant should be considered.
支撑剂充填层必须生成比周围地层岩石具有更高水力传导率的层。裂缝内的支撑剂充填层可作为可渗透多孔结构建模，地层流体通过该层的流动通常通过众所周知的Darcy定律（1）或Forchheimer公式（2）描述：The proppant pack must generate a layer with higher hydraulic conductivity than the surrounding formation rock. A proppant pack within a fracture can be modeled as a permeable porous structure, and the flow of formation fluids through this formation is usually described by the well-known Darcy's law (1) or the Forchheimer equation (2):
其中in
P为裂缝中流体压力；P is the fluid pressure in the fracture;
x为从井眼沿裂缝的距离；x is the distance from the wellbore along the fracture;
μ为地层流体的粘度；μ is the viscosity of formation fluid;
u为地层流体的流动（渗入）速度；u is the flow (seepage) velocity of formation fluid;
k为支撑剂充填层的渗透率；k is the permeability of the proppant pack;
β为描述Darcy渗入定律的非线性修正的称作β因子的系数；β is a coefficient called the β-factor describing the non-linear modification of Darcy's law of penetration;
ρ为地层流体的密度。ρ is the density of formation fluid.
裂缝渗透率乘以裂缝宽度的结果称为“水力传导率”。裂缝设计最重要的方面是对特殊地层条件进行水力传导率优化。裂缝设计理论和方法在多篇科技文章和专著中有充分描述。Reservoir Stimulation，3rd，Economides,Michael J.和Nolte，Kenneth G.，JohnWiley and Sons（1999）是提供良好裂缝设计方法的参考文献的好的实例。The result of multiplying the fracture permeability by the fracture width is called "hydraulic conductivity". The most important aspect of fracture design is hydraulic conductivity optimization for specific formation conditions. Fracture design theory and methods are well described in several scientific articles and monographs.Reservoir Stimulation ,3rd , Economides, Michael J. and Nolte, Kenneth G., John Wiley and Sons (1999) are good examples of references that provide good fracture design methods.
裂缝优化过程应在支撑剂强度、水力裂缝传导率、支撑剂分布、材料成本和在特定储层中进行水力压裂处理的成本之间实现均衡。大的支撑剂的情况阐释了在优化过程中所作的折衷。使用大直径支撑剂时，水力裂缝传导率的显著增加是可能的。然而，在给定的地层内应力下，当受到较高裂缝闭合应力时，大直径支撑剂会在更大程度上被压碎，导致支撑剂充填层的有效水力传导率下降。此外，支撑剂颗粒越大，它们更多地在注入点附近的裂缝中跨接和卡住。The fracture optimization process should strike a balance between proppant strength, hydraulic fracture conductivity, proppant distribution, material cost, and cost of hydraulic fracturing treatments in a particular reservoir. The case of large proppants illustrates the trade-offs made in the optimization process. Significant increases in hydraulic fracture conductivity are possible when using large diameter proppants. However, under a given formation internal stress, large-diameter proppants will be crushed to a greater extent when subjected to higher fracture closure stress, resulting in a decrease in the effective hydraulic conductivity of the proppant-packed formation. In addition, the larger the proppant particles, the more they bridge and get stuck in fractures near the point of injection.
根据支撑剂的耐压碎的能力选择特殊的支撑剂，所述支撑剂在经受裂缝闭合应力时提供足够的裂缝传导率；且它能够低成本地深深地流入水力裂缝。根据水力压裂过程使用的体积和质量，支撑剂位列水之后的第二位。与砂相比，陶瓷支撑剂具有更佳的β因子以及更高的强度。然而，陶瓷支撑剂的成本高出砂的成本的许多倍。因此，对于利用支撑剂的水力压裂来说，裂缝传导性的改善需要巨大的成本，通常达到传统水力压裂处理的总成本的20至60％。A particular proppant is selected based on its ability to resist crushing; the proppant provides sufficient fracture conductivity when subjected to fracture closure stress; and it is able to flow deeply into hydraulic fractures at low cost. Proppants come second after water in terms of the volume and mass used in the hydraulic fracturing process. Ceramic proppants have a better beta factor and higher strength than sand. However, the cost of ceramic proppants is many times that of sand. Therefore, for hydraulic fracturing with proppants, fracture conductivity improvement entails enormous costs, typically reaching 20 to 60% of the total cost of conventional hydraulic fracturing treatments.
除了上述因素以外，尚有其它支撑剂特性使得碳氢化合物的生产变得复杂。首先，地层流体通常绕过用于处理的大部分流体。（残留在支撑剂层中的流体破坏裂缝的传导性。）现场研究表明，天然气井中水力压裂流体从裂缝中的恢复量平均仅为处理过程中所注入流体的20％至50％或者更少。地层流体可能仅沿支撑剂充填层内的成“手指”的形式的多个通道流动，或在裂缝清洁处理过程中仅通过支撑剂充填层靠近井眼的一部分。包含残余的粘性凝胶的裂缝部分阻止流体流动，从而降低有效的水力裂缝传导性。在处理后降低压裂流体粘性是增加压裂流体从支撑剂充填层孔隙的恢复的有效方式。添加称为“破胶剂（breaker）”的物质促进凝胶粘度的降低。破胶剂具有多种作用机制，但最通常的情况是它们通过裂解聚合物链以减小它们的长度并由此降低聚合物溶液的粘度起作用的。不同的破胶剂的特征在于，诸如破胶剂与聚合物之间的反应速率、所述特定破胶剂的激活或激活解除温度的参数。更好的裂缝清洁可通过使用高的破胶剂浓度实现，但过高的破胶剂浓度可导致凝胶粘度过早降低，这可能损害处理设计并引起处理的过早完成，即被遮挡。延迟作用的破胶剂例如封装方法被开发用于解决该问题。封装的破胶剂是活性破胶剂化学制品例如氧化剂粒体，其涂覆有将氧化剂与聚合物隔离并延迟它们的反应的保护壳体。通过包括在裂缝闭合处的机械应力的作用在内的多种机制使壳体破坏并释放破胶剂。封装的破胶剂能够使得在水力压裂流体中使用较高的破胶剂浓度，因此可提高裂缝清洁的程度。In addition to the above factors, there are other proppant properties that complicate hydrocarbon production. First, formation fluids typically bypass most fluids used for treatment. (The fluid trapped in the proppant layer destroys the conductivity of the fracture.) Field studies have shown that recovery of hydraulic fracturing fluid from fractures in natural gas wells averages 20 to 50 percent or less of the fluid injected during treatment . Formation fluids may flow only along multiple channels in the form of "fingers" within the proppant pack, or only through a portion of the proppant pack close to the wellbore during a fracture cleaning treatment. Fracture portions containing residual viscous gel impede fluid flow, thereby reducing effective hydraulic fracture conductivity. Reducing the viscosity of the fracturing fluid after treatment is an effective way to increase the recovery of the fracturing fluid from the pores of the proppant pack. Addition of substances known as "breakers" facilitates the reduction of the viscosity of the gel. Breakers have a variety of mechanisms of action, but most commonly they work by cleaving polymer chains to reduce their length and thereby reduce the viscosity of the polymer solution. Different breakers are characterized by parameters such as the rate of reaction between the breaker and the polymer, the activation or deactivation temperature of that particular breaker. Better fracture cleaning can be achieved by using high breaker concentrations, but too high a breaker concentration can lead to premature reduction in gel viscosity, which can compromise the treatment design and cause premature completion of the treatment, ie, shadowing. Delayed action breakers such as encapsulation methods were developed to address this issue. Encapsulated breakers are active breaker chemicals, such as oxidizer granules, coated with a protective shell that isolates the oxidizer from the polymer and delays their reaction. The shell is broken and the breaker is released by a variety of mechanisms including the action of mechanical stress at the crack closure. Encapsulated breakers enable the use of higher breaker concentrations in hydraulic fracturing fluids, thereby increasing fracture cleaning.
降低裂缝传导率的另一因素为支撑剂充填层中的孔隙堵塞，所述堵塞源于压裂过程中形成的地层颗粒、支撑剂压碎形成的支撑剂颗粒以及不能混溶的流体（The Impact ofNon-Darcy Flow on Production from Hydraulically Fractured Gas Wells，SPEProduction and Operations Symposium，3月24-27日，Oklahoma City，Oklahoma，2001；AStudy of Two-Phase，Non-Darcy Gas Flow Through Proppant Pacs，SPE Production&Facilities，第15卷第4期，2000年11月）。因此，显然，其中地层流体流经通过生成的通道网络而不通过支撑剂充填层中的小孔隙的裂缝可通过以下多种机制增加裂缝的水力传导率：降低惯性损失、提高压裂流体的清除、减小产生显著的两相流压力损失的毛细作用力、以及通过捕获地层翅片和压碎的支撑剂碎片消除孔隙喉道封堵。Another factor that reduces fracture conductivity is pore plugging in the proppant pack from formation particles formed during fracturing, proppant particles from proppant crushing, and immiscible fluids (The Impact ofNon-Darcy Flow on Production from Hydraulically Fractured Gas Wells, SPE Production and Operations Symposium, March 24-27, Oklahoma City, Oklahoma, 2001; AStudy of Two-Phase, Non-Darcy Gas Flow Through Proppant Pacs, SPE Production&Facilities, No. 15, No. 4, November 2000). Thus, it is clear that fractures in which formation fluids flow through the resulting channel network rather than through the small pores in the proppant pack can increase the hydraulic conductivity of the fracture through several mechanisms: reduced inertial losses, enhanced fracturing fluid scavenging , reducing capillary forces that create significant two-phase flow pressure losses, and eliminating pore throat plugging by trapping formation fins and crushed proppant fragments.
