CN110792421A

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Info

Publication number: CN110792421A
Application number: CN201910681915.6A
Authority: CN
Inventors: 田福春; 陈紫薇; 赵玉东; 贾云鹏; 刘学伟; 李晓娟; 隋向云
Original assignee: Dagang Oilfield Group Co Ltd
Current assignee: China National Petroleum Corp; Dagang Oilfield Group Co Ltd
Priority date: 2019-07-26
Filing date: 2019-07-26
Publication date: 2020-02-14
Anticipated expiration: 2039-07-26
Also published as: CN110792421B

Abstract

The invention belongs to the field of oil field development, and particularly relates to a fracturing process for development and application of a hypotonic heterogeneous sandstone oil-gas layer, which comprises the following steps: 1) pumping slickwater and quartz sand or ceramsite into a reservoir stratum to form micro cracks, so as to improve the seepage capability of the stratum; 2) and (3) pumping the low-viscosity fracturing fluid and the ceramsite into the stratum in the main fracture stage of the long fracture created by the fracturing fluid to form the long fracture with high flow conductivity to communicate with the micro-fracture in the step 1), and establishing a near-wellbore high-permeability area to reduce the seepage pressure. The invention adopts a process method of slickwater filtration energy gain, fracturing fluid growth, high diversion main crack and large discharge capacity. Compared with the prior art adopting the jelly fracturing, the method greatly increases the swept volume of the fracture, and solves the problems of poor connectivity and poor seepage capability of the heterogeneous sandstone reservoir; the formation energy is supplemented; the high-flow-guide long crack is established, the stratum seepage field is improved, and the fracturing improvement effect is improved.

Description

Fracturing process for development and application of low-permeability heterogeneous sandstone oil-gas layer

Technical Field

The invention belongs to the field of oilfield development, and particularly relates to a fracturing process for development and application of a low-permeability heterogeneous sandstone oil-gas layer.

Background

The low-permeability heterogeneous sandstone oil-gas reservoir has poor physical properties, poor connectivity and low yield, can not produce normally, can be effectively developed only by modifying the reservoir, and improves the economic benefit.

The existing fracturing technology is applied to the transformation of the hypotonic heterogeneous sandstone oil-gas layer, the sweep range is small, the yield after fracturing is quickly decreased, the effect is not ideal, the requirement of reservoir transformation cannot be met, and the efficient development cannot be realized.

Disclosure of Invention

The invention aims to provide a fracturing process for development and application of a hypotonic heterogeneous sandstone oil-gas layer.

In order to achieve the purpose, the invention adopts the following technical scheme:

a fracturing process for the development and application of a hypotonic heterogeneous sandstone hydrocarbon reservoir comprises the following steps:

1) pumping slickwater and quartz sand or ceramsite into the stratum to form micro cracks, so as to improve the seepage capability of the stratum;

2) in the stage of making a main crack of the long crack by the fracturing fluid, pumping the low-viscosity fracturing fluid and the ceramsite into the stratum to form the long crack with high flow conductivity to communicate with the micro-crack in the step 1), establishing a near-wellbore high-permeability area, and reducing the seepage pressure;

the viscosity of the slickwater in the step 1) is 1.5-2mPa.s, the molecular weight of the resistance reducing agent is 600-800 ten thousand, the swelling time at normal temperature is not more than 90s, the salt tolerance is 30000mg/L, and the slickwater can be directly and continuously mixed.

The low viscous fluid in the step 2) is fracturing fluid with the viscosity of 30-50mPa.s, and can be directly and continuously mixed.

In the step 1), the quartz sand or the ceramsite is 70/140 meshes, the sand adding ratio is 5-20%, and the slug type sand adding is adopted.

In the step 1), the quartz sand or the ceramsite is 40/70 meshes, the sand adding ratio is 5-20%, and the sand is added in a slug type.

In the step 2), the ceramsite is one, two or three of 40/70 meshes, 30/50 meshes and 20/40 meshes. When more than two kinds of the proppant with the particle size are used simultaneously, the proppant with the small particle size is pumped firstly, and then the proppant with the large particle size is pumped; the sand adding ratio is 10-45%, and stepped continuous sand adding is adopted.

