US20090229826A1 - Hydrocarbon Sweep into Horizontal Transverse Fractured Wells - Google Patents

Abstract

The present invention is directed to a method of increasing hydrocarbon production in an existing well in a hydrocarbon reservoir. The method includes the steps of forming a substantially horizontal transverse fractured wellbore that intersects the existing well and injecting a fluid remote from the existing well so as to form a fluid front that sweeps the hydrocarbons into the horizontal transverse fractured wellbore. Successive fractures can be sealed to control propagation of the fluid front and delay infiltration of the fluid into the production.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application is a divisional patent application of commonly-owned U.S. patent application Ser. No. 11/003,804, filed Dec. 2, 2004, entitled “Hydrocarbon Sweep Into Horizontal Transverse Fractured Wells,” by Loyd E. East Jr., et al., which is incorporated by reference herein for all purposes.
BACKGROUND
• The present invention relates generally to hydrocarbon production, and more particularly to a method of increasing hydrocarbon production in an existing well by forming a substantially horizontal transverse fractured wellbore, which intersects the existing well and injecting a fluid into the reservoir to sweep the hydrocarbons into the substantially horizontal transverse fractured wellbore.
• In certain subterranean formations, fluid is injected into the reservoir to displace or sweep the hydrocarbons out of the reservoir. This method of stimulating production is sometimes referred to as a method of “Enhanced Oil Recovery” and may be called waterflooding, gasflooding, steam injection, etc. For the purpose of this specification, the general process will be defined as injecting a fluid (gas or liquid) into a reservoir in order to displace the existing hydrocarbons into a producing well. The primary issue with injecting fluid to enhance oil recovery is how to sweep the reservoir of the hydrocarbon in the most efficient manner possible. Because of geological differences in a reservoir, the permeability may not be homogenous. Because of such permeability differences between the vertical and horizontal directions or the existence of higher permeability streaks, the injecting fluid may bypass some of the reservoir and create a path into the producing well.
• The industry has come up with numerous methods to improve the sweep efficiency and the overall reservoir that is swept by individual wells. These methods include fracturing and the use of horizontal wells. The industry currently uses horizontal wells as injectors in an attempt to expose more of the reservoir to the injecting fluid. The goal is to create a movement of injection fluid evenly across the reservoir. This is sometimes referred to as line drive. The industry also uses horizontal wells as producers, again the goal being to evenly produce the reservoir so to form a line drive.
• SPE Paper 84077 presents a method referred to as toe-to-heel waterflooding where a horizontal lateral is used to produce the reservoir with a vertical injector located nearer the toe (end) of the lateral. The method referred to in this paper is limited, since the horizontal lateral only covers a limited area in the reservoir. It therefore does not maximize the amount of surface area that can be used to recover the hydrocarbons. This method also suffers from an inability to control the influx of injection fluid at the toe to improve recovery.
• Part of the efficiency of the sweep is reducing the production of the injection fluid. The industry has created several techniques from the use of chemicals that block the injection fluid, to injection fluids that improve the matrix flow through the reservoir to reduce channeling. Some injection programs include attempts to plug high permeability streaks and natural fractures in the reservoir. This is done to force the injection fluid out into more of the reservoir to displace hydrocarbons.
• When the injection fluid is produced, such as water, it is usually removed from the hydrocarbons at the surface using multi-phase separation devices. These devices operate to agglomerate and coalesce the hydrocarbons, thereby separating them from the water. A drawback of this approach, however, is that no separation process is perfect. As such, some amount of the hydrocarbons always remains in the water. This can create environmental problems when disposing of the water, especially in off-shore applications. Also, the multi-phase separation devices are rather large in size, which is another disadvantage in off-shore applications, as space is limited. Yet another drawback is that these devices can require additional maintenance or repair if solids are part of the produced fluid stream. A further, and perhaps greatest drawback of these solutions, is that they do nothing to increase or maximize the amount of hydrocarbons being produced. Their only focus is removing the water from the production.
• Specialized downhole tools have also been developed, which separate the water from the hydrocarbons downhole. These tools are designed to leave the water in the formation as the hydrocarbons are produced. While these devices can remove a significant amount of water from the hydrocarbons, they are also often less than perfect in removing the water from the hydrocarbons. They also suffer from the same drawback of the surface separation devices in that they do nothing to increase or maximize the amount of hydrocarbons being produced.
• A solution is therefore desired that not only improves the efficiency and economics of enhanced oil recovery through injection, but that also reduces the amount of injection fluid that infiltrates the hydrocarbon production of an existing well.
SUMMARY
• The present invention is directed to a method of increasing hydrocarbon production in an existing well in a hydrocarbon reservoir, which minimizes the drawbacks of prior art methods and apparatuses. In one embodiment, the method includes the steps of forming a substantially horizontal transverse fractured wellbore; and injecting a fluid in the reservoir so as to form a fluid front that sweeps the hydrocarbons into the horizontal transverse fractured wellbore.