近年来，在北美许多低渗透性地层中的压裂处理通过利用不含支撑剂或仅含有少量支撑剂的低粘度水力压裂流体进行泵送。该方法具有多个名称，其中最常用的是“水压裂（waterfrac）”。水压裂处理所产生的裂缝实际上不含支撑剂。可以预计，在裂缝产生和传播期间，所产生的裂缝面相对彼此偏移。所导致的不规则表面特征（凸凹不平）的错位防止两个裂缝面在闭合时形成紧密密封。据报道加入少量支撑剂会增强不规则和错位的裂缝面的作用。然而，由于传输性较差，支撑剂趋向于积聚在套管射孔的下方，最有可能沿所产生的水力裂缝的基部积聚。由于沿窄的水力裂缝支撑剂在压裂流体中的沉降率较高、以及由于支撑剂传输能力不足（均因为压裂流体的低粘性），因此会发生所述积聚。当水压裂终止而使压裂流体注入停止时，裂缝长度和高度立即缩减。这将略微压紧支撑剂，所述支撑剂在接近井眼的裂缝基部处保持为“沙丘状”。因为沙丘的有限长度、宽度以及强度通常有限（通常采用低强度砂），水压裂通常特征在于产生短的、低传导率的裂缝（Experimental Study ofHydraulic Fracture Conductivity Demonstrates the Benefits of Using Proppants，SPE Rocky Mountain Regional/Low-Permeability Reservoirs Symposium andExhibition，3月12-15日，丹佛，科罗拉多州，2000）。In recent years, fracture treatments in many low-permeability formations in North America have been pumped with low-viscosity hydraulic fracturing fluids that contain no proppant or only a small amount of proppant. The method has several names, the most common of which is "waterfrac". Fractures created by hydraulic fracturing treatments are virtually proppant-free. It is expected that during fracture initiation and propagation, the generated fracture faces are offset relative to each other. The resulting misalignment of irregular surface features (asperities) prevents the two fracture faces from forming a tight seal when closed. The addition of small amounts of proppant has been reported to enhance the action of irregular and misplaced fracture faces. However, due to poor transport, proppant tends to accumulate below the casing perforation, most likely along the base of the resulting hydraulic fracture. The accumulation occurs due to the high settling rate of the proppant in the fracturing fluid along narrow hydraulic fractures, and due to insufficient proppant transport capacity (both due to the low viscosity of the fracturing fluid). When the hydraulic fracturing is terminated so that the injection of the fracturing fluid is stopped, the fracture length and height decrease immediately. This will slightly compact the proppant, which remains "dune-like" near the base of the fracture in the wellbore. Because of the finite length, width, and often limited strength of sand dunes (often with low-strength sands), hydraulic fracturing is often characterized by the creation of short, low-conductivity fractures (Experimental Study of Hydraulic Fracture Conductivity Demonstrates the Benefits of Using Proppants, SPE Rocky Mountain Regional/Low-Permeability Reservoirs Symposium and Exhibition, March 12-15, Denver, Colorado, 2000).
上述表明，水压裂由地层流体流过窄的通道的网络产生，所述窄的通道网络由于表面岩石缺陷引起的未完全闭合而在裂缝内产生，即水压裂处理产生低传导性裂缝。提高水力压裂传导性的一种方法是在裂缝中构造支撑剂团块，这与构造连续的支撑剂充填层不同。美国专利6776235公开了一种用于地层水力压裂的方法，包括：初始阶段，所述初始阶段将水力压裂流体注入井眼，所述水力压裂流体包含增稠剂以在地层中产生裂缝；以及交替阶段，所述交替阶段将包含支撑剂的水力压裂流体周期性地引入井眼中，以形成防止裂缝闭合的柱状体形式的支撑剂团块，所述包含支撑剂的水力压裂流体的区别在于它们传输支撑剂的能力不同，因此差异在于支撑剂沉降率。该方法交替采用载有支撑剂的压裂流体的阶段与不含支撑剂的压裂流体的阶段。在每一阶段支撑剂在裂缝中的沉积量可通过改变流体传输特性（例如粘性和弹性）、支撑剂密度、直径、浓度和压裂流体注入速率被调节。The above shows that water fracturing results from the flow of formation fluids through a network of narrow channels created within fractures due to incomplete closure caused by surface rock imperfections, ie the water fracturing process creates low conductivity fractures. One way to improve hydraulic fracture conductivity is to build proppant clusters in the fracture, as opposed to building a continuous proppant pack. US Patent 6776235 discloses a method for hydraulic fracturing of a formation comprising an initial stage of injecting a hydraulic fracturing fluid into the wellbore, the hydraulic fracturing fluid containing a thickening agent to create fractures in the formation and alternating stages of periodically introducing proppant-containing hydraulic fracturing fluid into the wellbore to form proppant clusters in the form of columns that prevent fracture closure, the proppant-containing hydraulic fracturing fluid The difference lies in their ability to transport proppant and thus the difference in proppant settling rate. The method alternates stages of proppant-laden fracturing fluid with stages of proppant-free fracturing fluid. The amount of proppant deposited in the fracture at each stage can be adjusted by varying fluid transport properties (eg, viscosity and elasticity), proppant density, diameter, concentration, and fracturing fluid injection rate.
本专利的方法提供了在裂缝中产生支撑剂团块或岛状体、以及在支撑剂团块或岛状体之间产生供地层流体流动的通道。然而，本方法采用的支撑剂的周期注入涉及支撑剂的每一部分首先沿井传输；然后，通过管柱的穿孔进入裂缝；以及进一步沿着裂缝的长度通过裂缝。由于含有支撑剂和不含支撑剂的压裂流体具有不同的比重，因此含有支撑剂的流体可沉降或位于所述不含支撑剂的流体之下。这种沉降导致裂缝中的支撑剂团块的非均匀分布。The method of this patent provides for the creation of proppant clusters or islands in fractures and the creation of channels between the proppant clusters or islands for formation fluid flow. However, the periodic injection of proppant employed by the present method involves transporting each portion of the proppant first down the well; then, through the perforation of the tubing string into the fracture; and further along the length of the fracture through the fracture. Due to the different specific gravity of proppant-containing and proppant-free fracturing fluids, the proppant-containing fluid may settle or lie beneath the proppant-free fluid. This settling results in a non-uniform distribution of proppant clusters in the fracture.
发明内容Contents of the invention
术语“支撑剂”通常用于指在水力压裂处理期间混入压裂流体并被泵送进入井眼的粒状材料。该支撑剂形成地层流体可渗透的多孔层（bed）、阻止地层闭合并在处理完成后保持裂缝面分离。在传统处理中，技术人员可从在给定地层的闭合应力下以最佳费用提供所需的渗透性（水力传导率）的多种类型的粒状材料中选择。普通支撑剂为高级的精选石英砂；铝矽酸盐陶瓷、烧结矾土以及硅酸盐陶瓷珠；以及涂覆有不同的有机树脂的多种类型的材料。由胡桃壳、玻璃珠和有机成分制成的支撑剂也可被泵送。支撑剂选择的最重要的因素之一是单个粒体的尺寸分布。在所有其它条件相同时，与具有相同的平均颗粒尺寸但具有宽的支撑剂分布的等效支撑剂相比，裂缝中具有窄的尺寸分布的支撑剂具有更高的渗透性。The term "proppant" is commonly used to refer to the granular material that is mixed into the fracturing fluid and pumped into the wellbore during hydraulic fracturing treatments. The proppant forms a porous bed that is permeable to formation fluids, prevents formation closure and keeps fracture faces separated after treatment is complete. In conventional processing, the technician can select from a variety of types of granular material that provide the desired permeability (hydraulic conductivity) at optimal cost given the closure stress of the formation. Common proppants are high-grade select quartz sand; aluminosilicate ceramics, sintered alumina, and silicate ceramic beads; and various types of materials coated with different organic resins. Proppants made from walnut shells, glass beads and organic components can also be pumped. One of the most important factors in proppant selection is the size distribution of individual grains. All other things being equal, a proppant with a narrow size distribution in a fracture has a higher permeability than an equivalent proppant with the same average particle size but a broad proppant distribution.
关于支撑剂的选择和使用的这些标准惯例不适用于此处所述的本发明。在本专利申请中，术语“支撑剂和/或支撑材料”被定义为“添加至压裂流体中以在裂缝内产生坚固和稳定结构的任何固体材料、粒体、纤维或其它材料”。同样，所有通常公认的传统支撑剂仍被认为是本发明可使用的支撑剂。然而，其它材料例如宽范围内分选的砂、金属带和针、盘、研磨粒体、有机和无机纤维也被认为是本发明所涉及到的支撑剂和/或支撑材料。These standard practices regarding the selection and use of proppants do not apply to the invention described herein. In this patent application, the term "proppant and/or propping material" is defined as "any solid material, particulate, fiber or other material added to a fracturing fluid to create a strong and stable structure within a fracture". Likewise, all generally accepted conventional proppants are still considered usable proppants in the present invention. However, other materials such as widely sorted sand, metal belts and needles, disks, abrasive grains, organic and inorganic fibers are also considered proppants and/or support materials with respect to the present invention.
术语“纤维”通常用于以下本发明的描述和权利要求中。为了本发明的目的，术语“纤维”是指这样的任何材料或实际物体，其中，在三维空间中的任一维度与其它两个维度中的任一维度或两个维度的长度之比超过5：l。这意指物体的长宽比大于5：1。因此，通常所认识的纤维为本发明所涉及到的纤维。同样，通常所指的带或板按定义也为本发明所涉及到的纤维。The term "fiber" is used generally in the following description and claims of the invention. For the purposes of the present invention, the term "fiber" means any material or physical object in which, in three-dimensional space, the ratio of the length of any one dimension to either or both of the other two dimensions exceeds 5 :l. This means that the aspect ratio of the object is greater than 5:1. Therefore, generally recognized fibers are the fibers involved in the present invention. Likewise, what is generally referred to as tape or sheet is also by definition the fiber involved in the present invention.
