CA3063931A1 - Process for producing hydrocarbons from a subterranean hydrocarbon-bearing reservoir - Google Patents

Abstract

A process for producing hydrocarbons from a subterranean hydrocarbon-bearing reservoir includes injecting a fluid into the reservoir through a plurality of laterals of a multi-lateral injection well in fluid communication with the reservoir, to displace the hydrocarbons in the reservoir toward a production well prior to a fluid breakthrough at the production well, producing a portion of the hydrocarbons to surface through the production well, and monitoring for breakthrough of the fluid to the production well. After the breakthrough is detected, the process may include controlling injection of the fluid such that injection of the fluid in a lateral of the plurality of laterals of the multi-lateral injection well is controlled separately of others of the laterals of the plurality of laterals, and continuing production of the hydrocarbons through the production well and/or controlling a lateral of the production well where breakthrough is observed.

Description

PROCESS FOR PRODUCING HYDROCARBONS FROM A SUBTERRANEAN
HYDROCARBON-BEARING RESERVOIR
Technical Field [0001] The present invention relates to the production of hydrocarbons from a subterranean hydrocarbon-bearing reservoir utilizing fluid injection processes.
Background

[0002] Extensive deposits of hydrocarbons exist around the world.
Reservoirs of such deposits may be referred to as reservoirs of light oil, medium oil, heavy oil, extra-heavy oil, bitumen, or oil sands, and include large oil deposits in Alberta, Canada. It is common practice to segregate petroleum substances into categories that may be based on oil characteristics, for example, viscosity, density, American Petroleum Institute gravity ( API), or a combination thereof. For example, light oil may be defined as having an API 31, medium oil as having an API 22 and < 31, heavy oil as having an API 10 and < 22 and extra-heavy oil as having an API 10 (see Santos, R. G., et al. Braz. J.
Chem. Eng. Vol. 31, No. 03, pp. 571-590). Although these terms are in common use, references to different types of oil represent categories of convenience, and there is a continuum of properties between light oil, medium oil, heavy oil, extra-heavy oil, and bitumen. Accordingly, references to such types of oil herein include the continuum of such substances, and do not imply the existence of some fixed and universally recognized boundary between the substances.

[0003] Not all reservoirs are capable of producing oil through standard production techniques. These reservoirs may have highly viscous hydrocarbons, have one or more of low reservoir permeability, low drive energy, reservoir features such as thief zones, reservoir facies (e.g., shale breccia, heterogeneity), or a combination thereof, that do not allow for production at commercially relevant rates. For such reservoirs, various recovery techniques may be utilized to mobilize the hydrocarbons and produce the mobilized hydrocarbons from wells drilled in the reservoirs.

[0004] Oil recovery from under-pressured zones or zones that include unfavourable mobility ratios of water to oil are particularly challenging.
Standard production mechanisms such as primary recovery, water flooding, polymer flooding, gas flooding and thermal Enhanced Oil Recovery (EOR) schemes may be feasible for some reservoirs but come with their own challenges and risks.

[0005] In any recovery process, the production rate and oil recovery are controlled by key reservoir features including permeability, porosity, oil saturation, pay thickness, a pay zone is a reservoir volume having hydrocarbons that can be recovered economically, and relative permeability effects.
Furthermore, key factors controlling exploitation include pay thickness, reservoir volume (areal extent), stress state, reservoir pressure, well completion processes and accessibility by vertical or horizontal wells. Understanding of the reservoir may be improved by drilling stratigraphic wells, cutting core, running petrophysical logs, acquiring seismic data, and conducting detailed lab studies.
However, reservoir characterization does not change the rock properties of a reservoir. Different production mechanisms may result in differing oil recovery.
Thus the recovery process determines the production capability of a reservoir and its economic viability.

[0006] Improvements in oil production utilizing fluid displacement processes are desirable.
Summary

[0007] According to an aspect of an embodiment, a process for producing hydrocarbons from a subterranean hydrocarbon-bearing reservoir is provided.
The process includes injecting a fluid into the reservoir through a plurality of laterals of a multi-lateral injection well in fluid communication with the reservoir, to displace the hydrocarbons in the reservoir toward a production well prior to fluid breakthrough at the production well, producing a portion of the hydrocarbons to surface through the production well, and monitoring for breakthrough of the fluid to the production well. Both before and after breakthrough, the process may involve controlling injection of the fluid such that injection of the fluid in a lateral of the plurality of laterals of the multi-lateral injection well is controlled separately of others of the laterals of the plurality of laterals, and continuing production of the hydrocarbons through the production well.

[0008] The process may include monitoring well performance, Voidage Replacement Ratio (VRR) and flood conformance (sweep efficiency) prior to and after breakthrough. Voidage replacement ratio is the ratio of the volume of injected displacement fluid over the volume of the total produced fluid, which is the sum of swept hydrocarbon and displacement fluid, at reservoir conditions.
Brief Description of the Drawings

[0009] Embodiments of the present invention will be described, by way of example, with reference to the drawings and to the following description, in which:

[0010] FIG. 1 is a flowchart showing a process for producing hydrocarbons from a subterranean hydrocarbon-bearing reservoir according to an embodiment;

[0011] FIG. 2A is a schematic end view illustrating locations of laterals of an injection well and laterals of a production well in accordance with one example;

[0012] FIG. 2B is a schematic top view of the injection well laterals and production well laterals of FIG. 2A;