• In another embodiment, the method according to the present invention includes the steps of drilling a substantially horizontal wellbore that intersects the existing well and forming at least one transverse fracture in the reservoir along the substantially horizontal wellbore. In one exemplary embodiment, a plurality of transverse fractures are formed. The method further includes the steps of drilling an injection well into the reservoir and injecting a fluid into the reservoir through the injection well so as to sweep the hydrocarbons toward the plurality of transverse fractures. The hydrocarbons can then be drained into the plurality of transverse fractures.
• In another embodiment, the method according to the present invention includes the steps of drilling a substantially horizontal wellbore that intersects the existing well, forming a plurality of transverse fractures in the reservoir along the substantially horizontal wellbore, and installing a tubing in the substantially horizontal wellbore with an end of the tubing being disposed at a toe portion of the substantially horizontal wellbore, downhole of the farthest transverse fracture. The terms “downhole” and “uphole” are defined herein to describe locations away from and toward, respectively, the existing well. In other words, one object which is downhole of another is farther away from the existing well than the other object and one object which is uphole of another is closer to the existing well than the other object. This embodiment further includes the steps of installing a packer between the tubing and a sidewall forming the substantially horizontal wellbore uphole of the farthest transverse fracture, injecting a fluid into the reservoir through the end of the tubing at the toe of the substantially horizontal wellbore to sweep the hydrocarbons toward the plurality of transverse fractures, and draining the hydrocarbons into the plurality of transverse fractures. No separate injection well is drilled with this embodiment.
• In yet another embodiment, the method according to the present invention includes the steps of drilling a first substantially horizontal wellbore that intersects the existing well and forming a plurality of transverse fractures in the reservoir along the first substantially horizontal wellbore. This method also includes the steps of drilling a second substantially horizontal wellbore that intersects the existing well, and forming at least one transverse fracture in the reservoir along the second substantially horizontal wellbore. This method further includes the steps of sealing the at least one transverse fracture formed along the second substantially horizontal wellbore and draining the hydrocarbons into the plurality of transverse fractures formed along the first substantially horizontal wellbore.
• In yet another embodiment, the method according to the present invention includes the steps of drilling a pair of oppositely disposed substantially horizontal injection wellbores that intersect the existing well, drilling a plurality of substantially horizontal producing wellbores that intersect the existing well and are disposed between the injection wellbores and forming a plurality of transverse fractures in the reservoir along each of the plurality of substantially horizontal producing wellbores. The method further includes the step of injecting a fluid into the reservoir from the pair of oppositely disposed substantially horizontal injection wellbores and draining the hydrocarbons into the plurality of transverse fractures formed along the plurality of substantially horizontal producing wellbores.
• In still another embodiment, the method according to the present invention includes the steps of drilling a pair of oppositely disposed substantially horizontal injection wellbores that intersect the existing well, drilling a pair of oppositely disposed substantially horizontal producing wellbores that intersect the existing well and are disposed between the injection wellbores, each producing wellbore being formed with a plurality of laterals, and forming a plurality of transverse fractures in the reservoir along each of the plurality of laterals. This method further includes the steps of injecting a fluid into the reservoir from the pair of oppositely disposed substantially horizontal injection wellbores and draining the hydrocarbons into the plurality of transverse fractures formed along the plurality of laterals.
• In another embodiment, the transverse fractures along the wellbore are created in stages during the production of the well rather than at the outset. For example, a transverse fracture at the toe is created and produced, then another transverse fracture is created uphole and injection fluid is pumped into the end fracture to sweep the formation between the two fractures. After a period of time either scheduled or determined by performance of the well more transverse fractures can be added along the wellbore to sweep more of the formation intersected by the lateral.
• As part of these embodiments using transverse fractures, the flow from the transverse fractures is controlled by injecting chemicals into the transverse fractures to seal or partially seal the fracture in order to reduce the movement of the injection fluid into the fracture and force the injection fluid out into the reservoir away from the wellbore so as to increase the sweep area.
• The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the exemplary embodiments, which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
• A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, which:
• FIG. 1 is a schematic diagram illustrating one embodiment of the present invention wherein one transverse fracture in the substantially horizontal wellbore is at least partially sealed and fluid injected from a separate injection well sweeps the hydrocarbons into the remaining transverse fractures.
• FIG. 2 is the embodiment illustrated inFIG. 1 wherein a second transverse fracture has been at least partially sealed to slow the progression of the fluid front.