本发明提供了一种用于地层的水力压裂的经济有效方法，使得裂缝对于地层流体来说具有高的水力传导率。本发明产生在大部分裂缝面区域上分布的坚固的支撑剂团块或岛状体，在处理完成后它们可防止裂缝壁闭合。在这些岛状体与团块之间形成并由这种团块保持敞开的所述通道和敞开区域包含足够大的供地层流体流动的截面。The present invention provides a cost-effective method for hydraulic fracturing of formations such that the fractures have high hydraulic conductivity to formation fluids. The present invention produces strong proppant clusters or islands distributed over most of the fracture face area, which prevent fracture wall closure after treatment is complete. The channels and open areas formed between these islands and the mass and held open by such mass comprise a cross-section large enough for the flow of formation fluids.
通常，水力压裂处理以顺序的两个或多个阶段活动依次执行。在多数压裂处理的通常被称作“充填”的第一阶段，水基或油基流体以足够高的压力和速率被泵送至地层中，以形成水力压裂。在该阶段过程中，流体常通过使用各种稠化剂被粘化；本领域技术人员可控制粘度以影响裂缝的最终几何结构。此处所述本发明采用这种充填阶段。Typically, hydraulic fracturing treatments are performed sequentially in two or more stages of sequential activity. In the first stage of most fracturing treatments, commonly referred to as "packing," water- or oil-based fluids are pumped into the formation at a pressure and velocity high enough to create a hydraulic fracture. During this stage, the fluid is often viscosified through the use of various thickeners; those skilled in the art can control the viscosity to affect the final geometry of the fracture. The invention described here employs this filling phase.
在充填阶段之后即刻并通常连续地进行通常被称为“支撑阶段”的压裂的主阶段。在传统处理中，该阶段通常涉及泵送含有恒定或浓度增大的传统支撑剂的流体。这在处理终止时产生多孔材料层。本领域技术人员知道如何针对给定地层条件选择适用的支撑剂，以使裂缝的水力传导率最大。在传统处理中，“支撑阶段”时通常执行泵送直至处理完成。通常“支撑阶段”的末尾被称为“尾随”阶段。在“尾随”阶段中涂覆有树脂的支撑剂和/或纤维被加入，作为控制支撑剂在处理后回流的措施。Immediately and usually continuously following the pack stage, the main stage of fracturing, often referred to as the "propping stage", occurs. In traditional processing, this stage typically involves pumping a fluid containing a constant or increasing concentration of traditional proppants. This produces a layer of porous material at the end of the process. Those skilled in the art know how to select an appropriate proppant for a given formation condition to maximize the hydraulic conductivity of the fracture. In traditional processing, pumping is usually performed during the "propping phase" until processing is complete. Often the end of the "support phase" is called the "trailing" phase. Resin-coated proppants and/or fibers are added during the "tail" stage as a measure to control proppant flowback after treatment.
相比，在本发明中，支撑阶段包括一系列的交替子阶段，其中一些所述交替子阶段涉及支撑材料，下文称之为“支撑子阶段”；一些所述交替子阶段涉及载送流体，下文称之为“载送子阶段”。包含支撑材料的至少一个子阶段和不包含支撑材料的子阶段向至裂缝执行泵送。支撑子阶段的尺寸和组成的方式使得支撑材料聚集形成防止裂缝闭合的高强度的柱状体和岛状体、以及在团块之间形成供地层流体流动的通道。由于裂缝的水力传导性是通过敞开通道形成的，因此本发明的一部分允许支撑材料成分可选择成在给定储层条件下使所得的岛状体的压缩强度和抗腐蚀性最优化。所得团块或岛状体的渗透性或者无关紧要，或者为次要的。In contrast, in the present invention, the support phase comprises a series of alternating sub-phases, some of which involve support material, hereinafter referred to as "support sub-phases"; some of which involve carrier fluid, Hereinafter referred to as the "carrier sub-phase". At least one substage containing support material and a substage not containing support material perform pumping into the fracture. The propped sub-stages are sized and composed in such a way that the propped material aggregates to form high strength pillars and islands that prevent fracture closure and forms channels between the agglomerates for formation fluid flow. Since the hydraulic conductivity of the fracture is formed through the open channels, part of the present invention allows the proppant material composition to be selected to optimize the compressive strength and corrosion resistance of the resulting islands for a given reservoir condition. The permeability of the resulting clumps or islands is either insignificant or of minor importance.
本发明的另一个方面是包含支撑材料的子阶段可包含增大此前支撑剂团块的附加的加强和加固材料。加强和加固意指这样的任何化学和/或物理处理，即，用于促进颗粒材料粘合在一起；或用于增加将颗粒保持在一起的摩擦力；或当被一些外部作用力作用时机械地限制颗粒分离。加强处理的特定实例可为纤维（长宽比大于5：1的颗粒）、可变形材料以及颗粒表面上的可导致这些颗粒相互紧密粘结的树脂涂层。Another aspect of the invention is that the sub-stage comprising proppant material may comprise additional strengthening and strengthening material that augments the former proppant mass. Reinforcing and reinforcing means any chemical and/or physical treatment, i.e., used to promote the adhesion of particulate material together; or to increase the frictional force holding particles together; or to mechanically limit particle separation. Specific examples of strengthening treatments are fibers (particles with an aspect ratio greater than 5:1), deformable materials, and resin coatings on the surface of particles that cause these particles to adhere tightly to each other.
在许多情况下，当支撑剂被引入压裂流体中时可有利地引入加强材料，尽管该加强材料可被连续地引入到流体中。In many cases, it may be advantageous to introduce the reinforcing material when the proppant is introduced into the fracturing fluid, although the reinforcing material may be continuously introduced into the fluid.
加强材料可为有机、无机、或者有机和无机纤维。这些纤维也可被处理或制造，以仅包括粘合涂层，或包括涂覆有当通过裂缝时溶于压裂流体中的非粘性物质层的粘合涂层。加强材料也可为：具有球状或细长形状的金属颗粒；有机或无机物质的板；直径上为被成形为盘状的陶瓷、金属或金属合金；或在长度和宽度上被成形为矩形的陶瓷、金属或金属合金，对于所有这些材料，三个维度中的任意两个维度之间的比例大于5：1。Reinforcing materials can be organic, inorganic, or both organic and inorganic fibers. These fibers may also be treated or fabricated to include only a bond coat, or a bond coat coated with a layer of a non-stick substance that dissolves in the fracturing fluid as it passes through the fracture. The reinforcing material can also be: metallic particles having a spherical or elongated shape; plates of organic or inorganic substances; ceramics, metals, or metal alloys shaped as disks in diameter; or rectangular shaped in length and width Ceramics, metals or metal alloys, for all these materials the ratio between any two of the three dimensions is greater than 5:1.
优选地，第二阶段还涉及将试剂导入压裂流体中来增加压裂流体的支撑剂悬浮能力。该试剂可为具有长度远大于直径的细长颗粒的材料。Preferably, the second stage also involves introducing reagents into the fracturing fluid to increase the proppant suspending capacity of the fracturing fluid. The agent may be a material having elongated particles whose length is much greater than the diameter.
细长颗粒可与支撑剂同时、或单独地即间歇性连续地被导入压裂流体中。The elongated particles may be introduced into the fracturing fluid simultaneously with the proppant, or separately, ie intermittently and continuously.
优选地，细长颗粒长度大于2mm，直径为3至200μm。Preferably, the elongated particles have a length greater than 2 mm and a diameter of 3 to 200 μm.
支撑剂颗粒可仅具有粘合涂层，或具有涂覆有在通过裂缝时溶于压裂流体中的非粘合物质层的粘合涂层。The proppant particles may have a bond coat only, or a bond coat coated with a layer of a non-bond substance that dissolves in the fracturing fluid as it passes through the fracture.
在一些地层条件下，当采用上述方法时，可有利地执行涉及将支撑剂连续地引入压裂流体中的压裂处理的最终尾随阶段，且支撑剂在该阶段具有大致均匀的颗粒尺寸。同时，可在压裂流体中引入加强材料和/或具有可增强压裂流体的支撑剂悬浮能力的细长颗粒的材料。Under some formation conditions, when employing the methods described above, it may be advantageous to perform the final tail-off stage of the fracturing treatment involving continuous introduction of proppant into the fracturing fluid, with the proppant having a substantially uniform particle size at this stage. At the same time, reinforcing materials and/or materials with elongated particles that may enhance the proppant suspending ability of the fracturing fluid may be introduced into the fracturing fluid.
第二实施例second embodiment
另一方法可通过构造用于地层的水力压裂的分布的支撑剂柱状体形成高的传导性裂缝。该第二实施例涉及第一阶段（充填阶段），在所述第一阶段，含有增稠剂的压裂流体被注入井眼中；以及第二阶段，在所述第二阶段，支撑剂被连续地添加到注入的压裂流体中（并因此进入所产生的裂缝中），以防止裂缝闭合。在本发明中，第二阶段还涉及将试剂周期性地引入压裂流体中，以促进在所产生的裂缝中形成支撑剂团块。地层流体流过的敞开通道分隔开支撑剂。Another approach may be to form highly conductive fractures by constructing distributed proppant columns for hydraulic fracturing of the formation. This second embodiment involves a first stage (pack stage) in which fracturing fluid containing thickener is injected into the wellbore; and a second stage in which proppant is continuously are added to the injected fracturing fluid (and thus into the created fracture) to prevent fracture closure. In the present invention, the second stage also involves the periodic introduction of agents into the fracturing fluid to promote the formation of proppant clusters in the resulting fractures. Open channels through which formation fluids flow separate the proppants.