The total liquid amount of the slickwater and the low-viscosity fracturing fluid is more than or equal to 4000m3, wherein the slickwater accounts for 60-95% of the total liquid amount, and the low-viscosity fracturing fluid accounts for 5-40% of the total liquid amount.

The total sand content of the quartz sand or the ceramsite in the step 1) and the ceramsite in the step 2) is more than or equal to 200m³Wherein the quartz sand or the ceramsite accounts for 30-60% of the total sand in the step 1), and the ceramsite accounts for 40-70% of the total sand in the step 2).

The construction displacement of the step 1) and the step 2) is 7-10m 3/min.

The slickwater is a seawater-based slickwater fracturing fluid and comprises the following components, by the total weight of the seawater-based slickwater fracturing fluid, 0.05-0.15% of thickening agent, 0.01-0.03% of synergist, 0.1-0.2% of bactericide and the balance of seawater;

the low-viscosity fracturing fluid is a seawater-based fracturing fluid and comprises, by weight, 1% -2% of a thickening agent, 0.01% -0.03% of a synergist, 0.3% -0.5% of a cleanup additive, 0.1% -0.2% of a bactericide, 0.05% -0.1% of a gel breaker and the balance seawater.

The thickening agent is inverse emulsion polyacrylamide. The synergist is biodegradable iminodisuccinic acid sodium salt. The cleanup additive is an alkyl glycoside surfactant. The bactericide is dodecyl benzyl ammonium chloride. The gel breaker is ammonium persulfate or potassium persulfate. All products in this application are commercially available.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention adopts a process method of slickwater filtration energy gain, fracturing fluid growth, high diversion main crack and large discharge capacity. Compared with the prior art adopting the jelly fracturing, the method greatly increases the swept volume of the fracture, and solves the problems of poor connectivity and poor seepage capability of the heterogeneous sandstone reservoir; the formation energy is supplemented; the high-flow-guide long crack is established, the stratum seepage field is improved, and the fracturing improvement effect is improved.

(2) In the slickwater filtration and energization stage, high filtration loss of slickwater on a low-permeability heterogeneous sandstone oil-gas layer is utilized, large-displacement construction is combined, micro cracks are fractured along the same trend by means of generated net pressure and a cracked trend, the micro cracks are opened as far as possible, and the quartz sand is utilized to support the micro cracks to improve reservoir connectivity and supplement formation energy.

(3) In the stage of gel making long high-flow-guide main cracks, low-viscosity fracturing fluid is added with ceramsite. Long cracks with high flow conductivity are formed to communicate micro cracks formed in the filtration and energization stages of slickwater, so that the stratum seepage capability is improved, and the stratum seepage field is improved. Injecting the fracturing fluid and a large amount of sand with a high sand ratio, so that a high-flow-guide crack zone is formed in a zone close to a wellbore on the one hand; on the other hand, the net pressure in the fracture volume without proppant sedimentation is improved by utilizing the sedimentation effect of the ceramsite in the sand-carrying liquid and is kept until the construction is finished, so that the far well fractures are fully widened and extended, the reduction of the supporting height caused by the gradual closing of the stratum or the influence of the laying form of the proppant is reduced, the proppant forms effective fracture-forming height and supporting height in the far well, and the flow conductivity of the fractures at the far well is increased.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and preferred embodiments.

Example 1: well A in beach area, fractured well section 4362.4-4470.3 m and well deviation 63.2⁰. The span of a fracturing target layer is 107.9m, the 7 layers of a perforation well section are 55.7m, and the well logging interpretation permeability is 2.45 multiplied by 10^-3μm²-23.63×10^-3μm²Well test explains the effective permeability of 1.1X 10^-3μm²Indicating poor formation permeability. Optimizing fracturing process design and implementing total liquid amount of 4247m³Total sand amount 262m³Construction displacement of 7m³And/min. Wherein the low-viscosity slickwater accounts for 85 percent, the 70/140 quartz sand accounts for 31 percent, and the rest of the proppant is preferably 40/70 meshes and 30/50m meshes of combined ceramsite. The fracturing fluid adopts seawater-based slickwater and seawater-based low-viscosity fracturing fluid, and a continuous mixing mode is adopted on site. The well has remarkable implementation effect. The slick water is seaThe water-based slickwater fracturing fluid comprises the following components, by the total weight of the seawater-based slickwater fracturing fluid, 0.15% of thickening agent, 0.02% of synergist, 0.15% of bactericide and the balance of seawater; the low-viscosity fracturing fluid is a seawater-based fracturing fluid and comprises, by weight, 1% -2% of a thickening agent, 0.02% of a synergist, 0.4% of a cleanup additive, 0.15% of a bactericide, 0.08% of a gel breaker and the balance seawater.