• FIG. 3 is a schematic diagram illustrating another embodiment of the present invention wherein a tubing is used to inject a flood fluid into the reservoir.
• FIG. 4 is a modification of the embodiment illustrated inFIG. 1 wherein one of the transverse fractures is sealed and the tubing injects a flood fluid into the formation to sweep the hydrocarbons into the remaining transverse fractures.
• FIG. 5 is another embodiment of the present invention wherein two opposing substantially horizontal wellbores are drilled one of which acts as an injection well the other of which removes the hydrocarbons through a plurality of transverse fractures.
• FIG. 6 is yet another embodiment of the present invention wherein a pair of opposed substantially horizontal injection wells inject fluid into the formation so as to sweep hydrocarbons into a plurality of substantially horizontal producing wellbores formed with a plurality of transverse fractures with the sweep direction of the hydrocarbon flow being toward the existing well.
• FIG. 7 is yet another embodiment of the present invention wherein a pair of opposed substantially horizontal injection wells inject fluid into the formation so as to sweep hydrocarbons into a plurality of substantially horizontal producing wellbores formed with a plurality of transverse fractures with the sweep direction of the hydrocarbon flow being away from the existing well.
• FIG. 8 is yet another embodiment of the present invention wherein a pair of opposed substantially horizontal injection wells inject fluid into the formation so as to sweep hydrocarbons into a pair of opposed substantially horizontal wellbores having a plurality of laterals formed with a plurality of transverse fractures with the sweep direction of the hydrocarbon flow being toward the existing well.
• FIGS. 9A and 9B illustrate yet another embodiment of the present invention wherein a fracture is created in the toe of a horizontal lateral through which hydrocarbons are initially produced, and wherein subsequent transverse fractures are created progressively closer to the existing well and previously formed transverse fractures are sealed as unacceptable levels of non-hydrocarbons are produced.
DETAILED DESCRIPTION
• The details of the present invention will now be described. The present invention is directed to a method of increasing hydrocarbon recovery from an existing well through injecting fluid to displace the hydrocarbons from the reservoir while simultaneously reducing the influx of water and other non-hydrocarbon fluids, such as carbon dioxide, into the existing well. In its most basic form, the present invention achieves its goal by providing at least one substantially horizontal wellbore having a plurality of transverse fractures, sealing at least one of the transverse fractures and injecting a flood fluid, such as water, into the formation so as to force the hydrocarbons into the remaining transverse fractures. As those of ordinary skill in the art will appreciate from the disclosure that follows, there are many different ways of arranging the substantially horizontal wells, many different ways of injecting the fluid into the formation, and many different ways of recovering the hydrocarbons into the transverse fractures. A number of exemplary ways of performing these functions are disclosed herein.
• Turning toFIG. 1, a well configuration formed using one exemplary method according to the present invention is illustrated. In this embodiment, a substantiallyhorizontal wellbore110 is drilled intohydrocarbon reservoir112 from existing well100. Substantiallyhorizontal wellbore110 can be drilled using conventional directional drilling techniques or other similar methods. The precise method used is not critical to the present invention. In one certain exemplary embodiment, thewellbore110 is lined with acasing string114. Thecasing string114 may then be cemented to the formation. There are a number of factors that go into the decision of whether or not to case thewellbore110 and whether or not to cement thecasing114 to the formation. A person of ordinary skill in the art should know whether thewellbore110 needs to be cased. In most cases, it will be beneficial to do so.
• Next, a plurality oftransverse fractures116 are formed along thehorizontal wellbore110. Thetransverse fractures116 are formed along the natural fracture line and generally parallel to one another. There are a number of different ways of carrying out this step. In one exemplary embodiment, the plurality oftransverse fractures116 are formed by using a hydra jetting tool, such as that used in the SurgiFrac® fracturing service offered by Halliburton Energy Services. In this embodiment, the hydra jetting tool forms each fracture of the plurality oftransverse fractures116 one at a time. Eachtransverse fracture116 is formed by the following steps: (i) positioning the hydra jetting tool in the substantiallyhorizontal wellbore110 at the location where thetransverse fracture116 is to be formed, (ii) perforating thereservoir112 at the location where thetransverse fracture116 is to be formed, and (iii) injecting a fracture fluid into the perforation at sufficient pressure to form atransverse fracture116 along the perforation. As those of ordinary skill in the art will appreciate, there are many variations on this embodiment. For example, fracture fluid can be simultaneously pumped down the annulus while it is being pumped out of the hydra jetting tool to initiate the fracture or not. Alternatively, the fracturing fluid may be pumped down the annulus and not through the hydra jetting tool to initiate and propagate the fracture, i.e., in this version the hydra jetting tool only forms the perforations.