[0013] FIG. 3A is a schematic end view illustrating locations of laterals of an injection well and laterals of a production well in accordance with another example;

[0014] FIG. 3B is a schematic top view of the injection well laterals and production well laterals of FIG. 3A;

[0015] FIG. 4A is a schematic end view illustrating locations of laterals of an injection well and laterals of a production well in accordance with another example;

[0016] FIG. 4B is a schematic top view of the injection well laterals and production well laterals of FIG. 4A;

[0017] FIG. 5 through FIG. 7 are schematic end views illustrating locations of laterals of an injection well and laterals of a production well in accordance with further examples of the present application;

[0018] FIG. 8A is a schematic end view illustrating locations of injection well laterals and production well laterals that belong to a single well in accordance with another example;

[0019] FIG. 8B is a schematic top view of the injection well laterals and production well laterals of FIG. 8A;

[0020] FIG. 9 and FIG. 10 are schematic end views illustrating locations of laterals of an injection well and laterals of a production well in accordance with further examples of the present application;

[0021] FIG. 11 through FIG. 13 are schematic top views of injection well laterals and production well laterals in different configurations.
Detailed Description

[0022] The present application is directed to a process for producing hydrocarbons from a subterranean hydrocarbon-bearing reservoir in which fluid is injected into a reservoir utilizing a plurality of laterals of a multi-lateral injection well in fluid communication with the reservoir, for fluid displacement of the hydrocarbons in the reservoir to a production well. The injection well laterals are controlled and injection through the laterals may be changed over time to result in improved conformance or sweep efficiency. In particular, individual laterals of the multilateral injection well may be controlled separately such that fluid injection is changed or even discontinued from one or more of the laterals in response to detecting breakthrough of the displacement fluid from that lateral or laterals. Displacement fluid injection may be continued from other laterals.
Such configurations enable increased oil production and recovery via the controlled fluid displacement through unswept portions of the reservoir.

[0023] For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.
Numerous details are set forth to provide an understanding of the examples described herein. The examples may be practiced without these details. In other instances, well-known methods, procedures, and components are not described in detail to avoid obscuring the examples described. The description is not to be considered as limited to the scope of the examples described herein.

[0024] The disclosure generally relates to a process for producing hydrocarbons from a subterranean hydrocarbon-bearing reservoir. The process includes injecting a fluid into the reservoir through a plurality of laterals of a multi-lateral injection well in fluid communication with the reservoir, to displace the hydrocarbons in the reservoir toward a production well prior to a fluid breakthrough at the production well, producing a portion of the hydrocarbons to surface through the production well, and monitoring for breakthrough of the fluid to the production well. Before and after breakthrough is detected, the process may include controlling injection of the fluid such that injection of the fluid in a lateral of the plurality of laterals of the multi-lateral injection well is controlled separately of others of the laterals of the plurality of laterals, and continuing production of the hydrocarbons through the production well.

[0025] The processes are aimed at oil production and recovery through controlled fluid displacement through unswept portions of the reservoir.
Mobility ratio is related to the rate at which water preferentially flows over oil due to the ratio of viscosity and relative permeability to each phase. The purpose of changing displacement fluids or introducing additives is to improve sweep of hydrocarbon through the rock into the production well by enhancing the mobility ratio to oil flow. Sweep can be improved by increasing viscosity of the displacement fluid or decreasing viscosity of the hydrocarbon fluid through chemical additives and/or temperature. Sweep can also be improved by reducing the interfacial tension between the aqueous and hydrocarbon phases through chemical additives such as alkali or surfactants, thereby enhancing the relative permeability to oil.

[0026] The controlled fluid displacement process utilizes difference in densities between hydrocarbons in a subterranean hydrocarbon-bearing reservoir and aqueous or hydrocarbon based displacement fluids injected into a reservoir at a plurality of locations through a multi-lateral injection well.

[0027] The process involves placing a multi-lateral injection well in, above, or below a pay zone. For example, in the case in which an underlying water zone exists, multilateral injectors may be placed in the water zone, below the pay zone. A production well is located within the pay zone to receive fluids displaced by the displacement fluid injected via the multi-lateral injection well.
Injection may be controlled to separately control the laterals of the multi-lateral injection well. Well stimulation by, for example, fracturing to increase reservoir access are also viable options for the recovery process.

[0028] Displacement fluid injection may begin at first oil production, or may be implemented later in the production time. As an example, several multilateral wells may be drilled as production wells and, a later time, one or multiple wells may be converted to injectors. Displacement fluid injection may be continuous or implemented in batch sequences (cycles). Oil production may occur continuously.
However the process does not require both injection and production to occur continuously or simultaneously. As displacement fluid injection occurs, the displacement fluid from the injection well displaces the hydrocarbons in the formation. A fluid zone, such as a water zone may expand or may be formed as injection is carried out. Different displacement fluids may be used in the process and may be aqueous based or may be hydrocarbon based displacement fluids.
The selection of displacement fluids depends on the nature of the reservoir and the displacement fluid may be changed over time. For example, after a period of injecting a first displacement fluid, a different displacement fluid may be injected.
In addition, a foam or other chemical additives may be utilized.

[0029] The drive mechanisms of the process vary in magnitude depending on the nature of the reservoir and operating conditions for the process.
Displacement fluid injection pressures close to the reservoir pressure result in the displacement of hydrocarbons in the reservoir, toward the production well.

