Systems and Methods for Conformance Control of a Wellbore

This disclosure relates to systems and methods for conformance control of a wellbore.

Oil production with high water cut is a well-recognized problem in the oil industry and reducing water cut has become an important target for oilfield operators. High water cut not only increases the cost of oil production, but from the source, high water cut is closely related to poor conformance control and lower sweeping efficiency of an injection well, especially for a reservoir dependent on the injection water to maintain reservoir energy. There are many technologies and methods that can be used to improve sweep efficiency and reduce water channeling. From the operation cycle, it can be divided into fluid flooding and improvement treatment. Fluid flooding refers to the continuous injection of displacing fluids into the formation to displace oil (with a total injection volume typically greater than 5% of the reservoir and/or well-pattern pore volume), such as polymer flooding, surfactant/polymer flooding and foam flooding.

Through these techniques, there is an increase of viscosity of the displacing fluid for improving the mobility ratio of the displacing fluid to the oil being displaced. Improvement treatment means implementing a measure on an injection or production well to reduce water production. Technologies implementing on injection wells are called conformance control, while technologies implementing on production wells are named as water shutoff. The objective of these technologies is to change the flow path of injection water.

In an example implementation, a conformance control method includes identifying a target location of a wellbore formed from a terranean surface to at least two subterranean formations. The at least two subterranean formations include a high permeability formation having a first permeability and a low permeability formation having a second permeability that is equal or less than one-third of the first permeability. The method includes forming, with a radial jet drilling assembly, a first plurality of tunnels in the high permeability formation from the wellbore; injecting, into the high permeability formation and the low permeability formation, a chemical fluid from the wellbore through the first plurality of tunnels; expanding a sweep area of the injected chemical fluid by injecting the chemical fluid into the high permeability formation through the first plurality of tunnels; forming, with the radial jet drilling assembly, a second plurality of tunnels in the low permeability formation from the wellbore; and increasing a contact area of an injection fluid in the low permeability formation with the second plurality of tunnels.

In an aspect combinable with the example implementation, each of the first plurality of tunnels is 1-2 inches in diameter and between 100 and 700 feet in length from the wellbore.

In another aspect combinable with one, some, or all of the previous aspects, each of the second plurality of tunnels is 1-2 inches in diameter and between 100 and 700 feet in length from the wellbore.

In another aspect combinable with one, some, or all of the previous aspects, the chemical fluid includes a gel.

In another aspect combinable with one, some, or all of the previous aspects, the chemical fluid includes swellable particles.

Another aspect combinable with one, some, or all of the previous aspects includes logging the wellbore.

Another aspect combinable with one, some, or all of the previous aspects includes identifying the target location based at least in part on a log of the wellbore generated by the logging.

Another aspect combinable with one, some, or all of the previous aspects includes injecting the injection fluid into the wellbore subsequent to forming the second plurality of tunnels in the low permeability formation.

In another aspect combinable with one, some, or all of the previous aspects, the first plurality of tunnels includes between 2 and 8 tunnels.

In another aspect combinable with one, some, or all of the previous aspects, the second plurality of tunnels includes between 2 and 8 tunnels.

In another aspect combinable with one, some, or all of the previous aspects, a volume of the injected chemical fluid includes between 0.02 and 0.10 pore volume of the high permeability formation.

Another aspect combinable with one, some, or all of the previous aspects includes isolating, with a temporary zonal isolation device, the low permeability formation from the wellbore prior to injecting the chemical fluid from the wellbore through the first plurality of tunnels.

In another example implementation, a well system includes a wellbore formed from a terranean surface to a target location including at least two subterranean formations. The at least two subterranean formations include a high permeability formation having a first permeability and a low permeability formation having a second permeability that is equal or less than one-third of the first permeability. The system includes a radial jet drilling assembly configured to perform operations including forming a first plurality of tunnels in the high permeability formation from the wellbore; and subsequent to an injection of a chemical fluid, forming a second plurality of tunnels in the low permeability formation from the wellbore. The system includes a fluid injection system configured to inject the chemical fluid into the high permeability formation and the low permeability formation from the wellbore through the first plurality of tunnels. A sweep area of the injected chemical fluid is expanded by injecting the chemical fluid into the high permeability formation through the first plurality of tunnels, and a contact area of an injection fluid is increased in the low permeability formation with the second plurality of tunnels.