• In another version of this embodiment, the plurality oftransverse fractures116 are formed by staged fracturing. Staged fracturing is performed by (i) detonating a charge in the substantiallyhorizontal wellbore110 at the location where atransverse fracture116 is to be formed so as to form a perforation in the reservoir at that location, (ii) pumping a fracture fluid into the perforation at sufficient pressure to propagate thetransverse fracture116, (iii) installing a plug in the substantially horizontal well110 bore uphole of thetransverse fracture116, (iv) repeating steps (i) through (iii) until the desired number oftransverse fractures116 have been formed; and (v) removing the plugs following the completion of step (iv). As those of ordinary skill in the art will appreciate, there are many variants on the staged fracture method.
• In yet another version of this embodiment, the plurality oftransverse fractures116 are formed using a limited entry perforation and fracture technique. The limited entry perforation and fracture technique is performed by (i) lining the substantiallyhorizontal wellbore110 with acasing string114 having a plurality of sets of predrilled holes arranged along its length, and (ii) pumping a fracturing fluid through the plurality of sets of predrilled holes in the casing string at sufficient pressure to fracture thereservoir112 at the locations of the sets of predrilled holes.
• In still another version of this embodiment, the plurality oftransverse fractures116 are formed by the steps of (i) installing a tool having a plurality of hydra jets formed along its length into the substantiallyhorizontal wellbore110, and (ii) pumping fluid through the plurality of hydra jets simultaneously at one or more pressures sufficient to first perforate and then fracture thereservoir112 at the locations of the hydra jets.
• After the substantiallyhorizontal wellbore110 has been cased and the plurality oftransverse fractures116 have been formed, the transverse fracture farthest from the existing well100 is sealed. The sealant is installed into the transverse fracture farthest from the existing well100 by squeezing it into the transverse fracture. This is accomplished by first isolating the perforations adjacent to the fracture using a packer135 (such as a hydraulically set drillable, retrievable or inflatable packer) on the end of tubing and set in the casing; then pumping the sealant in a fluid state through the tubing, then through the perforations and into the transverse fracture to be sealed until a sufficient volume of sealant has been placed into the transverse fracture to accomplish the barrier to flow by the invading waterflood.
• The sealant can be a cement, a linear polymer mixture, a linear polymer mixture with cross-linker, an in-situ polymerized monomer mixture, a resin-based fluid, an epoxy based fluid, or a magnesium based slurry. All of these sealants are capable of being placed in a fluid state with the property of becoming a viscous fluid or solid barrier to fluid migration after or during placement into the fracture. In one embodiment, the sealant is H₂Zero™. Other sealants could include particles, drilling mud, cuttings, and slag. Exemplary particles could be ground cuttings so that a wide range of particle sizes would exist producing low permeability as compared to the surrounding reservoir.
• An injection well120 is then drilled remote from, but generally parallel to, existing well100. In one certain embodiment, injection well120 is drilled proximate the sealedtransverse fracture116. As those of ordinary skill in the art will appreciate, the injection well120 can alternatively be formed prior to the formation of the substantiallyhorizontal wellbore110. Once the injection well120 has been formed and the transverse fracture farthest from the existing well100 sealed, flood fluid can be pumped down the injection well120. As the flood fluid is pumped into thereservoir112 it forms a propagatingflood front130. Theflood front130 is diverted around the sealed transverse fracture, as indicated inFIG. 1 by the large arrows. At the same time, hydrocarbons are drained into thetransverse fractures116, as indicated inFIG. 1 by the small arrows. As the adjacent transverse fracture begins producing high rates of flood fluid, it is sealed and abridge plug135 is installed in the substantiallyhorizontal wellbore110 just uphole of the adjacent transverse fracture, as illustrated inFIG. 2.Bridge plug135 may be a mechanical bridge plug that is either drillable or retrievable. Alternatively, a plug made of particulate matter, e.g., sand or diverting agent can be used. In yet another embodiment, theplug135 is formed of a removable viscous fluid. This isolation process is repeated as sufficiently high flood fluid ratios are being produced from successive transverse fractures until all of the transverse fractures have been sealed.
• In one exemplary variant of the method illustrated inFIG. 1, the transverse fracture is only partially sealed in the near wellbore area rather than completely sealed all the way to its tip. The benefit of sealing the near wellbore area is that if the injection fluid happens to move faster in this area the flow of injection fluid can be partially diverted to improve sweep.
• In another exemplary embodiment, a new transverse fracture is created during the sealing process in the near wellbore area. One method of pumping the sealing material is to use the SurgiFrac® fracturing service available from the assignee herein. If this process is used, then a fracture can be created and sealed in one step without the need of mechanical isolation.
• In yet another variant of the method illustrated inFIG. 1, the transverse fracture nearest thetoe140 of the substantially horizontal wellbore is not sealed initially. Rather, it initially produces hydrocarbons. However, because the depletion of pressure resulting from hydrocarbon production in the substantiallyhorizontal wellbore110 encourages theflood front130 to move in the direction of thehorizontal wellbore110, eventually theflood front130 reaches thetoe140. When sufficiently high flood fluid ratios are being produced, a drillable packer is positioned between the transverse fracture nearest thetoe140 and the transverse fracture adjacent thereto. This isolates the transverse fracture nearest the toe from producing into the substantiallyhorizontal wellbore110 and the highly conductive fracture allows the flooding fluid to be distributed along the fracture. As the adjacent fracture begins producing high rates of flood fluid, this isolation process is repeated.