为形成支撑剂团块，在基于从试剂导入压裂流体中的时刻经过多少时间的特定时间间隔后，试剂与压裂流体发生反应。该时间间隔在处理过程中被监测并被改变，以在所产生的裂缝的不同位置处触发试剂与压裂流体之间的反应。由该反应形成的团块也将在整个裂缝分布。所述反应延迟通过多种不同的机制中的一种机制实现，所述多种机制包括但不仅限于以下机制：改变试剂的化学成分；将试剂封装在溶于压裂流体中的壳体内；与其它试剂颗粒和裂缝面碰撞而腐蚀壳体；当闭合时在裂缝壁之间压碎壳体；将试剂封装于在压裂流体中膨胀并破裂的半渗透性壳体中；将试剂封装在允许试剂缓慢扩散到压裂流体中的半膜或多孔壳体中；以及将试剂封装在能够溶解或冲洗掉的壳体中。To form a proppant cluster, the reagent reacts with the fracturing fluid after a certain time interval based on how much time has elapsed since the time the reagent was introduced into the fracturing fluid. This time interval is monitored and varied during the treatment to trigger a reaction between the reagent and the fracturing fluid at different locations of the created fracture. The clumps formed by this reaction will also be distributed throughout the fracture. The reaction delay is achieved by one of a number of different mechanisms including, but not limited to, the following: changing the chemical composition of the reagent; encapsulating the reagent in a shell that is dissolved in the fracturing fluid; and Other reagent particles collide with the fracture face to corrode the shell; crush the shell between the fracture walls when closed; encapsulate the reagent in a semi-permeable shell that swells and ruptures in the fracturing fluid; The slow diffusion of the agent into the semi-membrane or porous shell in the fracturing fluid; and the encapsulation of the agent in the shell which can be dissolved or flushed away.
该试剂可为使得压裂流体粘度剧烈、显著局部降低的添加剂，此后刚处理的流体中携带的支撑剂将在裂缝面之间沉降或卡塞。The agent may be an additive that causes a drastic, significant localized reduction in the viscosity of the fracturing fluid, after which the proppant entrained in the freshly treated fluid will settle or jam between the fracture faces.
添加剂可为在裂缝内受控释放剂时反应的压裂流体破胶剂。压裂流体破胶剂可为氧化剂、酶、（交联剂的）螯合剂或者可将流体pH值改变到使得交联剂或聚合物主链不稳定的程度的化学试剂。任一情况下所得结果均为与压裂流体反应且导致压裂流体粘度的显著降低的破胶剂。催化剂可被引入压裂流体中，以在需要时增加破胶剂与压裂流体的反应速率。The additive may be a fracturing fluid breaker that reacts upon controlled release of the agent within the fracture. Fracturing fluid breakers may be oxidizing agents, enzymes, chelating agents (of the cross-linker), or chemical agents that may alter the pH of the fluid to such an extent that the cross-linker or polymer backbone is destabilized. The result in either case is a breaker that reacts with the fracturing fluid and results in a significant reduction in the viscosity of the fracturing fluid. Catalysts may be introduced into the fracturing fluid to increase the rate of reaction of the breaker with the fracturing fluid if desired.
添加剂也可以是破坏压裂流体交联剂的类型的，例如但不仅限于螯合剂、用于锆酸盐交联剂的EDTA和NTA、以及用于硼酸盐交联剂的山梨糖醇和聚乙烯醇。这些添加剂可用具有不同厚度或具有在裂缝的不同位置处释放添加剂的释放机制的壳体加以封装。也可使用封装或延迟释放的酸和/或碱（base）。Additives can also be of the type that break down frac fluid crosslinkers such as but not limited to chelating agents, EDTA and NTA for zirconate crosslinkers, and sorbitol and polyethylene for borate crosslinkers alcohol. These additives can be encapsulated with shells of different thicknesses or with release mechanisms that release the additives at different locations in the fracture. Encapsulated or delayed release acids and/or bases may also be used.
在裂缝中启动支撑剂团块形成的试剂可以是降低支撑剂颗粒活动性的添加剂。实例为涂覆有一种材料的纤维束，所述材料在压裂流体中溶解使得纤维水合和散布并增加它们的浓度。这些添加剂也可为当被加热到某一温度时恢复它们的原始形状的材料，例如缠绕成球形而在被加热时可伸直或增加它们的体积的纤维。The agent that initiates the formation of proppant clusters in the fracture may be an additive that reduces the mobility of the proppant particles. An example is a fiber bundle coated with a material that dissolves in the fracturing fluid to hydrate and spread the fibers and increase their concentration. These additives may also be materials that return to their original shape when heated to a certain temperature, such as fibers wound into spherical shapes that straighten or increase their volume when heated.
添加剂可为具有高吸收能力的材料。具有高吸收能力的颗粒可涂覆有在通过裂缝过程中或在压裂流体温度升高过程中或这些情况的组合时溶解的壳体。Additives may be materials with high absorption capacity. Particles with high absorptive capacity may be coated with a shell that dissolves during passage through the fracture or during an increase in the temperature of the fracturing fluid, or a combination of these.
添加剂可为在地层温度下表面变为粘性的粒体、纤维或板。这些元件可具有粘合表面并涂覆有溶于压裂流体中的非粘合物质层。Additives may be granules, fibers or plates whose surface becomes sticky at formation temperatures. These elements may have an adhesive surface and be coated with a layer of a non-adhesive substance dissolved in the fracturing fluid.
第三实施例third embodiment
根据另一本发明实施例，一种用于地层的水力压裂的方法涉及：第一阶段（充填），在所述第一阶段，含有增稠剂的压裂流体被注入井眼中；第二阶段，在所述第二阶段，支撑剂连续地被引入注入的压裂流体中和所产生的裂缝中，以防止其闭合。此外，所述方法包括第三阶段，在所述第三阶段，将低粘度流体注入压裂流体中。所述流体由于其粘度与压裂流体粘度之间的差异作为将支撑剂分为离散团块的侵入物渗入到压裂流体中，并形成供地层流体流过的通道。According to another embodiment of the invention, a method for hydraulic fracturing of a formation involves: a first stage (packing) in which a fracturing fluid containing a thickening agent is injected into the wellbore; a second In the second stage, proppant is continuously introduced into the injected fracturing fluid and into the created fracture to prevent its closure. Additionally, the method includes a third stage in which a low viscosity fluid is injected into the fracturing fluid. The fluid penetrates into the fracturing fluid as an intrusion breaking the proppant into discrete masses due to the difference between its viscosity and the fracturing fluid viscosity, and forms channels through which the formation fluid flows.
与第一实施例中所述方法相似，第二和第三实施例中的第二阶段可包括引入具有细长颗粒的材料和/或加强材料、以及使用具有这些同样特性的支撑剂。同时，在附加的最后阶段可涉及将具有大致均匀颗粒尺寸的支撑剂、和加强材料和/或具有细长颗粒的材料连续地引入压裂流体中。Similar to the method described in the first embodiment, the second stage in the second and third embodiments may include introducing materials with elongated particles and/or reinforcing materials, and using proppants with these same characteristics. Simultaneously, an additional final stage may involve the continuous introduction of proppant having a substantially uniform particle size, and reinforcing material and/or material having elongated particles into the fracturing fluid.
附图说明Description of drawings
以下附图伴随着本发明的描述：The following drawings accompany the description of the invention:
图1显示相对于支撑剂浓度的压裂流体粘度。Figure 1 shows fracturing fluid viscosity versus proppant concentration.
图2显示在本发明的方法的实施过程中形成在裂缝中的支撑剂团块。Figure 2 shows proppant clusters formed in fractures during the practice of the method of the present invention.
图3显示在根据第二实施例的方法的实施过程中形成在裂缝中的支撑剂团块。Figure 3 shows proppant clusters formed in fractures during the performance of the method according to the second embodiment.
图4显示在根据第三实施例的方法的实施过程（从a）至d）进行）中形成在裂缝中的支撑剂团块，其中，在用稀薄流体替换粘稠流体时形成了粘性指状体。图中所示为数值模拟的结果。显示为灰色的是具有支撑剂的粘稠流体。显示为黑色的是穿入支撑剂充填层并在充填层中产生敞开通道的稀薄流体。若较粘稠的流体具有屈服应力，则可加强所形成的通道的稳定性。Figure 4 shows a proppant cluster formed in a fracture during the implementation of the method according to the third embodiment (proceeding from a) to d) in which viscous fingers are formed when viscous fluid is replaced by thinner fluid body. The figure shows the results of the numerical simulation. Shown in gray is viscous fluid with proppant. Shown in black is the thin fluid that penetrates the proppant pack and creates open channels in the pack. If the more viscous fluid has a yield stress, the stability of the channel formed can be enhanced.
具体实施方式detailed description
在用于地层的水力压裂方法的本发明的第一实施例中，此处和下文称为“充填阶段”的第一阶段涉及以可在砂面处产生水力压裂的足够高的流速将压裂流体注入井眼。所述充填阶段时执行泵送，直至裂缝尺度足以容纳随后在支撑剂阶段泵送的泥浆。所述充填的体积可根据本领域已知的裂缝设计方法设计（Reservoir Stimulation，3rd Ed.，M.J.Economides，K.G.Nolte，Editors，John Wiley and Sons，New York，2000）。In a first embodiment of the invention for a method of hydraulic fracturing of a formation, the first stage, referred to herein and hereinafter as the "packing stage", involves pumping Fracturing fluid is injected into the wellbore. Pumping is performed during the pack phase until the fracture size is sufficient to accommodate the mud that is then pumped in the proppant phase. The filled volume can be designed according to fracture design methods known in the art (Reservoir Stimulation,3rd Ed., MJ Economides, KGNolte, Editors, John Wiley and Sons, New York, 2000).
水基压裂流体通常添加有用于增加流体粘性的天然或合成水溶性聚合物，并在充填以及随后的支撑阶段中始终使用。这些聚合物包括但不限于：胍尔胶；包括甘露糖与半乳糖的高分子量多糖；或胍尔胶衍生物，例如羟丙基胍尔胶、羧甲基胍尔胶、羧甲基羟丙基胍尔胶。基于硼、钛、锆或铝化合物的交联剂通常用于增加聚合物的有效分子量，从而使其更适用于高温井。Water-based fracturing fluids are often fortified with natural or synthetic water-soluble polymers to increase fluid viscosity and are used throughout the pack and subsequent propping phases. These polymers include, but are not limited to: guar gum; high molecular weight polysaccharides including mannose and galactose; or guar gum derivatives such as hydroxypropyl guar, carboxymethyl guar, carboxymethylhydroxypropyl Guar gum. Crosslinkers based on boron, titanium, zirconium or aluminum compounds are often used to increase the effective molecular weight of the polymer, making it more suitable for use in high temperature wells.