In an aspect combinable with the example implementation, each of the first plurality of tunnels is 1-2 inches in diameter and between 100 and 700 feet in length from the wellbore.

In another aspect combinable with one, some, or all of the previous aspects, each of the second plurality of tunnels is 1-2 inches in diameter and between 100 and 700 feet in length from the wellbore.

In another aspect combinable with one, some, or all of the previous aspects, the chemical fluid includes a gel.

In another aspect combinable with one, some, or all of the previous aspects, the chemical fluid includes swellable particles.

Another aspect combinable with one, some, or all of the previous aspects includes a logging system configured to perform injection profile logging of the wellbore.

In another aspect combinable with one, some, or all of the previous aspects, the target location is identified based at least in part on a log of the wellbore generated by the logging system.

In another aspect combinable with one, some, or all of the previous aspects, the fluid injection system is configured to inject an injection fluid into the wellbore subsequent to the formation of the second plurality of tunnels in the low permeability formation.

In another aspect combinable with one, some, or all of the previous aspects, the first plurality of tunnels includes between 2 and 8 tunnels.

In another aspect combinable with one, some, or all of the previous aspects, the second plurality of tunnels includes between 2 and 8 tunnels.

In another aspect combinable with one, some, or all of the previous aspects, a volume of the injected chemical fluid includes between 0.02 and 0.10 pore volume of the high permeability formation.

Another aspect combinable with one, some, or all of the previous aspects includes a temporary zonal isolation device positioned in the wellbore to fluidly isolate the low permeability formation from the wellbore prior to injection of the chemical fluid from the wellbore through the first plurality of tunnels.

Implementations of a systems and methods for well conformance control according to the present disclosure may include one or more of the following features. For example, implementations according to the present disclosure can treats both high and low permeability zones in a single downhole operation by increasing a water intake capacity of the low permeability zones while reducing the water intake capacity of the high permeability zones.

The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

The present disclosure describes implementations of a well system and methods for treat both high and low permeability formations that include multiple tunnels formed in the formations from a wellbore. In example implementations, systems and methods according to the present disclosure provide an integrated approach to treat high permeability and low permeability zones (i.e., subterranean formations or reservoirs) together to maximize a synergistic effect. Example implementations of a well system include a primary (for example, vertical) wellbore from which multiple tunnels are formed through both a high permeability zone that surrounds a portion of the wellbore (at a particular depth) and a low permeability zone that surrounds another portion of the wellbore (at another, different particular depth).

The tunnels can be formed, for example, by radial jet drilling and can be formed in a particular sequential order. For example, a first operation can include forming (for example, with the radial jet drilling) lateral (for instance, horizontal) tunnels from the primary wellbore in one or more high permeability zones. Subsequently, one or more chemicals can be injected from the tunnels into the one or more high permeability zones. The one or more chemicals can be allowed to migrate deeper from the one or more high permeability zones. In some aspects, the one or more chemicals include gels, swellable particles and fibers, or other materials that can be trapped in areas of high permeability zones to reduce the (relatively high) permeability

A second operation can include forming (for example, with the radial jet drilling) lateral (for instance, horizontal) tunnels from the primary wellbore in one or more low permeability zones. The one or more tunnels in the low permeability zones can increase a contact area of injected water into the low permeability zone(s) to improve a sweeping area.

As shown, the well systemaccesses a subterranean formation, and provides access to hydrocarbons located in such subterranean formation. In an example implementation of system, the systemmay be used for a drilling operation as well as a completion operation to enhance a production of hydrocarbons through a wellbore tubular string. For example, the well systemcan include a fluid injection systemthat, among other operations can inject a fluidinto the wellbore. Fluidcan represent a chemical fluid (such as a gel or gel with swellable particles) that is injected as part of a conformance control method as described here. Fluidcan also represent an injection fluid (such as water) used in a water flooding operations.

As illustrated in, an implementation of the well systemincludes a drilling assembly (or “assembly”)deployed on a terranean surface. The assemblycan generally represent a drilling assembly that can be used to form the wellboreextending from the terranean surfaceand through one or more geological formations in the Earth, as well as tunnelsand tunnelsthat are formed from the wellboreinto subterranean formationsandlocated under the terranean surface. One or more wellbore casings, such as a surface casingand intermediate casing, may be installed in at least a portion of the wellbore(for example subsequent to completion of the drilling operation or some other time).