The displacement fluid injection pressure may be at or above the reservoir pressure. Lower injection pressures may result in longer times until breakthrough of the displacement fluid into the production well and greater efficiency at sweeping the hydrocarbons to the production well. Higher injection pressures may increase the drive mechanism, increasing production rates but decreasing sweep efficiency and time to breakthrough of the displacement fluid into the production well. Optionally, the injection pressures may be at or above a fracture pressure of the reservoir.

[0030] The injection pressure through the multi-lateral injection well may be controlled and may be changed over time such that the injection pressures may be changed after injecting displacement fluid for a period of time.
Pressures in individual laterals of the multi-lateral injection well may be controlled utilizing flow control devices or other suitable devices. Pressure at the production well may be monitored and controlled by the flow rate in the production well, the displacement fluid flow rates and pressure, which may be separately controlled in each of the laterals of the multi-lateral injection well. Laterals of the multi-lateral injection well may be equipped with downhole heaters within or around the laterals to improve or enhance performance. Each lateral may be equipped with a different heater and each heater may optionally be separately controllable.

[0031] Eventually, a path forms through which the displacement fluid enters the production well, referred to herein as displacement fluid breakthrough.
After displacement fluid breakthrough occurs, hydrocarbon production rates are limited as displacement fluid production increases.

[0032] After displacement fluid breakthrough occurs at the production well, the injection of the displacement fluid through the laterals may be separately controlled such that a lateral of the multi-lateral injection well is controlled separately of the other laterals. The injection of displacement fluid may be controlled by re-completing the lateral of the multi-lateral injection well, isolating the lateral, installing a flow control device or devices, installing one or multiple tubing string to control fluid injection along the length of the lateral, re-drilling a section of the lateral, drilling or opening a sidetrack of the lateral, or any combination of these techniques.

[0033] The displacement fluid injection through one of the laterals may be controlled separately from the displacement fluid injection through other laterals by discontinuing injection of the displacement fluid through the lateral from which the displacement fluid that formed the path to the production well is injected. Injection of displacement fluid through other laterals, however, may continue. Thus, the path that forms, through which the displacement fluid enters the production well, may be controlled to discontinue breakthrough, improving the sweep efficiency of the hydrocarbons toward the production well.
Eventually, displacement fluid breakthrough occurs from other laterals of the multi-lateral injection well, but not until further oil production is realized.

[0034] The production well is typically a multilateral well but may optionally be a single lateral production well. The injection wells and each production well may therefore be a multi-lateral well, for example, including 24 or more laterals each. Each lateral of the multi-lateral production well may also be separately controlled such that production from a lateral of the multi-lateral production well is controlled separately of the other laterals of the multi-lateral production well.

[0035] Adjacent laterals of the multi-lateral injection well may be spaced apart horizontally by about 25 meters to about 200 meters. For example, adjacent laterals of the multi-lateral injection well may be spaced apart by about 50 meters. Vertical spacing between adjacent laterals of the multi-lateral injection well may be spaced apart by about 5 meters to about 25 meters. The laterals of the multi-lateral injection well may be spaced horizontally from the production well by about 25 meters to about 200 meters. For example, the laterals of the multi-lateral injection well may be spaced from the production well by about 50 meters. In examples in which the production well is a multi-lateral production well, laterals of the multi-lateral production well may also be spaced apart by about 25 meters to about 200 meters, for example, by about 50 meters. Vertical spacing between adjacent laterals of the multi-lateral production well may also be spaced apart by about 5 meters to about 25 meters.

[0036] A process for producing hydrocarbons from a subterranean hydrocarbon-bearing reservoir is shown in FIG. 1. The process may include additional or fewer elements than shown and described. The process is carried out utilizing a multilateral injection well to a multilateral production well, or a multi-lateral injection well to a horizontal production well that extend into a reservoir. The process shown in FIG. 1 may begin after a primary production method is carried out such that the process illustrated in FIG. 1 is part of a hydrocarbon production method. The primary production may include any process in which a production well is drilled and completed and production is started. The completion of the production well may include the addition of liners, perforating, fracturing, acidizing, or other processes. For example, the process described with reference to FIG. 1 may begin up to 10 years after an earlier, or primary production process is initiated. The process may begin after some percentage or quantity of hydrocarbons are recovered, such as 10% of the hydrocarbons from the formation, after a given period of time, such as 4 years or less, or based on an economic criteria.

=

[0037] The process may begin after recovery of hydrocarbons, for example, utilizing a conventional hydrocarbon recovery process. Such a conventional process may be discontinued when the process becomes uneconomical or less economical. The injection and/or production wells may optionally be recompleted. Additional injection well laterals may be drilled and completed after production. Additional production well laterals may also be drilled and completed. The process illustrated in FIG. 1 and described herein may then be carried out to recover residual hydrocarbons. For example, the process illustrated in FIG. 1 may be carried out utilizing wells at which hydrocarbon recovery operations were previously discontinued because production became uneconomical utilizing conventional methods.

[0038] A displacement fluid is injected into the reservoir through the injection well at 102. The displacement fluid may be aqueous or hydrocarbon based liquid. For example, the displacement fluid may be water, optionally with one or more additives, and contaminants. Hot water may be utilized as the displacement fluid to reduce oil viscosity and improve mobility compared to that utilizing unheated water. Additives such as alkali, polymers, surfactants, brines and/or other additives may also be utilized to enhance displacement and/or improve mobility. The injection pressure of the displacement fluid is suitable to provide a differential pressure between the laterals of the multi-lateral injection well and the production well, to facilitate sweeping the hydrocarbons toward the production well prior to displacement fluid breakthrough at the production well.
The injection of displacement fluid is thus controlled.