• Another alternative method to setting packers includes installing a plug made of cement or other material that sets. The plug in the wellbore thus may be the same chemical or material used to seal the transverse fractures.
• In one certain embodiment, adevice150 for monitoring the amount of infiltration of the flood fluid into the hydrocarbons being produced in the substantiallyhorizontal wellbore110 is installed adjacent to one or more of the fractures that have not been sealed. Examples of such devices include, but are not limited to, fluid flow meters, electric resistivity devices, oxygen decay monitoring devices, fluid density monitoring devices, pressure gauge devices, and temperature monitoring devices. Data from these devices can be obtained through electric lines, fiber-optic cables, retrieval of bottom hole sensors or other methods common in the industry. Another solution involves installing a sampling line into the production flow path. This could be a tubing (coiled or jointed) that takes a sample of the fluid at a point in the wellbore. If the sampling line is continuous tubing, then the well can be continuously monitored. In yet another embodiment, a sampling chamber is formed in the production flow path so that discrete samples of fluid can be taken. With such devices/solutions, the percentage of injection fluid to hydrocarbons can be measured at the surface, so that a judgment can be made whether to close a transverse fracture.
• Turning toFIG. 3, another embodiment of the method for increasing hydrocarbon production in accordance with the present invention is disclosed. In this embodiment, the flood fluid is introduced into thereservoir112 through atubing160, which is installed into the substantiallyhorizontal wellbore110 rather than a separate injection well. Thetubing160 injects the flood fluid into thereservoir112 from thetoe140 of the substantiallyhorizontal wellbore110. Hydrocarbons are produced up theannulus165 formed between thetubing160 and thecasing114.Packer170 seals the end of thetubing160, so the flood fluid does not enter into theannulus165. Once the flood fluid ratio reaches a sufficiently high value, the transverse fracture nearest thetoe140 is sealed using the techniques described above. This process is repeated for successivetransverse fractures116 as theflood front130 moves toward the existing well100 and the flood fluid ratio begins to increase beyond an acceptable level. In a variant of this embodiment, thetransverse fracture116 closest to thetoe140 is sealed before the flood fluid is injected into thereservoir112, as shown inFIG. 4.
• Turning toFIG. 5, yet another embodiment of the method in accordance with the present invention is illustrated. In this embodiment, two opposing substantiallyhorizontal wellbores510 and511 are drilled intohydrocarbon reservoir512 using conventional directional drilling techniques. Substantiallyhorizontal wellbore510 is cased withcasing string514 using conventional casing techniques. Substantiallyhorizontal wellbore510 is also formed with a plurality of generally paralleltransverse fractures516 using any one of the techniques described above. Substantiallyhorizontal wellbore511 may or may not be cased withcasing string515 depending upon the condition of the reservoir. At least onetransverse fracture517 is formed at thetoe section540 of substantiallyhorizontal wellbore511. This is accomplished by first isolating the perforations adjacent to thefracture using packer570 on the end of thetubing560 and setting it in the casing. Then, the sealant is pumped in a fluid state through thetubing560, then through the perforations and into the fracture to be sealed until a sufficient volume of sealant has been placed into the fracture to accomplish the barrier to flow by the invading waterflood.
• Fluid is injected into thereservoir512 throughtoe section540 of substantiallyhorizontal wellbore511 through the end oftubing560.Flood front530 propagates outward in the direction indicated by the arrows inFIG. 5. The sealedtransverse fracture517 helps to direct the fluid front in a manner which promotes drainage of the hydrocarbons intotransverse fracture516. As the flood fluid ratio reaches an unacceptably highlevel transfer fractures517 are successfully sealed starting with transverse fracture closest to existing well500 and moving downhole towardtransverse fracture516 closest to the toe portion of substantiallyhorizontal wellbore510.
• A device for monitoring the amount of non-hydrocarbon fluid in thehydrocarbon production550 may also be employed in substantiallyhorizontal wellbore510. The hydrocarbon production flows in the direction of the arrows moving up the annulus and wellbore510 into existingwellbore500.
• Turning toFIG. 6, another embodiment of the method in accordance with the present invention is illustrated. In this embodiment a pair of opposinghorizontal wellbores601 and602 formed using known techniques. Once formed,wellbores601 and602 can be used to inject a flood fluid intoreservoir612. In this embodiment a plurality of substantiallyhorizontal wellbores620 through629 are disposed between opposed substantiallyhorizontal injection wellbores601 and602. Each of the substantiallyhorizontal production wellbores620 through629 has a plurality oftransverse fractures616 formed using any of the techniques described above. Each of the substantiallyhorizontal production wellbores620 through629 may be cased with the casing614. As those of ordinary skill in the art will appreciate, the exact number of wellbores in the pattern can vary depending upon the conditions of the reservoir.