In some embodiments, the assemblymay be deployed on a body of water rather than the terranean surface. For instance, in some embodiments, the terranean surfacemay be an ocean, gulf, sea, or any other body of water under which hydrocarbon-bearing formations may be found. In short, reference to the terranean surfaceincludes both land and water surfaces and contemplates forming and developing one or more well systemsfrom either or both locations.

Generally, as a drilling system, the assemblymay be any appropriate assembly or drilling rig used to form wellbores or boreholes in the Earth. The assemblymay use traditional techniques to form such wellbores, such as the wellboreand tunnelsand, or may use nontraditional or novel techniques. In some embodiments, the drilling assemblymay use rotary drilling equipment to form the wellboreand other, non-rotary drilling techniques (i.e., techniques that do not use a rotating drill bit) to form the tunnelsand. Rotary drilling equipment is known and may consist of a drill string and a drill bit (or bottom hole assembly that includes a drill bit). In some embodiments, the assemblymay consist of a rotary drilling rig. Rotating equipment on such a rotary drilling rig may consist of components that serve to rotate a drill bit, which in turn forms a wellbore, such as the wellbore, deeper and deeper into the ground. Rotating equipment consists of a number of components (not all shown here), which contribute to transferring power from a prime mover to the drill bit itself. The prime mover supplies power to a rotary table, or top direct drive system, which in turn supplies rotational power to the drill string. The drill string is typically attached to the drill bit (for example, as a bottom hole assembly). A swivel, which is attached to hoisting equipment, carries much, if not all of, the weight of the drill string, but may allow it to rotate freely

The non-rotary techniques can include, for example, laser drilling or radial jet drilling techniques, among others. For example, in examples in which the diameter of the wellbore(as a primary wellbore) is greater than the diameter of the tunnelsand, radial jet drilling can be an effective, environmentally friendly method to drill small-diameter horizontal tunnels (tunnelsand) from a vertical or near-vertical wellbore (wellbore) using a coiled tubing unit. Radial jet drilling can eliminate a need for a conventional bit and drilling mud by substituting such drilling features with a high-pressurized fluid that is circulated through forward and backward nozzles connected to a high pressure horse. The pressurized fluid ejected from the forward nozzles is used to erode and, therefore, “drill” a subterranean formation, while the fluid leaving the backward nozzles is used to push the nozzle forward and to widen the diameter of the formed tunnels.

In some embodiments of the well system, the wellboremay be cased with one or more casings. As illustrated, the wellboreincludes a conductor casing, which extends from the terranean surfaceshortly into the Earth. A portion of the wellboreenclosed by the conductor casingmay be a large diameter borehole. Additionally, in some embodiments, the wellboremay be offset from vertical (for example, a slant wellbore). Even further, in some embodiments, the wellboremay be a stepped wellbore, such that a portion is drilled vertically downward and then curved to a substantially horizontal wellbore portion. Additional substantially vertical and horizontal wellbore portions may be added according to, for example, the type of terranean surface, the depth of one or more target subterranean formations, the depth of one or more productive subterranean formations, or other criteria.

Downhole of the conductor casingmay be the surface casing. The surface casingmay enclose a slightly smaller borehole and protect the wellborefrom intrusion of, for example, freshwater aquifers located near the terranean surface. The wellboremay than extend vertically downward. This portion of the wellboremay be enclosed by the intermediate casing.

As shown in this example, a wellbore tubularis run into the wellbore(whether cased or not). The wellbore tubularis coupled to a bottom hole assembly (BHA). In the case of forming the wellbore(and, optionally, the tunnelsand), the wellbore tubularcan be a drill string and the BHAcan include a drill bit. In some aspects, wellbore tubularcan represent a drill string with a drill bit included in the BHAfor forming the wellborebut can be a coiled tubingwhen the BHAis a radial jet drilling unit (with no drill bit but a nozzle assembly as described herein).

In some aspects, radial set drilling can be used to form tunnelsanddue to, for example, a diameter and length of such tunnelsand. For example, tunnelsandcan approximately 1-2 inches in diameter, with lengths between, for example, 100 and 700 feet. Althoughshows two tunnelsas being formed in subterranean formationand two tunnelsas being formed in subterranean formation, there can be more (or fewer) tunnelsandformed in these respective formationsandas desired based on, for example, formation depth, thickness, geological parameters, or otherwise. In processes in which the tunnelsare formed subsequent to a chemical injection into the tunnels, a temporary zonal isolation device(for example, a temporary packer) can be installed in the wellboreto fluidly isolate the low permeability formationfrom the wellbore.