在小的程度上，纤维素衍生物例如羟乙基纤维素、羟丙基纤维素和羧甲基羟乙基纤维素与交联剂一起使用或不与交联剂一起使用。黄原胶与与硬葡聚糖这两个生物聚合物被证明具有良好支撑剂悬浮能力，但是与胍尔胶衍生物相比更为昂贵，因此较少使用。聚丙烯酰胺与聚丙烯酸脂聚合物以及共聚物通常用于高温应用场合或在所有温度范围内在低浓度下用作摩擦减低剂。To a lesser extent, cellulose derivatives such as hydroxyethylcellulose, hydroxypropylcellulose and carboxymethylhydroxyethylcellulose are used with or without crosslinking agents. Xanthan gum and scleroglucan are two biopolymers that have been shown to have good proppant suspension capabilities, but are more expensive compared to guar gum derivatives and are therefore less commonly used. Polyacrylamide and polyacrylate polymers and copolymers are commonly used in high temperature applications or as friction reducers at low concentrations over all temperature ranges.
无聚合物的水基压裂流体可利用粘弹性表面活性剂获得。通常，这些流体通过混合适量的例如阴离子、阳离子、非离子与两性离子（Zwiterionic）等合适的表面活性剂制备。粘弹性表面活性剂流体的粘性归因于流体的成分所形成的三维结构。当粘弹性流体中的表面活性剂浓度显著超过临界浓度时，以及在存在电解液的多数情况下，表面活性剂分子聚集成为例如蠕虫状或杆状微团的物质，所述物质可相互作用以形成具有粘性与弹性的网络。Polymer-free water-based fracturing fluids are available using viscoelastic surfactants. Typically, these fluids are prepared by mixing appropriate amounts of suitable surfactants such as anionic, cationic, nonionic and zwiterionic. Viscoelastic Surfactants The viscosity of a fluid is due to the three-dimensional structure formed by the fluid's constituents. When the surfactant concentration in the viscoelastic fluid exceeds a critical concentration significantly, and in most cases in the presence of an electrolyte, the surfactant molecules aggregate into species such as worm-like or rod-like micelles that can interact to Form a sticky and elastic network.
此处和下文称为“支撑阶段”的所述方法的第二阶段涉及周期性地向压裂流体中引入固体颗粒或粒体形式的物质，以形成悬浮液。支撑阶段被分为两个周期性重复的子阶段，“载送子阶段”涉及注入不包含支撑剂的压裂流体；“支撑子阶段”涉及在压裂流体中添加支撑剂。含有粒体状支撑材料的泥浆的周期性击压的结果是，支撑剂不能完全充满裂缝。相反，间隔开的支撑剂团块形成柱状体，柱状体之间具有通道，地层流体通过该通道，如图2所示。支撑子阶段与载送子阶段时泵送的体积可不同。换言之，载送子阶段的体积可大于或小于支撑子阶段的体积。此外，这些子阶段的体积可随时间改变。换言之，与处理过程后期的支撑子阶段所泵送的体积相比，在处理过程前期的支撑子阶段可泵送更少的体积。子阶段的相对体积由工程人员根据需要多大裂缝的表面积被支撑剂团块支撑、以及多少裂缝面积是地层流体自由流动经过的敞开通道来选定。The second stage of the method, referred to here and hereinafter as the "propping stage", involves the periodic introduction of a substance in the form of solid particles or granules into the fracturing fluid to form a suspension. The propping phase is divided into two periodically repeating sub-phases, the "carrying sub-phase" which involves injecting fracturing fluid without proppant; the "propping sub-phase" which involves adding proppant to the fracturing fluid. As a result of periodic slugging of mud containing granular proppant material, the proppant cannot completely fill the fracture. Instead, spaced-apart proppant clusters form columns with channels between them through which formation fluids pass, as shown in FIG. 2 . The pumped volume may be different for the support sub-stage and the carrier sub-stage. In other words, the volume of the carrier sub-stage can be larger or smaller than the volume of the support sub-stage. Furthermore, the volumes of these sub-phases can change over time. In other words, the propped sub-stages earlier in the process may pump less volume than the propped sub-stages pumped later in the process. The relative volumes of the substages are selected by the engineer based on how much of the fracture's surface area needs to be supported by the proppant clusters, and how much of the fracture's area is an open channel through which formation fluids can flow freely.
在支撑阶段，加强和/或加固材料被引入压裂流体中，以增加所形成的支撑剂团块的强度，并防止它们在裂缝闭合的过程中坍塌。典型地，加强材料被添加到支撑子阶段，但是如下文可见并非总是需要如此。在整个支撑阶段以及从一个子阶段到另一子阶段，支撑材料和加强材料的浓度均可随时间改变。换言之，在两个随后的子阶段，加强材料的浓度可不同。在本方法的一些应用场合中，在整个支撑阶段、即在载送和支撑子阶段以连续方式引入加强材料也是合适的。换言之，加强材料的引入不是仅限于支撑子阶段。特别地，当加强材料的浓度在整个支撑阶段不变化、在支撑阶段期间单调增加或在支撑阶段期间单调减少时，可优选采用不同的实施方式。During the propping phase, reinforcing and/or reinforcing materials are introduced into the fracturing fluid to increase the strength of the formed proppant clusters and prevent them from collapsing during fracture closure. Typically reinforcement material is added to the support sub-stages, but as will be seen below this is not always required. The concentration of support material and reinforcement material can vary over time throughout the support phase and from one sub-phase to another. In other words, the concentration of reinforcing material may be different in two subsequent sub-phases. In some applications of the method it is also suitable to introduce the reinforcing material in a continuous manner throughout the supporting phase, ie in the carrying and supporting sub-phases. In other words, the introduction of reinforcing material is not limited to the support sub-stage. In particular, different embodiments may be preferred when the concentration of the reinforcing material does not change throughout the support phase, increases monotonically during the support phase or decreases monotonically during the support phase.
可固化或部分可固化的涂覆有树脂的支撑剂可用作加强和加固材料以形成支撑剂团块。用于特殊的井底静止温度（BHST）的合适的涂覆有树脂的支撑剂以及特殊的压裂流体的选择方法已为技术人员所熟知。此外，有机和/或无机纤维可加强支撑剂团块。这些材料可与涂覆有树脂的支撑剂组合使用或单独使用。这些纤维可被修改为仅具有粘合涂层；或具有涂覆有在通过裂缝时可溶于压裂流体中的非粘合物质层的粘合涂层。由粘合材料制成的纤维可用作加强材料，且涂覆有当在地下温度下通过裂缝时溶于压裂流体中的非粘合物质。金属颗粒为加强材料的另一优选方案，且可利用铝、含有可减少腐蚀的特殊添加剂的钢以及其它金属及合金等制成。金属颗粒可被成形为类似于球形且尺寸为0.1-4mm。优选地，金属颗粒采用长度大于2mm且直径为10至200微米的细长形状。此外，有机或无机物质、陶瓷、金属或金属基合金制成的板可用作加强材料。这些板可为盘形或矩形，且其长度和宽度使得对所有材料来说在三个维度中的任意两个维度之间的比例大于5：1。Curable or partially curable resin-coated proppants can be used as reinforcing and reinforcing materials to form proppant clusters. The selection of a suitable resin-coated proppant and a particular fracturing fluid for a particular bottom hole static temperature (BHST) is well known to the skilled artisan. Additionally, organic and/or inorganic fibers can strengthen the proppant cluster. These materials can be used in combination with resin-coated proppants or alone. These fibers can be modified to have only a bond coat; or to have a bond coat coated with a layer of a non-bond substance that is soluble in the fracturing fluid as it passes through the fracture. Fibers made of bonding material can be used as reinforcement material and coated with non-binding substances that dissolve in the fracturing fluid when passed through the fracture at subterranean temperatures. Metal particles are another preferred reinforcement material and can be made from aluminum, steel with special additives to reduce corrosion, and other metals and alloys. The metal particles can be shaped like a sphere and have a size of 0.1-4 mm. Preferably, the metal particles take an elongated shape with a length greater than 2 mm and a diameter of 10 to 200 microns. In addition, plates made of organic or inorganic substances, ceramics, metals or metal-based alloys can be used as reinforcing materials. The plates may be disc-shaped or rectangular and have a length and width such that the ratio between any two of the three dimensions is greater than 5:1 for all materials.
载送子阶段和支撑子阶段均可包括将试剂导入压裂流体中，以增加压裂流体的支撑剂传输能力。换言之，降低了支撑剂在压裂流体中的沉降率。试剂可以是具有长度远远超过其直径的细长颗粒的材料。该材料影响流变性质，并抑制流体中的对流，这导致支撑剂在压裂流体中的沉降率的下降。可使用的材料包括有机纤维、无机纤维、玻璃纤维、陶瓷纤维、尼龙纤维、碳素和金属纤维。支撑剂传输剂能在水基压裂流体或在井底流体中分解，例如基于聚乳酸、聚乙醇酸、聚乙烯醇等制成的纤维。纤维可涂覆有在地层温度下变成粘性的材料，或由所述材料制成。所述纤维可由涂覆有当通过裂缝时溶于压裂流体中的非粘合物质的粘合材料制成。根据三个维度中任意两个维度之间的比例大于5：1的主条件，所使用的纤维的长度不超过2mm且直径为10-200m。压裂流体中纤维材料的重量浓度为0.1至10%。Both the delivery sub-stage and the propping sub-stage may include introducing reagents into the fracturing fluid to increase the proppant transport capacity of the fracturing fluid. In other words, the settling rate of the proppant in the fracturing fluid is reduced. The reagent may be a material having elongated particles whose length far exceeds its diameter. The material affects the rheological properties and inhibits convection in the fluid, which results in a decrease in the proppant's settling rate in the fracturing fluid. Usable materials include organic fibers, inorganic fibers, glass fibers, ceramic fibers, nylon fibers, carbon and metal fibers. Proppant transport agents can disintegrate in water-based fracturing fluids or in downhole fluids, such as fibers based on polylactic acid, polyglycolic acid, polyvinyl alcohol, etc. The fibers may be coated with or made of materials that become viscous at formation temperatures. The fibers may be made of a binding material coated with a non-binding substance that dissolves in the fracturing fluid as it passes through the fracture. According to the main condition that the ratio between any two of the three dimensions is greater than 5:1, the length of the used fibers does not exceed 2mm and the diameter is 10-200m. The weight concentration of the fibrous material in the fracturing fluid is 0.1 to 10%.