[0039] The rate of oil recovery and a time to displacement fluid breakthrough may be controlled by controlling the displacement fluid injection pressure. The differential pressure between the laterals of the multi-lateral injection well and the production well may be controlled to facilitate optimal sweep of hydrocarbons to the production well. For example, the production well pressure may be increased to reduce the differential pressure with an underlying or overlying thief zone. Thief zones may include, for example, top water zones, bottom water zones, and gas caps (including top gas zones that have been produced, and therefore have reduced pressure).

[0040] A portion of the hydrocarbons are produced to surface through the production well at 104.

[0041] Production of the hydrocarbons through the production well continues as the production well is monitored for displacement fluid breakthrough at 106. In addition, reservoir conformance, including sweep efficiency, and VRR are monitored. Monitoring may include displacement fluid to oil ratio, hydrocarbon production rate, cumulative hydrocarbon produced, displacement fluid injection rate, cumulative displacement fluid injected, displacement fluid production rate, cumulative displacement fluid produced, injection pressure, production pressure, injection temperature, production temperature, or a combination thereof. Alternatively, or in addition, monitoring may include reservoir surveillance data obtained from at least one of a seismic survey, an observation well, a production log, an injection well-production well communication test, shutting-in one or more laterals of the injection well to observe pressure build-up, shutting in the production well to observe pressure build-up, or a combination thereof.

[0042] In response to detecting displacement fluid breakthrough at 108, the process continues at 110. The lateral from which the displacement fluid that formed the path to the production well was injected, is identified to control the injection from this lateral. The lateral from which the displacement fluid that formed the path to the production well is injected, may be controlled separately of the other laterals of the multi-lateral injection well. For example, the injection of displacement fluid may be controlled by re-completing the lateral of the multi-lateral injection well, isolating the lateral, installing a flow control device or devices, installing one or multiple tubing strings to control fluid injection along the length of the lateral, re-drilling a section of the lateral, drilling or opening a sidetrack of the lateral, or any combination of these techniques.

[0043] Isolating the lateral may be carried out to discontinue injection of the displacement fluid through the lateral from which the displacement fluid that formed the path to the production well, is injected. Injection of displacement fluid through other laterals, however, is continued.

[0044] In the case in which the production well is a multi-lateral production well, production from laterals of the multi-lateral production well may also be controlled at 110, such that production from one or more of the laterals of the multi-lateral production well may be controlled separately of the others of the laterals of the multi-lateral production well to increase sweep efficiency.

[0045] Hydrocarbon production continues at 112, after displacement fluid breakthrough. For example, after isolating a lateral of the horizontal multi-lateral injection well and discontinuing injection from that lateral from which the displacement fluid breakthrough was detected, the process may continue at 102.

The process may therefore continue with continued displacement fluid injection through the remaining laterals. Eventually, displacement fluid breakthrough occurs from a further lateral of the multi-lateral injection well and the further lateral may then be isolated as the process continues.

[0046] Examples of locations of laterals of an injection well and laterals of a production well are illustrated in FIG. 2 through FIG. 10. These configurations may be categorized as a bottoms-up flood, lateral flood, and line drive. FIG.

and FIG. 2B, and FIG. 5 illustrate bottoms-up flood examples. FIG. 3A and FIG.

3B, FIG. 8A and FIG. 8B, FIG. 9, and FIG. 10 illustrate lateral flood examples in which clusters of injection laterals sweep oil towards clusters of producing laterals. FIG. 6 illustrates a bottoms-up/lateral flood hybrid example. FIG.
4A and FIG. 4B illustrate a line drive example in which injection laterals are staggered between production laterals. FIG. 7 illustrates an example that does not fit any of the above categories because this is a top-down flood configuration that is implemented with a displacement fluid, such as hot water or solvent, of a lower density than the reservoir oil.

[0047] In the examples shown in the figures and described herein, different configurations of injection wells and production wells are illustrated. The method and the configurations may be generally applicable in reservoirs having a permeability of about 1 millidarcy or greater. The specific configuration utilized may be dependent on reservoir heterogeneity, including spatial variations of reservoir permeability in the x, y, and z directions. The configuration employed is therefore dependent on the reservoir and is utilized to reduce the chance of early breakthrough of displacement fluid, for example, along a high permeability path by comparison to other directions or paths within the reservoir, and to mitigate the effect when breakthrough occurs.

[0048] An illustration of locations of laterals of an injection well and laterals of a production well in a formation, in accordance with one example, is shown in FIG. 2A and FIG. 28. FIG. 2A shows an end view and FIG. 28 shows a top view of four injection well laterals 202 and four production well laterals 204. In the example of FIG. 2A and FIG. 2B, the injection well laterals 202 are disposed in a water zone 206 below a hydrocarbon-bearing pay zone 208, i.e., below a water level of the water zone 206 that is below the hydrocarbon-bearing pay zone.
The four production well laterals 204 are disposed near a top of the formation, above and generally offset laterally from the injection well laterals 202. In the present example, a gas cap 210 exists above the hydrocarbon-bearing zone 208. The production well laterals 204 are disposed in the hydrocarbon-bearing pay zone 208, below the gas cap 210.