• In one embodiment, the transverse fractures farthest downhole from existing well600 are all sealed and plugged with drillable plugs635. The opposing substantiallyhorizontal injection wells601 and602 may or may not be cased depending upon the nature of thereservoir612. Those of ordinary skill in the art will appreciate those circumstances under which wellbore601 and602 should be cased.Tubing660 and662 are inserted respectively intowellbore601 and602. Flood fluid is injected intoreservoir612 through the ends oftubing660 and662 and the toe sections ofwellbore601 and602. In this embodiment, the flood front sweeps inward toward the existing well600. As the fluid flood ratio increases with the hydrocarbon production, over time successive transverse fractures uphole from the sealed fractures at the toes ofhorizontal wells620 through629 can be sealed to reduce the production of flood fluids. This process can be repeated until all of the transverse fractures have been sealed. In the embodiment ofFIG. 6, flood fluid is introduced via tubing and produced up annuluses formed in thehorizontal production wells620 through629.
• Turning toFIG. 7 a variant of the embodiment of the method according to the present invention illustrated inFIG. 6 is shown. In this embodiment, the sweep of the flood front is from the existing well outward, i.e., it is an outward sweep. In this embodiment opposing substantiallyhorizontal injection wells701 and702 are drilled using conventional directional drilling techniques. Substantiallyhorizontal production wellbores720 through729 are formed with plurality oftransverse fractures716 using any one of the techniques described above. Each of the wellbores may or may not be cased depending upon the condition of thereservoir712. As those of ordinary skill in the art will appreciate, the exact number of wellbores in the pattern can vary depending upon the conditions of the reservoir.
• Front fluid is injected into thereservoir712 through a plurality of injection ports formed alongtubing760 and762 disposed in opposing substantially horizontal injection wellbore701 and702, respectively. In this embodiment the fluid front moves away from existing well700. Accordingly, the transverse fractures closest to existing well700 are the first to be sealed. Hydrocarbons are swept into the remaining transverse fractures and recovered up the existing well through annuli formed in each of the substantiallyhorizontal production wellbores720 through729. As the flood front propagates outward and the ratio of flood fluid and the hydrocarbon production increases beyond an acceptable level additional transverse fractures are sealed successively outward until all of the transverse fractures in the substantiallyhorizontal production wellbores720 through729 are sealed. As with all the other embodiments, a flood fluid monitoring device may be disposed in each of the substantiallyhorizontal production wellbores720 through729.
• Turning toFIG. 8, yet another embodiment of the method of increasing hydrocarbon production in accordance with the present invention is illustrated. In this embodiment a pair of opposing substantiallyhorizontal injection wellbores801 and802 are formed from existing well800 inreservoir812. Furthermore, a pair of opposing substantiallyhorizontal production wellbores803 and804 are formed from existingwellbore800. Substantiallyhorizontal production wellbore803 has a plurality oflaterals805 formed therefrom. Substantially horizontal production wellbore804 similarly has a plurality ofhorizontal laterals806 formed thereof. Each of the plurality oflaterals805 and806 has a plurality of transverse fractures formed along their length using any one of the techniques described above. Thehorizontal wellbores801,802,803 and804 may or may not be cased with casing depending upon the conditions of thereservoir812. As those of ordinary skill in the art will recognize the circumstances under which thehorizontal wellbores801 through804 should be cased and whether or not tocase laterals805 and806. The transverse fractures closest to the toes of each of the plurality oflaterals805 and806 are sealed using the technique described above and plugged withdrillable plugs835 using the techniques described above. Opposingtubing860 and862 are disposed ininjection wells801 and802, respectively. Front fluid is injected intoreservoir812 through ends oftubing860 and862, which are disposed in the toe sections ofhorizontal injection wells801 and802, respectively. Under this arrangement, the fluid front830 sweeps inward. Successive transverse fractures are sealed and plugged as the front fluid ratio being produced increases beyond an acceptable level using the techniques described above. This process is repeated until all of the transverse fractures have been sealed.
• In yet another embodiment, transverse fractures916 (shown inFIG. 9B) are created sequentially during the life of the well from one end to the other, so as to deplete the zone from one end to the other (such as toe-to-heel). In one example of this alternate method, a singletransverse fracture990 is created in thetoe940 of substantiallyhorizontal wellbore910, as shown inFIG. 9A. The well910 would then be produced until the fracture produces an unacceptable level of injection fluid. Once this occurs, thetransverse fracture990 is sealed, and a secondtransverse fracture995 is created uphole and subsequently produced until it reaches an unacceptable level of injection fluid at which point a third transverse fracture (not shown) is created and so on, as shown inFIG. 9B. This embodiment is advantageous if natural fractures of high permeability streaks exist in the reservoir because the injection fluid would not be able to move through the streak and enter multiple transverse fractures at one time.
• Therefore, the present invention is well-adapted to carry out the objects and attain the ends and advantages mentioned as well as those which are inherent therein. While the invention has been depicted, described, and is defined by reference to exemplary embodiments of the invention, such a reference does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. For example, as those of ordinary skill in the art will appreciate, the exact number, size and order of the transverse fractures formed is not critical. The depicted and described embodiments of the invention are exemplary only, and are not exhaustive of the scope of the invention. Consequently, the invention is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.