当使用本发明的方法时，支撑剂选择是关键，应在考虑增加支撑剂团块强度的情况下进行选择。支撑剂团块在全裂缝闭合应力下应保持合理的残余厚度。该方法增加了流体通过在支撑剂团块之间形成的敞开通道的流入。在此情况下，支撑剂的渗透率值对使用该方法提高井的产量同样不是决定性的。因此，使用在本地层中对于标准水力压裂而言颗粒太弱的砂则可成功生成支撑剂团块。砂成本明显小于陶瓷支撑剂。此外，在裂缝闭合负载的施加期间，砂粒的破坏可增强由支撑剂粒体组成的相同团块的强度性能。这种情况的发生是因为支撑剂颗粒的破裂/破坏减小了团块孔隙，从而增加支撑剂紧密程度。砂泵送进入裂缝以产生支撑剂团块无需良好的粒度特性，即不需要窄的直径分布的颗粒。例如，为了实施上述方法，可使用50吨砂，其中10至15吨具有0.002至0.1mm的颗粒直径，15至30吨具有0.2至0.6mm的颗粒直径，10至15吨具有0.005至0.05mm的颗粒直径。应注意，以现有（传统的）水力压裂方法，需要比砂更贵的约100吨支撑剂来在所产生的裂缝中获得相似的水力传导率值。When using the method of the present invention, proppant selection is critical and should be selected with increasing proppant cluster strength in mind. The proppant cluster should maintain a reasonable residual thickness under the full fracture closure stress. This method increases the inflow of fluid through the open channels formed between the proppant clusters. In this case, the permeability value of the proppant is also not decisive for increasing the production of the well using this method. Thus, proppant clusters can be successfully generated using sands whose grains are too weak for standard hydraulic fracturing in the local formation. Sand costs significantly less than ceramic proppants. Furthermore, during the application of fracture closure loads, the failure of sand grains can enhance the strength properties of the same clumps composed of proppant grains. This occurs because fracture/destruction of the proppant particles reduces the cluster porosity, thereby increasing proppant compaction. Sand pumping into fractures to create proppant clusters does not require good particle size characteristics, ie, particles with a narrow diameter distribution. For example, to implement the above method, 50 tons of sand can be used, of which 10 to 15 tons have a particle diameter of 0.002 to 0.1 mm, 15 to 30 tons have a particle diameter of 0.2 to 0.6 mm, and 10 to 15 tons have a particle diameter of 0.005 to 0.05 mm. Particle diameter. It should be noted that with existing (traditional) hydraulic fracturing methods, about 100 tons of proppant, which is more expensive than sand, is required to obtain similar hydraulic conductivity values in the generated fractures.
为了本发明的目的，可优选使用仅具有粘合涂层的砂，或具有涂覆有当通过裂缝时可溶于压裂流体中的非粘合物质层的粘合涂层。非粘合物质保证粘性支撑剂颗粒在进入裂缝之前不会聚集，并使得可控制裂缝中的支撑剂颗粒获得其粘合特性时（处）的时刻（位置）。粘合涂层在地层温度下固化，且砂颗粒相互粘附。当地层流体流经团块时，团块内粘结的颗粒降低支撑剂团块腐蚀率，而且使支撑剂团块腐蚀破坏最小化。For the purposes of the present invention, it may be preferred to use sand with only a bond coat, or with a bond coat coated with a layer of a non-bond substance that is soluble in the fracturing fluid when passing through the fracture. The non-binding substance ensures that the cohesive proppant particles do not aggregate before entering the fracture and allows control of the moment (position) when (at) the proppant particles in the fracture acquire their adhesive properties. The bond coat cures at formation temperatures and the sand particles adhere to each other. As formation fluids flow through the clusters, the bonded particles within the clusters reduce proppant cluster corrosion rates and minimize proppant cluster corrosion damage.
在一些情况下，本发明的第一实施例可能需要支撑阶段之后的第三阶段，此处及后文称为“尾随阶段”，该阶段涉及连续地导入一定量的支撑剂。如果采用尾随阶段，则压裂处理的该阶段与传统的压裂处理相似，在该阶段将分选良好的传统支撑剂的连续层设置在裂缝中相当靠近井眼处。尾随阶段可涉及导入可增加流体的支撑剂传输能力的试剂和/或用作加强材料的试剂。所述尾随阶段与第二阶段区别在于，分选良好的支撑剂即具有大致均匀尺寸的颗粒的支撑剂的连续放置。支撑剂强度足以在经受裂缝闭合时产生的应力作用下防止其破裂（压碎）。在此阶段支撑剂的任务是防止裂缝闭合，因此在接近井眼处提供了良好的裂缝传导性。在该第三阶段使用的支撑剂应具有与传统支撑剂相似的特性。In some cases, the first embodiment of the present invention may require a third stage after the propping stage, here and hereinafter referred to as the "trailing stage", which involves the continuous introduction of a quantity of proppant. If a trailing stage is employed, this stage of the fracturing treatment is similar to a conventional fracturing treatment in that a continuous layer of well-sorted conventional proppant is placed in the fracture fairly close to the wellbore. The trailing phase may involve the introduction of reagents that increase the proppant transport capacity of the fluid and/or serve as reinforcing materials. The trailing phase is distinguished from the second phase by the sequential placement of well-sorted proppants, ie, proppants with particles of approximately uniform size. The proppant is strong enough to keep it from breaking (crushing) under the stresses of fracture closure. The task of the proppant at this stage is to prevent fracture closure, thus providing good fracture conductivity close to the borehole. The proppant used in this third stage should have properties similar to conventional proppants.
第二实施例second embodiment
在该实施例中，水力压裂方法将一种或多种试剂引入处理流体中，以在连续泵送支撑剂的同时促进泵送期间的裂缝中的支撑剂团块的形成。当试剂发生反应时，其导致支撑剂团块的局部形成。通常，试剂被选择或设计成使其反应或功能被延迟直至其被放置在裂缝内。延迟的化学和/或物理反应是水力压裂以及许多其它工业处理中常用的处理方法。可采用的一种处理方法是随着进入地球深处的较高温度地层而使压裂流体加热的试剂的简单温度激活。例如，当地面温度（surface temperature）为20摄氏度时，过硫酸铵均裂较为缓慢，但是在地层温度为100摄氏度时相对较快。第二处理方法为反应试剂或粘结剂的缓慢溶解。例如，聚乙烯醇在水中的溶解率取决于其分子量。反应物质的封装是水力压裂所采用的普通处理。由相对非反应的囊膜将反应材料或试剂与压裂流体隔开一段时间。根据许多不同方法，封装的材料随后或缓慢或快速地释放反应试剂。封装可被设计为通过溶解、机械腐蚀、压碎膨胀及破裂，或仅仅通过缓慢扩散释放其容纳物。用于受控的化学传送的释放机制的实例在许多专利和文献中均有描述。（美国专利No.5658861；4657784；5716923；5505740；5910322）。In this embodiment, the hydraulic fracturing method introduces one or more agents into the treatment fluid to promote the formation of proppant clusters in the fracture during pumping while the proppant is continuously pumped. When the reagents react, they result in the localized formation of proppant clusters. Typically, the reagent is selected or designed such that its response or function is delayed until it is placed within the fracture. Delayed chemical and/or physical reactions are common treatments in hydraulic fracturing, as well as many other industrial treatments. One treatment that may be employed is simple temperature activation of agents that heat the fracturing fluid as they enter higher temperature formations deep within the Earth. For example, ammonium persulfate homolysis is slow at a surface temperature of 20°C, but relatively fast at a formation temperature of 100°C. The second processing method is the slow dissolution of the reagent or binder. For example, the solubility rate of polyvinyl alcohol in water depends on its molecular weight. Encapsulation of reactive species is a common process employed in hydraulic fracturing. The reactive material or agent is separated from the fracturing fluid for a period of time by a relatively non-reactive capsule. The encapsulated material subsequently releases the reagents, either slowly or rapidly, according to a number of different methods. Encapsulations can be designed to release their contents by dissolution, mechanical erosion, crush expansion and rupture, or simply by slow diffusion. Examples of release mechanisms for controlled chemical delivery are described in numerous patents and literature. (US Patent Nos. 5,658,861; 4,657,784; 5,716,923; 5,505,740; 5,910,322).