[0049] Referring again to FIG. 1 with continued reference to FIG. 2A and FIG. 2B, an aqueous or hydrocarbon displacement fluid is injected into the reservoir through the four injection well laterals 202 at 102 and a portion of the hydrocarbons are produced to surface through the production well laterals 204 at 104. As the displacement fluid is injected via the injection well laterals 202, the displacement fluid progresses out of the water zone 206, displacing the oil in the hydrocarbon-bearing zone 208. FIG. 2A and FIG. 2B illustrate a bottom-up flood to displace the hydrocarbons.

[0050] Production of the hydrocarbons through the production well continues as monitoring is carried out at 106. In response to detecting displacement fluid breakthrough at 108, the process continues at 110 and one of the injection well laterals 202 may be isolated such that the aqueous displacement fluid is no longer injected via the lateral from which the displacement fluid that formed the path to the production well is injected.
Injection of displacement fluid through other laterals, however, is continued.

Alternatively, the process may continue at 110 by installing a tubing string into one of the injector laterals to improve sweep efficiency. Alternatively, production from one or more of the producer laterals may be controlled through the installation of a flow control device, to restrict production of the displaced fluid and promote further hydrocarbon production.

[0051] Hydrocarbon production continues at 112. The process may be repeated until breakthrough of displacement fluid from further or all of the injection well laterals 202 occurs. The process may continue even after breakthrough of the displacement fluid has occurred between each of the injection and production laterals to allow for further sweep of hydrocarbon into the production well until the process becomes uneconomic to continue operation.

[0052] Another example of locations of laterals of an injection well and laterals of a production well in a formation is illustrated in FIG. 3A and FIG. 3B, in which FIG. 3A shows an end view and FIG. 3B shows a top view of four injection well laterals 302 and four production well laterals 304. In the example of FIG. 3A and FIG. 3B, the injection well laterals 302 are disposed to one side of the production well laterals 304. The injection well laterals 302 are generally disposed in a vertical stack, with each one of the injection well laterals 302 disposed at a different depth within the formation. In the present example, one of the injection well laterals 302 is disposed in a water zone 306 below a hydrocarbon-bearing pay zone 308, i.e., below a water level of the water zone 306 that is below the hydrocarbons. The remaining three injection well laterals 302 are disposed in the stack in the hydrocarbon-bearing pay zone 308. The four production well laterals 304 are disposed in the hydrocarbon-bearing pay zone 308, and are laterally spaced apart at generally regular intervals. The vertical placement of the production well laterals 304 may be optimized based on the geology of the reservoir. In the present example, a gas cap 310 exists above the hydrocarbon-bearing pay zone 308. The production well laterals 304 are disposed in the hydrocarbon-bearing pay zone 308, below the gas cap 310.

[0053] The process described above with reference to FIG. 1 may also be carried out with the injection well laterals 302 and the production well laterals 304 of FIG. 3A and FIG. 3B. As in the example described above with reference to FIG. 2A and FIG. 2B, the displacement fluid displaces the hydrocarbons toward the production well laterals 304. FIG. 3A and FIG. 3B illustrate a lateral flood to displace the hydrocarbons. The lateral flood may be advantageous in examples in which stratified geological layers with different permeabilities are present in the pay zone.

[0054] Another example of locations of locations of laterals of an injection well and laterals of a production well, which in this example, is referred to as a linedrive multi-lateral flood configuration, is illustrated in FIG. 4A and FIG. 4B, in which FIG. 4A shows an end view and FIG. 4B shows a top view of four injection well laterals 402 and four production well laterals 404. In the example of FIG.
4A and FIG. 4B, the injection well laterals 402 are interposed with the production well laterals 404. The injection well laterals 402 and the production well laterals 404 are generally at the same depth in the formation, within the hydrocarbon-bearing pay zone 408. The production well laterals 404 are generally equally spaced within the hydrocarbon-bearing pay zone 408. Similarly, the injection well laterals 402 are generally equally spaced within the hydrocarbon-bearing pay zone 408 such that an injection well lateral 402 is generally located at a midpoint between adjacent production well laterals 404. The formation in the present example also includes a water zone 406 below the hydrocarbon-bearing pay zone 408, and a gas cap 410 above the hydrocarbon-bearing zone 408.

[0055] The process described above with reference to FIG. 1 may also be carried out with the injection well laterals 402 and the production well laterals 404 of FIG. 4A and FIG. 4B. As in the example described above with reference to FIG. 2A and FIG. 2B, the displacement fluid displaces the hydrocarbons toward the production well laterals 404. FIG. 4A and FIG. 4B illustrate a line drive multi-lateral flood configuration to displace the hydrocarbons. The line drive multi-lateral flood may be advantageous for achieving effective sweep in relatively thin pay zones.

[0056] Other examples of locations of laterals of an injection well and laterals of a production well in a formation are illustrated in FIG. 5 through FIG.
10. FIG. 5 shows an end view of four injection well laterals 502 and four production well laterals 504 in a formation that varies in depth in accordance with one example. The injection well laterals 502 are generally laterally spaced apart at the same depth. The production well laterals 504 are also generally laterally spaced apart at the same depth. The injection well laterals 502, however, are disposed in a portion of the formation that is at a greater depth than the portion of the formation at which the production well laterals 504 are disposed. Thus, the injection well laterals 502 are disposed at a much greater depth than the production well laterals 504 and the group of injection well laterals 502 is laterally spaced from the group of production well laterals 504. In the present example, no water zone or gas cap is shown. A water zone or gas cap may be present, however.