Wherein the thickening agent is inverse emulsion polyacrylamide. The synergist is biodegradable iminodisuccinic acid sodium salt. The cleanup additive is an alkyl glycoside surfactant. The bactericide is dodecyl benzyl ammonium chloride. The gel breaker is ammonium persulfate or potassium persulfate.

The results are shown in table 1 for the before and after effects.

TABLE 1

The technology is applied 71 times aiming at the low-permeability heterogeneous sandstone hydrocarbon reservoir, and remarkable application effects are achieved.

The above description is only a preferred embodiment of the present invention, and for those skilled in the art, the present invention should not be limited by the description of the present invention, which should be interpreted as a limitation.

Claims

1. A fracturing process for development and application of a hypotonic heterogeneous sandstone oil-gas layer is characterized by comprising the following steps:

1) pumping slickwater and quartz sand or ceramsite into a reservoir stratum to form micro cracks, so as to improve the seepage capability of the stratum;

2) and (3) pumping the low-viscosity fracturing fluid and the ceramsite into the stratum in the main fracture stage of the long fracture created by the fracturing fluid to form the long fracture with high flow conductivity to communicate with the micro-fracture in the step 1), and establishing a near-wellbore high-permeability area to reduce the seepage pressure.

2. The fracturing process for the development and application of the hypotonic heterogeneous sandstone oil-gas layer according to claim 1, wherein the viscosity of the slickwater in the step 1) is 1.5-2mPa.s, the molecular weight of the friction reducer is 600-800 ten thousand, the swelling time at normal temperature is not more than 90s, and the salt tolerance is 30000mg/L, so that the fracturing process can be directly and continuously mixed.

3. The fracturing process of claim 1, wherein the low viscosity fluid of step 2) is a fracturing fluid with a viscosity of 30 to 50mpa.s, and can be directly and continuously mixed.

4. The fracturing process of the development and application of the hypotonic heterogeneous sandstone oil-gas layer according to claim 1, wherein the quartz sand or ceramsite in step 1) is 70/140 meshes, the sand adding ratio is 5% -20%, and the sand is added in a slug manner.

5. The fracturing process of the development and application of the hypotonic heterogeneous sandstone oil-gas layer according to claim 1, wherein the quartz sand or ceramsite in the step 1) is 40/70 meshes, the sand adding ratio is 5-20%, and the sand is added in a slug type.

6. The fracturing process for the development and application of the hypotonic heterogeneous sandstone oil and gas layer according to claim 1, wherein the ceramsite in the step 2) is one, two or three of 40/70 meshes, 30/50 meshes and 20/40 meshes. When more than two kinds of the proppant with the particle size are used simultaneously, the proppant with the small particle size is pumped firstly, and then the proppant with the large particle size is pumped; the sand adding ratio is 10-45%, and stepped continuous sand adding is adopted.

7. The fracturing process of claim 1, wherein the total fluid volume of slickwater and low-viscosity fracturing fluid is more than or equal to 4000m3, wherein slickwater accounts for 60-95% of the total fluid volume, and low-viscosity fracturing fluid accounts for 5-40% of the total fluid volume.

8. The device of claim 1, whereinThe fracturing process for development and application of the heterogeneous sandstone oil-gas layer is characterized in that the total sand content of the quartz sand or the ceramsite in the step 1) and the ceramsite in the step 2) is more than or equal to 200m³Wherein the quartz sand or the ceramsite accounts for 30-60% of the total sand in the step 1), and the ceramsite accounts for 40-70% of the total sand in the step 2).

9. The fracturing process of the development and application of hypotonic heterogeneous sandstone oil and gas reservoir of claim 1, wherein the construction displacement of step 1) and step 2) is 7-10m 3/min.