本发明的该实施例涉及多个步骤。依照惯例，作为压裂处理的第一阶段的“充填阶段”时执行泵送。与支撑剂不连读地泵送的上述实施例不同，在本实施例中支撑剂（支撑剂）被连续地泵送。在支撑阶段，支撑剂的浓度可增加、保持恒定或下降。通常支撑剂浓度初始较低，并斜坡增长到附近处理终止时的较高浓度。本实施例的关键之处是，在支撑阶段，使得成核或支撑剂团块的形成的试剂非连续地或周期性地被引入压裂流体中。试剂被设计成仅在裂缝中小的区域或部位内起作用。该区域内的支撑材料被影响而使得它们形成团块、跨接并变得稳定。此外，在团块形成之后被泵送的支撑剂可积聚在团块上或使其尺寸增长。This embodiment of the invention involves several steps. Conventionally, pumping is performed during the "pack phase" as the first stage of a fracturing treatment. Unlike the above embodiments where the proppant is not pumped continuously, in this embodiment the proppant (proppant) is pumped continuously. During the propping phase, the concentration of proppant can increase, remain constant, or decrease. Typically the proppant concentration is initially low and ramped to a higher concentration near the end of the treatment. The key to this embodiment is that during the propping phase, agents that cause nucleation or formation of proppant clusters are introduced into the fracturing fluid either discontinuously or periodically. The reagents are designed to act only in a small area or site in the fracture. The support material in this area is affected such that they form clumps, bridge and become stable. In addition, proppant that is pumped after the agglomerate is formed can accumulate on the agglomerate or increase its size.
本发明的一种实施方式是通过局部降低流体的传输固相颗粒的能力来产生支撑剂团块。在这种情况下，试剂可以是高浓度的氧化“破胶剂”例如过硫酸铵，当在裂缝中不同位置处与压裂流体反应时，所述破胶剂将使压裂流体中的局部粘度产生剧烈、显著的下降。当流体粘度下降低于临界值时，压裂流体不能传输支撑剂颗粒，则颗粒停止、沉降并形成支撑剂团块。纤维的加入大大增强了支撑剂团块形成。图1显示了相对于支撑剂浓度的压裂流体的临界粘度。具有长的释放时间的封装的破胶剂可被用于支撑阶段开始时，具有短的释放时间的封装的破胶剂可被用于支撑阶段结束时。One embodiment of the present invention is to create proppant clusters by locally reducing the fluid's ability to transport solid phase particles. In this case, the agent may be a high concentration of an oxidizing "breaker" such as ammonium persulfate that, when reacted with the fracturing fluid at various locations in the fracture, will cause localized A sharp, noticeable drop in viscosity occurs. When the fluid viscosity drops below a critical value, the fracturing fluid is unable to transport the proppant particles, the particles stop, settle and form proppant clumps. The addition of fibers greatly enhanced proppant cluster formation. Figure 1 shows the critical viscosity of fracturing fluids versus proppant concentration. An encapsulated breaker with a long release time can be used at the beginning of the support phase and an encapsulated breaker with a short release time can be used at the end of the support phase.
加强材料例如纤维可大大增强支撑剂在裂缝壁之间局部卡塞以及形成团块的趋势。因此，在本实施例中，如上所述的纤维和/或其它加强材料可在支撑阶段或连续地或非连续地被加入压裂流体中（与破胶剂同时）。Reinforcing materials such as fibers can greatly enhance the proppant's tendency to locally jam and form clumps between fracture walls. Thus, in this embodiment, fibers and/or other reinforcing materials as described above may be added to the fracturing fluid (simultaneously with the breaker) during the propping stage either continuously or discontinuously.
对第一实施例中使用的支撑剂特性的要求也适用于第二实施例。可使用颗粒直径分布不窄的支撑剂，即每一颗粒具有相对较小的强度值的分选较差的支撑剂。例如，可以是具有与所述方法的第一实施例中所描述的涂层相似的涂层的砂颗粒。上述第三阶段也可出现。The requirements for the properties of the proppant used in the first embodiment also apply to the second embodiment. Proppants that do not have a narrow particle diameter distribution, ie, poorly sorted proppants that have relatively small strength values per particle, may be used. For example, it could be sand particles with a coating similar to that described in the first embodiment of the method. The third stage described above can also occur.
竞争性地粘结交联剂的化学物质可为用于局部降低流体粘度的另一类型的试剂。螯合剂（与锆酸盐交联剂反应）、山梨糖醇或聚乙烯醇（与硼酸盐交联剂反应）或使交联剂去活性的其它物质的局部释放可导致聚合物凝胶去交联并显著降低压裂流体粘性。由于许多交联反应与pH值相关，因此酸或碱的局部释放也可降低流体粘性。例如，通过引入封装的酸和/或物质的颗粒可调控压裂流体pH值，所述物质例如其中酸的释放或产生以受控比率发生的聚乳酸或聚乙醇酸。改变压裂流体pH值降低用于与聚合物形成稳定结合的交联剂的亲和力，且对于某些特定聚合物交联剂组合物来说流体的粘性下降。Chemicals that compete to bind the crosslinker may be another type of agent used to locally reduce the viscosity of a fluid. Topical release of chelating agents (reactive with zirconate cross-linkers), sorbitol or polyvinyl alcohol (reactive with borate cross-linkers), or other substances that deactivate cross-linkers can lead to deactivation of the polymer gel. Cross-links and significantly reduces fracturing fluid viscosity. Since many cross-linking reactions are pH dependent, topical release of acids or bases can also reduce fluid viscosity. For example, fracturing fluid pH can be adjusted by introducing encapsulated acids and/or particles of substances, such as polylactic acid or polyglycolic acid, in which acid release or production occurs at controlled rates. Changing the pH of the fracturing fluid reduces the affinity of the crosslinker for forming stable bonds with the polymer, and for certain polymer crosslinker compositions the viscosity of the fluid decreases.
为了所述目的，也可使用聚合物链交联剂的封装的吸收剂或竞争性螯合剂，其可允许受控的释放。对于硼酸盐可使用交联凝胶化学制品，例如葡萄糖酸钠或山梨糖醇。对于金属交联剂例如钛酸盐或锆酸盐，可使用的化学制品包括但不限于EDTA、NTA、磷酸盐、多乙酸乙烯酯。选择特定化学制品以攻击相应的交联剂对于技术人员来说众所周知，可借鉴参考文献，例如，R.M.Smith与A.E.Martell，Critical Stability Constants，第1-6卷，Plenum出版社，纽约，1974，1975，1976，1977，1982和1989。这种吸收剂可例如为磷酸盐或多乙酸乙烯酯。Encapsulated absorbers or competitive chelating agents of polymer chain cross-linkers can also be used for this purpose, which allow controlled release. For borates crosslinking gel chemicals such as sodium gluconate or sorbitol can be used. For metal crosslinkers such as titanates or zirconates, chemicals that can be used include, but are not limited to, EDTA, NTA, phosphates, polyvinyl acetates. The choice of a particular chemical to attack the corresponding cross-linker is well known to the skilled person, from references, e.g., R.M.Smith and A.E.Martell, Critical Stability Constants, vol. 1-6, Plenum Press, New York, 1974, 1975 , 1976, 1977, 1982 and 1989. Such absorbents may be, for example, phosphates or polyvinyl acetates.
通过降低压裂流体的局部粘度使支撑剂团块形成的试剂也可为与压裂流体反应以提供显著大的局部排热量的化学物质，所述显著大的局部排热量导致压裂流体受热并由此降低其局部粘度。这种物质的实例包括爆炸物或封装的活性金属例如钠，它们在裂缝中的各个位置释放物质，以在裂缝的整个长度形成支撑剂团块。（专利申请US2004/0226715Al：Willberg，Desroches等）。Agents that cause proppant cluster formation by reducing the local viscosity of the fracturing fluid may also be chemicals that react with the fracturing fluid to provide a significantly greater localized heat rejection that causes the fracturing fluid to heat and This reduces its local viscosity. Examples of such substances include explosives or encapsulated reactive metals such as sodium, which release substances at various locations in the fracture to form proppant clusters throughout the length of the fracture. (Patent application US2004/0226715Al: Willberg, Desroches et al.).
第三实施例third embodiment
第三实施例涉及通过降低裂缝中支撑剂的活动性形成支撑剂团块以及它们之间的通道。该方法涉及与第二实施例相似的第一和第二阶段，但不同之处在于，使团块形成的试剂降低支撑剂颗粒的活动性。A third embodiment involves the formation of proppant clusters and channels between them by reducing proppant mobility in fractures. This method involves first and second stages similar to the second embodiment, but differs in that the agglomerating agent reduces the mobility of the proppant particles.
这些添加剂可以是由于机械搅拌缓慢扩展且分散出单个纤维的纤维束。增加的纤维束已占体积（excluded volume）以及纤维浓度的局部增加可引发卡塞并产生支撑剂团块。These additives may be fiber bundles that slowly expand and disperse individual fibers due to mechanical agitation. Increased fiber bundle excluded volume and localized increases in fiber concentration can initiate sticking and create proppant clusters.
添加剂也可以是由具有“形状记忆”特性的合金制成的的切割的金属丝。例如铜-铝-镍（CuAlNi）形状记忆合金在许多石油和含气地层的温度范围上工作。这些材料可被弯曲以成形出小球体（弹簧）并在地面温度下保持其形状。当加热至储层温度，具有“形状记忆”的材料发生相变，随之恢复其原始记忆的直线形状。通过改变合金成分可改变相变温度。优选地，引入相变温度在各部分间发生变化的材料。在支撑阶段开始时，例如可合理地引入具有例如略低于地层温度的最高相变温度的材料；在第二阶段结束时，可合理地引入具有例如略高于地面流体温度的最低相变温度的材料。具有“形状记忆”的材料的球体的尺寸通常与支撑剂颗粒相似（K.Otsuka，C.M.Wayman，Shape memory materials，CambridgUniversity press，1999；欧洲专利0360319A1；美国专利5040283；美国专利5057114；美国专利6752208；美国专利4980960；美国专利4619320）。Additives may also be cut wires made of alloys with "shape memory" properties. For example copper-aluminum-nickel (CuAlNi) shape memory alloys work over the temperature range of many oil and gas formations. These materials can be bent to form small spheres (springs) that retain their shape at ground temperatures. When heated to reservoir temperatures, materials with "shape memory" undergo a phase transition, returning to their original memorized straight shape. The phase transition temperature can be changed by changing the alloy composition. Preferably, a material is introduced whose phase transition temperature varies from part to part. At the beginning of the propping phase, for example, it may be reasonable to introduce a material with the highest phase transition temperature, eg, slightly below the formation temperature; at the end of the second phase, it may be reasonable to introduce a material with, eg, slightly higher than the surface fluid temperature s material. Spheres of materials with "shape memory" are often of similar size to proppant particles (K. Otsuka, C.M. Wayman, Shape memory materials, Cambridge University press, 1999; European Patent 0360319A1; US Patent 5040283; US Patent 5057114; US Patent 6752208; US Patent 4,980,960; US Patent 4,619,320).