[0057] The process described above with reference to FIG. 1 may also be carried out with the injection well laterals 502 and the production well laterals 504 of FIG. 5. The displacement fluid is injected via the injection well laterals 502, displacing the oil in the hydrocarbon-bearing zone, also referred to as the pay zone 508, toward the production well laterals 504. In the case in which no water zone exists, an aqueous zone may be formed as displacement fluid is injected via the injection well laterals 502. FIG. 5 illustrates a bottoms-up flood to displace the hydrocarbons.

[0058] FIG. 6 shows an end view of four injection well laterals 602 and four production well laterals 604 in a formation that varies in depth in accordance with another example. The injection well laterals 602 are generally stacked such that each of the injection well laterals 602 is disposed at a different depth.
The production well laterals 604 are generally laterally spaced apart at the same depth. The injection well laterals 602, however, are disposed in a portion of the formation that is at a greater depth than the portion of the formation at which the production well laterals 604 are disposed. Thus, the injection well laterals 602 are all disposed at a greater depth than the production well laterals 604 and the group of injection well laterals 602 is laterally spaced from the group of production well laterals 604. In the present example, no water zone or gas cap is shown. A water zone or gas cap may be present, however.

[0059] The process described above with reference to FIG. 1 may also be carried out with the injection well laterals 602 and the production well laterals 604 of FIG. 6. The displacement fluid is injected via the injection well laterals 602, displacing the oil in the hydrocarbon-bearing or pay zone 608, toward the production well laterals 604. In the case in which no water zone exists, an aqueous zone may be formed as displacement fluid is injected via the injection well laterals 602. FIG. 6 illustrates a combination lateral flood and bottoms-up flood to displace the hydrocarbons.

[0060] Yet another example of four injection well laterals 702 and four production well laterals 704 is illustrated in FIG. 7. In the present example, the injection well laterals 704 are disposed near a top of the formation, above and generally offset laterally from the production well laterals 702. In the present example, no water zone or gas cap is shown. A water zone may be present, however.

[0061] The process described above with reference to FIG. 1 may also be carried out with the injection well laterals 702 and the production well laterals 704 of FIG. 7. The displacement fluid is injected via the injection well laterals 702, displacing the oil in the hydrocarbon-bearing or pay zone 708, toward the production well laterals 704. The displacement fluid in this example may have a lower density than the hydrocarbon present in the pay zone 708, for example, hydrocarbon-based displacement fluids such as a natural gas liquid or a condensate blend. In the case in which no water zone exists, an aqueous zone may be formed as displacement fluid is injected via the injection well laterals 702.

[0062] In the examples referred to and described above, four injection well laterals and four production well laterals are shown. Other numbers of injection well laterals and other numbers of production well laterals may be successfully implemented, however. The number of injection well laterals may differ from the number of production well laterals. In addition, the injection well laterals and the production well laterals may be drilled from different surface locations than those illustrated in FIG. 2B, FIG. 36, and FIG. 46. Alternatively, injection well laterals and the production well laterals may be completed from a same well bore.

[0063] FIG. 8A and FIG. 86 illustrate an example in which three injection well laterals 802 are utilized and two production well laterals 804 are utilized.
The injection well laterals 802 and the production well laterals 804 are laterals completed from the same well such that the injection well laterals 802 and production well laterals 804 are completions from the same well and are separately controllable for injection and production. For the purpose of this example, the injection well laterals 802 are generally stacked such that each lateral of the injection well laterals 802 is disposed at a different depth in the formation. The injection well laterals 802 are disposed horizontally between the production well laterals 804. The displacement fluid is injected via the injection well laterals 802, displacing the oil in the hydrocarbon-bearing or pay zone 808, toward the production well laterals 804.

[0064] The process described above with reference to FIG. 1 may also be carried out with the injection well laterals 802 and the production well laterals 804 of FIG. 8A and FIG. 86.

[0065] FIG. 9 illustrates a further example of injection well laterals 902 and production well laterals 904 in which the injection well laterals 902 are generally stacked such that each of the injection well laterals 902 is at a different depth in the formation, and the production well laterals 904 are generally stacked such that each of the production well laterals 904 is at a different depth in the formation. The stack of injection well laterals 902 is generally spaced from the stack of production well laterals 904. The displacement fluid is injected via the injection well laterals 902, displacing the oil in the hydrocarbon-bearing or pay zone 908, toward the production well laterals 904. The process described above with reference to FIG. 1 may also be carried out with the injection well laterals 902 and the production well laterals 904 of FIG. 9.

[0066] FIG. 10 illustrates yet a further example of injection well laterals 1002 and production well laterals 1004 in which the injection well laterals are generally stacked such that each of the injection well laterals 1002 is at a different depth in the formation, and the production well laterals 1004 are generally arranged with pairs of production well laterals 1004 stacked. The pairs are spaced apart such that each production well lateral 1004 in a stack is at a different depth in the formation. The stack of injection well laterals 1002 is generally spaced from the closest pair of production well laterals 1004. The displacement fluid is injected via the injection well laterals 1002, displacing the oil in the hydrocarbon-bearing or pay zone 1008, toward the production well laterals 1004. The process described above with reference to FIG. 1 may also be carried out with the injection well laterals 1002 and the production well laterals 1004 of FIG. 10.