Claims (44)

1.-26. (canceled)

27. A method of increasing hydrocarbon production of an existing well in a reservoir, comprising the steps of:

drilling a substantially horizontal wellbore that intersects the existing well;

forming a plurality of transverse fractures in the reservoir along the substantially horizontal wellbore;

installing a tubing in the substantially horizontal wellbore with an end of the tubing being disposed at a toe portion of the substantially horizontal wellbore, downhole of the transverse fracture farthest from the existing well;

installing a packer between the tubing and a sidewall forming the substantially horizontal wellbore uphole of the transverse fracture farthest from the existing well;

injecting a fluid into the reservoir through the end of the tubing at the toe of the substantially horizontal wellbore to force the hydrocarbons toward the plurality of transverse fractures; and

draining the hydrocarbons into the plurality of transverse fractures.

28. The method ofclaim 27 further comprising the step of squeezing a sealant into the transverse fracture farthest from the existing well to divert non-hydrocarbon fluids away from the substantially horizontal wellbore.

29. The method ofclaim 27 further comprising the step of squeezing a sealant into the transverse fracture adjacent to the one farthest from the existing well to divert the injection fluid away from the wellbore to increase the reservoir coverage and pumping the injection fluid into the farthest transverse fracture.

30. A method of increasing hydrocarbon production of an existing well from a reservoir infiltrated with a non-hydrocarbon fluid, comprising the steps of:

(a) drilling a first substantially horizontal wellbore that intersects the existing well;

(b) forming a plurality of transverse fractures in the reservoir along the first substantially horizontal wellbore;

(c) drilling a second substantially horizontal wellbore that intersects the existing well;

(d) forming at least one transverse fracture in the reservoir along the second substantially horizontal wellbore;

(e) sealing the at least one transverse fracture formed along the second substantially horizontal wellbore; and

(f) draining the hydrocarbons into the plurality of transverse fractures formed along the first substantially horizontal wellbore.

31. The method ofclaim 30 further comprising the step of injecting a fluid into the reservoir through a toe portion of the second substantially horizontal wellbore to sweep the hydrocarbons toward the plurality of transverse fractures formed along the first horizontal wellbore.

32. The method ofclaim 30 further comprising the step of lining the first and second substantially horizontal wellbores with a casing string.

33. The method ofclaim 32 wherein the casing string is cemented to sidewalls of the first and second substantially horizontal wellbores.

34. The method ofclaim 30 wherein the transverse fractures in steps (b) and (d) are formed using a hydra jetting tool.

35. The method ofclaim 34 wherein the hydra jetting tool forms each fracture one at a time.

36. The method ofclaim 35 wherein the hydra jetting tool forms transverses fracture in the first and second substantially horizontal wellbores by: (i) positioning the hydra jetting tool in the substantially horizontal wellbore being fractured at the location where the transverse fracture is to be formed; (ii) perforating the reservoir at the location where the transverse fracture is to be formed; and (iii) injecting a fracture fluid into the perforation at sufficient pressure to form a transverse fracture along the perforation.

37. The method ofclaim 30 wherein the plurality of transverse fractures in step (b) are formed by staged fracturing.

38. The method ofclaim 37 wherein the staged fracturing is performed by: (i) detonating a charge in the first substantially horizontal wellbore at the location where a transverse fracture is to be formed so as to form a perforation in the reservoir at that location; (ii) pumping a fracture fluid into the perforation at sufficient pressure to propagate the transverse fracture; (iii) installing a plug in the first substantially horizontal wellbore uphole of the transverse fracture; (iv) repeating steps (i) through (iii) until the desired number of transverse fractures have been formed; and (v) removing the plugs following the completion of step (iv).

39. The method ofclaim 30 wherein the plurality of transverse fractures in step (b) are formed using a limited entry perforation and fracture technique.

40. The method ofclaim 39 wherein the limited entry perforation and fracture technique is performed by: (i) lining the first substantially horizontal wellbore with a casing string having a plurality of sets of predrilled holes arranged along its length; and (ii) pumping a fracturing fluid through the plurality of sets of predrilled holes in the casing string at sufficient pressure to fracture the reservoir at the locations of the sets of predrilled holes.

41. The method ofclaim 30 wherein the plurality of transverse fractures in step (b) are formed by: (i) installing a tool having a plurality of hydra jets formed along its length into the first substantially horizontal wellbore; and (ii) pumping fluid through the plurality of hydra jets simultaneously at one or more pressures sufficient to first perforate and then fracture the reservoir at the locations of the hydra jets.

42. The method ofclaim 30 wherein step (e) is performed by pumping a sealant into the at least one transverse fracture that intersects the second substantially horizontal wellbore, wherein the sealant comprises a material selected from the group consisting of a cement, a linear polymer mixture, a linear polymer mixture with cross-linker, an in-situ polymerized monomer mixture, a resin based fluid, an epoxy-based fluid, and a magnesium based slurry.

43. The method ofclaim 42 wherein the sealant comprises H₂Zero™.

44. The method ofclaim 30 further comprising the step of installing a plug uphole of the at least one sealed transverse fracture.

45. The method ofclaim 30 further comprising the steps of installing a tubing in the second substantially horizontal wellbore with an end of the tubing being disposed at a toe portion of the second substantially horizontal wellbore, which is downhole of the at least one sealed transverse fracture; and installing a packer between the tubing and a sidewall forming the second substantially horizontal wellbore uphole of the at least one sealed transverse fracture.

46. The method ofclaim 45 further comprising the step of injecting a fluid into the reservoir through the end of the tubing at the toe of the second substantially horizontal wellbore to sweep the hydrocarbons toward the plurality of transverse fractures formed along the first substantially horizontal wellbore.