In the example of, subterranean formationrepresents a relatively high permeability formation, and subterranean formationrepresents a relatively low permeability formation. In this example, “high” and “low” permeability can be relative in that a low permeability formation, generally, is defined by a permeability value (or average permeability) of about or less than ⅓ value of a permeability value (or average permeability) of the high permeability formation. In example implementations, for instance, the relatively high permeability formationcan have a permeability of about 1000 mD while the relatively low permeability formationcan have a permeability of about 200 mD.

is another schematic diagram of the example well systemofaccording to the present disclosure. As shown in this example diagram, tunnels(two or more) extend from wellboreinto the relatively low permeability formation, while tunnels(two or more) extend from wellboreinto the relatively high permeability formation. In this example, once formed, the tunnelscan serve as injection pathways through which an injection fluidcan be circulated from the wellbore, into the tunnels, and then into the relatively high permeability formation. This injection process, in some aspects, can be completed prior to formation of the tunnelsin the relatively low permeability formation. Thus, as shown in, the wellboreis an injection well in which the injection fluid(for example, gel or swellable particles) is introduced to affect both the high permeability formationand low permeability formation.

As shown in this example, permeability decrease areasare created subsequent to the injection of the injection fluidfrom the tunnelsinto the relatively high permeability formation. As illustrated, these areascan surround the tunnelsof the relatively high permeability formation, which is made possible by the injection from tunnels(rather than, conventionally, the injection wellborealone). If no tunnelswere formed, the areaswould not be as large as compared to the illustrated example where the tunnelshave been formed (such as by radial jet drilling).

By injecting the injection fluidfrom the tunnels, the illustrated well systemcan treat both the high and low permeability formationsand, respectively, in the same operation by increasing a water intake capacity of the low permeability formationwhile reducing the water intake capacity of the high permeability formation. While the tunnelsallow for deeper migration of the injection fluid, the tunnelsformed (for example, after injection) in the low permeability formationcan effectively increase a contact area between injected water and a reservoir rock in the formation.

is another schematic diagram of a portion of the example well systemofaccording to the present disclosure. This figure shows an example radial jet drilling operation that can be used to form, for example, tunnelsand tunnels. In this example operation, subsequent to formation of the wellbore(such as by a drill bit), a deflection shoecan be installed in the wellboreand a coiled tubingcan be run in the wellbore to a particular depth (for example, in formationto form tunnels, or formationto form tunnels).

As shown in this example implementation, a high pressure hoseis coupled to the coiled tubingand ends in a jet nozzle. In this example, the jet nozzleincludes forward jetsand backward jets. A high pressure fluid is circulated through the coiled tubingand high pressure hoseand ejected as high pressure fluidfrom the forward nozzlesto erode and drill the subterranean formationto form a tunnelas shown. The high pressure fluid is also ejected as high pressure fluidfrom the backward nozzlespush the nozzleforward (i.e., into the formationaway from the wellbore) and to widen the formed tunnel

is a flowchart that shows an example methodfor treating both high and low permeability formations according to the present disclosure. In some aspects, methodcan be implemented by or with the well systemas shown in, including the high pressure fluid injection system shown in. Methodcan begin at step, which includes logging a wellbore to determine a target location of a high permeability formation and a low permeability formation. For example, once wellboreis formed (for example, with conventional rotary drilling techniques or otherwise), the BHAcan be replaced by a logging tool (or otherwise, a logging tool) and the wellborecan be logged for an injection profile. A target location can be determined by the interpretation of the log.

The target location can be a location in which heterogeneous formations—a high permeability formation and a low permeability formation—are adjacent or near each other along a depth of the injection wellbore. In some aspects, the log, therefore, determines that the low permeability formation has a permeability of about ⅓ or less of the high permeability formation.

In some aspects, subsequent to logging, an operational design for the remaining steps of methodcan be implemented, such as through a virtual model of the geophysical environment and numerical simulation. By creating the operational design based on the virtual model and numerical simulation, the improved conformance control of the formations can be achieved.