[0067] Yet another example of injection well laterals 1102 and production well laterals 1104 is illustrated in the schematic top view of FIG. 11. In this example, the injection well laterals 1102 are generally perpendicular to the production well laterals 1104. The injection well laterals 1102 are spaced vertically from the production well laterals 1104.

[0068] As illustrated in the schematic top view of FIG. 12, the injection well laterals 1202 and production well laterals 1204 may extend at an angle relative to each other, such that the injection well laterals 1202 are not parallel to nor perpendicular to the production well laterals 1204. The injection well laterals 1202 are spaced vertically from the production well laterals 1204.

[0069] Yet a further example of injection well laterals 1302 and production well laterals 1304 is illustrated in the schematic top view of FIG. 13. As with the example illustrated in FIG. 12, the injection well laterals 1302 and production well laterals 1304 extend at an angle relative to each other, such that the injection well laterals 1302 are not parallel to nor perpendicular to the production well laterals 1304. The injection well laterals 1302 are spaced vertically from the production well laterals 1304.

[0070] The configurations illustrated are utilized to improve sweep efficiency compared to conventional injection and production wells. The specific configuration utilized may be dependent on several factors, including the reservoir geology, surface limitations, or a combination thereof.

[0071] In the examples described, the production well includes multiple laterals. A single production well with only one lateral may be successfully implemented, however. The production well may be a vertical, deviated, horizontal, or a multi-lateral well. The use of horizontal multi-lateral production wells is beneficial to hydrocarbon production as the laterals of the horizontal multi-lateral production well increase the effective inflow area from the reservoir during the process.

[0072] The number of injection well laterals may be limited by economics, limitations from drilling, surface limitations, or a combination thereof. The optimum number of laterals may'vary depending on geology and well economics.
The number of laterals may be determined by economics, to improve hydrocarbon production and reduce the cost of injection, drilling, completions and facility tie-ins.

[0073] In the case of consolidated (fractured or unfractured) reservoirs, multi-lateral wells may be drilled and left uncased (open-hole) and maintain stable wellbore conditions. The stability of the wellbore is dependent on the stress state of the rock, the mechanical properties of the reservoir (rock and fluid), and the conditions within the wellbore, including temperature and pressure. In some applications, cased injection wells may be utilized. Cased production wells may also be utilized depending on the wellbore conditions.
Cased injection or production wells may be utilized, for example, to improve wellbore stability, to deploy a liner or liners, inflow control devices, or any combination of wellbore completions to facilitate hydraulic flow.

[0074] Some drilling parameters may be evaluated before drilling, completion, and production in order to maintain wellbore stability and prevent compressive (wellbore break-outs) or tensile (fractures) failures in the rock.
For instance, the most common technique of controlling such drilling parameters in drilling is with the mud weight drilled in the formation (also referred to as the mud window). By running and cementing successive intermediate casing strings through different geological formations, the mud window in a given geological formation may be widened without concern of failure in up-hole formations.
Barring no changes to the formation during drilling, any well-servicing operations typically operate within a similar mud window.

[0075] Other drilling and operating parameters may be evaluated before drilling, completion, and production including drilling fluid or displacement fluid compatibility with the formation to minimize or inhibit damage to the reservoir.

[0076] During production, the primary concern with wellbore stability is in relation to wellbore breakout associated with significant reduction in flowing pressures in the open-hole laterals and corresponding stress concentrations around the wellbore. Operational strategies including carefully monitoring production rates and sand cuts may reduce significant temperature or pressure perturbations in the wellbore and inhibit wellbore failures.

[0077] A significant improvement may be realized by the use of multi-lateral injection wells in the economics of the process relative to single injection wells. The cost of drilling several laterals is much lower than the cost of drilling multiple single horizontal wells. Control of breakthrough at the production well may depend on the configuration. The injection well laterals closest to the production well may be the first to be the source of fluid breakthrough. After fluid breakthrough is detected, production of the hydrocarbons may continue.

[0078] Advantageously, hydrocarbon production utilizing the controlled fluid displacement process may be improved utilizing one or more multi-lateral injection wells for injecting a displacement fluid. After displacement fluid breakthrough is detected, injection may be controlled via various methods as described herein to facilitate continued hydrocarbon production utilizing the process.

[0079] The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. All changes that come with meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (30)

Claims

1. A process for producing hydrocarbons from a subterranean hydrocarbon-bearing reservoir, the process comprising:
injecting a fluid into the reservoir through a plurality of laterals of a multi-lateral injection well in fluid communication with the reservoir, to displace the hydrocarbons in the reservoir toward a production well prior to a fluid breakthrough at the production well;
producing a portion of the hydrocarbons to surface through the production well;
monitoring for breakthrough of the fluid to the production well, and, after the breakthrough is detected:
controlling injection of the fluid such that injection of the fluid in a lateral of the plurality of laterals of the multi-lateral injection well is controlled separately of others of the laterals of the plurality of laterals; and continuing production of the hydrocarbons through the production well.

2. The process according to claim 1, wherein controlling injection of the fluid comprises discontinuing injection of the fluid through the lateral of the plurality of laterals of the multi-lateral injection well and continuing injection of the fluid through the other laterals of the plurality of laterals.