47. The method ofclaim 30 further comprising the step of installing a device for monitoring the amount of infiltration of the non-hydrocarbon fluid into the hydrocarbons being drained into the plurality of transverse fractures formed along the first substantially horizontal wellbore.

48. A method of increasing the hydrocarbon production of an existing well formed in a reservoir, comprising the steps of:

drilling a pair of oppositely disposed substantially horizontal injection wellbores that intersect the existing well;

drilling a plurality of substantially horizontal producing wellbores that intersect the existing well and are disposed between the injection wellbores;

forming a plurality of transverse fractures in the reservoir along each of the plurality of substantially horizontal producing wellbores;

injecting a fluid into the reservoir from the pair of oppositely disposed substantially horizontal injection wellbores; and

draining the hydrocarbons into the plurality of transverse fractures formed along the plurality of substantially horizontal producing wellbores.

49. The method ofclaim 48 wherein each of the oppositely disposed substantially horizontal injection wellbores has a multi-port tubing disposed therein through which the fluid is injected into the reservoir.

50. The method ofclaim 49 wherein the ports of each tubing are spaced substantially along the lengths of each oppositely disposed substantially horizontal injection wellbore.

51. The method ofclaim 48 wherein the hydrocarbons are swept toward the existing well.

52. The method ofclaim 51 further comprising the step of sealing one transverse fracture in each of the plurality of substantially horizontal producing wellbores, which is farthest from the existing well.

53. The method ofclaim 52 further comprising the step of sealing the next transverse fracture in each of the plurality of substantially horizontal producing wellbores, which is second farthest from the existing well.

54. The method ofclaim 53 further comprising the step of repeating the step of sealing the transverse fracture next closest to the existing well for each of the plurality of substantially horizontal producing wellbores until all of the transverse fractures have been sealed.

55. The method ofclaim 50 wherein the hydrocarbons are swept away from the existing well.

56. The method ofclaim 55 further comprising the step of sealing one transverse fracture in each of the plurality of substantially horizontal producing wellbores, which is closest to the existing well.

57. The method ofclaim 56 further comprising the step of sealing the next transverse fracture in each of the plurality of substantially horizontal producing wellbores, which is second closest to the existing well.

58. The method ofclaim 57 further comprising the step of repeating the step of sealing the transverse fracture next farthest from the existing well for each of the plurality of substantially horizontal producing wellbores until all of the transverse fractures have been sealed.

59. A method of increasing hydrocarbon production of an existing well formed in a reservoir, comprising the steps of:

drilling a pair of oppositely disposed substantially horizontal injection wellbores that intersect the existing well;

drilling a pair of oppositely disposed substantially horizontal producing wellbores that intersect the existing well and are disposed between the substantially horizontal injection wellbores, wherein each substantially horizontal producing wellbore is formed with a plurality of laterals;

forming a plurality of transverse fractures in the reservoir along each of the plurality of laterals;

injecting a fluid into the reservoir from the pair of oppositely disposed substantially horizontal injection wellbores; and

draining the hydrocarbons into the plurality of transverse fractures formed along the plurality of laterals.

60. The method ofclaim 59 wherein each of the oppositely disposed substantially horizontal injection wellbores has a tubing disposed therein through which the fluid is injected into the reservoir.

61. The method ofclaim 59 wherein the laterals are formed generally parallel to the oppositely disposed substantially horizontal injection wellbores and generally perpendicular to the oppositely disposed substantially horizontal production wellbores.

62. The method ofclaim 61 wherein the hydrocarbons are swept away from ends of the laterals farthest from the oppositely disposed substantially horizontal producing wellbores toward ends of the laterals that intersect the oppositely disposed substantially horizontal producing wellbores.

63. The method ofclaim 62 further comprising the step of sealing one transverse fracture in each of the plurality of laterals, which is farthest from the nearest substantially horizontal producing wellbore.

64. The method ofclaim 63 further comprising the step of sealing the next transverse fracture in each of the plurality of laterals, which is second farthest from the nearest substantially horizontal producing wellbore.

65. The method ofclaim 64 further comprising the step of repeating the step of sealing the transverse fracture next closest to the nearest substantially horizontal producing wellbore until all of the transverse fractures have been sealed.

66. (canceled)

67. A method of increasing hydrocarbon production of an existing well, comprising the steps of:

forming a substantially horizontal wellbore having a toe portion and a heel portion that is disposed opposite to the toe portion with the heel portion intersecting the existing well;

forming a transverse fracture at the toe section of the substantially horizontal wellbore; and

producing hydrocarbons from the well.

68. The method ofclaim 67 further comprising the steps of:

monitoring the amount of non-hydrocarbon fluid that has infiltrated the hydrocarbons being produced;

sealing the transverse fracture when an unacceptable level of injection fluid is produced;

forming a second transverse fracture uphole of the toe fracture; and

producing hydrocarbons from the second transverse fracture.

69. The method ofclaim 68 further comprising the steps of:

repeating the monitoring step;

sealing the second transverse fracture when an unacceptable level of injection fluid is produced; and

creating an additional transverse fracture uphole from the second transverse fracture from which additional hydrocarbons can be produced.

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