当金属球体经受裂缝中的升高温度时，它们恢复其原始形状，换言之所述球体伸直。如上所述，它们含量的局部增长有效地促进裂缝中支撑剂团块的形成。通过改变合金成分而逐渐改变形状恢复温度的能力使得可形成金属丝，因此形成了在裂缝的整个长度上均匀分布的不可移动的支撑剂团块。When the metal spheres are subjected to elevated temperatures in the fracture, they return to their original shape, in other words the spheres straighten. As mentioned above, local growth of their content effectively promotes the formation of proppant clusters in fractures. The ability to gradually change the shape recovery temperature by changing the alloy composition allows for the formation of wires, thus forming immovable clusters of proppant uniformly distributed over the entire length of the fracture.
该方法在其第三实施例中的实施也可规定使用超吸收材料以在流动的压裂流体中形成局部卡塞。超吸收剂例如交联聚丙烯酰胺丙烯酸脂共聚物可吸收它们在水中重量的100至300倍的水。可获得各种超吸收剂。针对本方法选择的一种特殊的吸收剂可由地层温度、用于制备压裂流体的水中的含盐量等等因素确定。Implementation of the method in its third embodiment may also provide for the use of superabsorbent material to create localized jams in the flowing fracturing fluid. Superabsorbents such as cross-linked polyacrylamide acrylate copolymers can absorb 100 to 300 times their weight in water. A variety of superabsorbents are available. The choice of a particular absorbent for this method may be determined by the temperature of the formation, the salt content of the water used to prepare the fracturing fluid, and the like.
本方法优选使用的是由壳体或乳剂保护的超吸收剂，所述壳体或乳剂当通过裂缝或压裂流体温度升高或这些条件的组合出现时溶解或散布。通过改变壳体厚度，可控制超吸收剂的一部分引入压裂流体与从壳体释放之间的时间间隔。当壳体溶解或散布时，吸收颗粒通过吸收周围的水分而开始增长。颗粒的质量和尺寸增加减弱了它们通过裂缝的移动，最终导致局部卡塞、捕获支撑剂颗粒，并形成支撑剂团块。The present method preferably uses a superabsorbent protected by a shell or emulsion that dissolves or spreads as it passes through the fracture or as the temperature of the fracturing fluid increases or a combination of these conditions occurs. By varying the casing thickness, the time interval between introduction of a portion of the superabsorbent into the fracturing fluid and release from the casing can be controlled. As the shell dissolves or spreads, the absorbent particles begin to grow by absorbing surrounding moisture. The increased mass and size of the particles impairs their movement through the fracture, eventually leading to localized sticking, trapping of proppant particles, and formation of proppant clusters.
在所述方法的第三实施例中，用于降低裂缝中支撑剂的活动性的添加剂可为在地层温度下其表面变成“粘性”的粒体、纤维或板。为实施该方法，可优选的是，使粘合表面具有可溶于压裂流体中的非粘合物质层的颗粒的附加涂层；通过改变物质厚度，可改变上述时间间隔，随着所述时间的逝去由于颗粒的表面粘合特性而导致形成支撑剂团块。用于控制时间间隔的另一技术采用在不同温度下得到粘合特性的涂层。为应用本技术，可优选在第二阶段开始时引入具有最大保护涂层厚度的颗粒（因此具有显示出“粘合特性”的最大温度）。而且，可优选在第二阶段结束时相应地引入具有最小保护涂层厚度的颗粒（因此具有显示出“粘合特性”的最小温度）。当这种颗粒进入裂缝时，它们相互碰撞（撞击）并粘附，从而形成支撑剂颗粒的聚集体。当聚集体尺寸变得与裂缝的特征宽度相当时，所述聚集体楔入裂缝面之间，导致局部支撑剂卡塞并形成支撑剂团块。In a third embodiment of the method, the additive used to reduce the mobility of the proppant in the fracture may be granules, fibers or plates whose surface becomes "sticky" at formation temperatures. To implement the method, it may be preferred that the bonding surface has an additional coating of particles of a layer of non-bonding substance soluble in the fracturing fluid; by varying the thickness of the substance, the above-mentioned time interval can be varied, with the The passage of time results in the formation of proppant clusters due to the surface binding properties of the particles. Another technique for controlling the time interval uses coatings that obtain adhesive properties at different temperatures. For the application of this technique, it may be preferable to introduce particles with maximum protective coating thickness (and thus maximum temperature at which "adhesive properties" are exhibited) at the beginning of the second stage. Furthermore, it may be preferable to accordingly introduce particles with a minimum protective coating thickness (and thus a minimum temperature exhibiting "adhesive properties") at the end of the second stage. When such particles enter the fracture, they collide (bump) and stick to each other, forming agglomerates of proppant particles. When the aggregate size becomes comparable to the characteristic width of the fracture, the aggregate is wedged between the fracture faces, causing localized proppant sticking and formation of proppant clusters.
如同方法的上述实施例，本实施例也可包括将加强材料引入压裂流体中，因此增加所形成支撑剂团块的强度；以及引入借助于降低支撑剂通过压裂流体的沉降率增大流体的支撑剂传输能力的试剂。支撑剂选择的所有这些要求，特别是强度相对适度的支撑剂的使用，颗粒尺寸的（可能的）宽分布，预先涂覆有在地层条件下可固化的粘结剂层的支撑剂仍适用于所述方法的本实施例。所述方法的上述第三阶段也是可能的。As with the above-described embodiment of the method, this embodiment may also include introducing a reinforcing material into the fracturing fluid, thereby increasing the strength of the formed proppant cluster; Reagents for proppant transport capabilities. All these requirements for proppant selection, in particular the use of relatively modest strength proppants, a (possibly) broad distribution of particle sizes, proppants pre-coated with a binder layer curable under formation conditions still apply This embodiment of the method. The above-mentioned third stage of the method is also possible.
第四实施例Fourth embodiment
水力压裂方法的第四实施例涉及通过将粘性有区别的两种流体顺序地泵送到井眼中形成支撑剂团块和位于支撑剂团块之间的通道。该方法涉及与上述实施例相似的第一阶段、以及将支撑剂连续地引入给定流体中的第二阶段。A fourth embodiment of a hydraulic fracturing method involves forming proppant clusters and channels between the proppant clusters by sequentially pumping two fluids of differing viscosities into the wellbore. The method involves a first stage similar to the above example, and a second stage in which proppant is continuously introduced into a given fluid.
与上述实施例相类似，第二阶段可能涉及将加强材料引入到压裂流体中，这些材料增大形成的支撑剂团块的强度；以及引入通过降低支撑剂沉降率增强流体的支撑剂传输能力的试剂。支撑剂选择的所有这些要求，特别是强度相对适度的支撑剂的使用，颗粒尺寸的宽分布，以及预先涂覆有在地层条件下可固化的粘结剂层仍适用于本实施例。Similar to the above example, the second stage may involve the introduction of reinforcing materials into the fracturing fluid that increase the strength of the formed proppant clusters; and the introduction of enhanced proppant transport capabilities of the fluid by reducing the proppant settling rate reagents. All of these requirements for proppant selection, particularly the use of proppants of relatively moderate strength, broad particle size distribution, and pre-coating with a binder layer curable under formation conditions still apply to this embodiment.
本方法的第三阶段停止注入含有支撑剂的压裂流体及其它材料，相反将非常低的粘度的流体注入所产生的裂缝中。由于它们的粘度之间的差异，在注入较高粘度流体之后注入低粘度流体导致较低粘度流体以“侵入物”的形式渗入到较高粘度流体中。这在充填裂缝的支撑剂中形成通道，从而将支撑剂分隔成离散团块，如图4所示。在图4所示的实施例中，流体的粘度比为80。The third stage of the method stops injection of proppant-containing fracturing fluid and other materials and instead injects a very low viscosity fluid into the created fracture. Due to the difference between their viscosities, injecting the low viscosity fluid after injecting the higher viscosity fluid results in the penetration of the lower viscosity fluid into the higher viscosity fluid in the form of "invasions". This creates channels in the proppant that fills the fracture, separating the proppant into discrete clusters, as shown in Figure 4. In the example shown in Figure 4, the fluid has a viscosity ratio of 80.
如同上述实施例，本方法可包括第四“尾随”阶段，所述第四“尾随”阶段涉及连续地将具有大致均匀颗粒尺寸的支撑剂、加强材料和/或具有增强压裂流体的支撑剂传输能力的细长颗粒的材料引入流体中。As with the above-described embodiments, the method may include a fourth "tail-up" stage that involves successively adding proppant having a substantially uniform particle size, reinforcing material, and/or proppant with enhanced fracturing fluid Elongated particles of transport capacity are introduced into the fluid.
上述用于水力压裂且具有形成支撑剂团块的不同机制的所有方法提供了非常高的水力裂缝传导率。这可通过在裂缝的整个长度和高度上形成间隔良好的强支撑剂团块产生。所述团块足够稳定以防止裂缝闭合；团块间通道具有足够大的供地层流体流动的横截面。All of the methods described above for hydraulic fracturing with different mechanisms of proppant cluster formation provide very high hydraulic fracture conductivity. This can be produced by the formation of well-spaced clusters of strong proppant throughout the length and height of the fracture. The agglomerates are sufficiently stable to prevent fracture closure; the inter-agglomerate channels have a cross-section large enough for formation fluids to flow.
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| CN2006800518207ACN101371005B (en) | 2006-01-27 | 2006-01-27 | Method for hydraulic fracturing of formations |
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