3. The process according to claim 1, wherein controlling injection of the fluid comprises at least one of: re-completing a lateral of the multi-lateral injection well, isolating the lateral of the multi-lateral injection well, installing a flow control device, installing one or multiple tubing strings in the lateral of the multi-lateral injection well, re-drilling a section of the lateral of the multi-lateral injection well, drilling or opening a sidetrack of the lateral of the multi-lateral injection well, or a combination thereof.

4. The process according to claim 1, wherein controlling injection of the fluid comprises at least one of modifying an operating pressure, changing the fluid injected, and changing one or more additives to the fluid.

5. The process according to claim 1, comprising monitoring at least one of well performance, sweep, sweep efficiency, and Voidage Replacement Ratio (VRR), in addition to monitoring for breakthrough.

6. The process according to claim 5, wherein monitoring at least one of well performance, sweep, sweep efficiency, and Voidage Replacement Ratio (VRR), in addition to monitoring for breakthrough comprises monitoring at least one of:
a water to oil ratio, a hydrocarbon production rate, a fluid injection rate, an injection pressure, a production pressure, a production temperature, cumulative injection volumes, cumulative production volumes, concentration of a tracer element or composition of the produced fluid relative to the injected displacement fluid, and a combination thereof.

7. The process according to claim 6, wherein monitoring at least one of well performance, sweep, sweep efficiency, and Voidage Replacement Ratio (VRR), in addition to monitoring for breakthrough comprises analyzing monitoring data obtained from at least one of a seismic survey, an observation well, a production log, an injection well-production well communication test, shutting in the injection well, or a combination thereof.

8. The process according to claim 1, wherein the fluid comprises water injected as a liquid into the reservoir.

9. The process according to claim 1, wherein the fluid comprises an aqueous or hydrocarbon based liquid.

10. The process according to claim 1, comprising heating the reservoir utilizing downhole heaters in laterals of the multi-lateral injection well.

11. The process according to claim 1, wherein the production well comprises a multi-lateral production well.

12. The process according to claim 11, comprising heating the reservoir utilizing heaters in laterals of the multi-lateral production well.

13. The process according to claim 11, wherein production from laterals of the multi-lateral production well is separately controllable such that production from a lateral of laterals of the multi-lateral production well is controlled separately of others of the laterals of the multi-lateral production well.

14. The process according to claim 1 wherein injecting the fluid comprises injecting at a pressure at or above the reservoir pressure.

15. The process according to claim 1 wherein injecting the fluid comprises injecting at a temperature at or above the reservoir temperature.

16. The process according to claim 1 wherein injecting the fluid comprises injecting at a pressure above a fracture pressure of the reservoir.

17. The process according to claim 1, comprising changing the injection fluid after injecting for a period of time.

18. The process according to claim 1, comprising recovering hydrocarbons from the subterranean hydrocarbon-bearing for period of time of 10 years or less prior to injecting the fluid and producing the portion of the hydrocarbons.

19. The process according to claim 1, wherein one or more laterals of the multi-lateral injection well are located in a water zone below the hydrocarbon formation and injecting fluid comprises injecting water into the water zone.

20. The process according to claim 1, wherein injecting fluid comprises injecting to create or in.crease an aqueous level in a water zone and displace the hydrocarbons.

21. The process according to claim 1, comprising monitoring the production well prior to injecting the fluid and, in response to first production of hydrocarbons through the production well, commencing injecting the fluid.

22. The process according to claim 1, wherein a horizontal spacing between laterals of the multi-lateral injection well is about 25m to about 200m.

23. The process according to claim 1, wherein a horizontal spacing between a lateral of the plurality of the laterals of the multi-lateral injection well and a closest lateral of the production well is about 25m to about 200m.

24. The process according to claim 1, wherein a vertical spacing between laterals of the multi-lateral injection well is about 5m to about 25m.

25. The process according to claim 1, wherein a vertical spacing between laterals of the multi-lateral injection well and a closest lateral of the production well is about 5m to about 25m.

26. The process according to claim 1, wherein the production well comprises a multi-lateral production well and laterals of the multi-lateral production well extend in a first direction and laterals of the multi-lateral injection well extend in a second direction that differs from the first direction.

27. The process according to claim 26, wherein the first direction is at an angle relative to the second direction such that the laterals of the multi-lateral production well are not parallel with the laterals of the multi-lateral injection well.

28. The process according to claim 26, wherein the laterals of the multi-lateral production well are vertically spaced from laterals of the multi-lateral injection well.

29. The process according to claim 1, wherein injecting a fluid into the reservoir comprises injecting the fluid into at least a portion of the reservoir having a permeability of about 1 millidarcy or greater.

30. A process for removing fluids from a hydrocarbon reservoir utilizing a multi-lateral injection well in fluid communication with the hydrocarbon reservoir and a production well extending into the reservoir, the process comprising:
injecting an aqueous or hydrocarbon-based liquid into the reservoir through a plurality of laterals of a multi-lateral injection well to displace the fluids in the reservoir toward a production well;
recovering a portion of the fluids through the production well;
in response to detecting breakthrough of the aqueous or hydrocarbon-based liquid from a lateral of the plurality of laterals to the production well, discontinuing injecting the aqueous or hydrocarbon-based liquid through the lateral of the plurality of laterals and continuing injection of the aqueous or hydrocarbon-based liquid through the other laterals of the plurality of laterals.