Methods of Modifying Formation Properties

FIELD OF THE INVENTION

Some embodiments described herein generally relate to systems, apparatuses, and methods for use in modifying the properties of a formation.

BACKGROUND

Reservoir quality and completion quality are two aspects of evaluating oil and gas reservoirs. Reservoir quality is a characterization of the amount and type of hydrocarbons within a reservoir, and completion quality is a characterization of the prospects for extracting the hydrocarbons within a reservoir. For example, some reservoirs may have a very high relative reservoir quality, with a large amount of valuable hydrocarbons, while other reservoirs may have a low relative reservoir quality because they have very few or low value hydrocarbon content. Some reservoirs may also have a high relative completion quality, meaning, for example, that the hydrocarbons within the reservoir may be extracted using conventional drilling and extraction techniques or other low cost drilling and extraction techniques. Some reservoirs may have a low completion quality, and unconventional mining and extraction techniques or other relatively high cost drilling and extraction techniques may be used to extract the hydrocarbons within the reservoir. Some high reservoir quality, but low completion quality, reservoirs are left untouched, because the high quality of their hydrocarbon content does not outweigh the low completion quality and high extraction costs of extracting the hydrocarbons using currently available extraction techniques.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

In one non-limiting embodiment, a method for modifying formation properties is disclosed. The method may include drilling a first wellbore into a first geologic layer. The first geologic layer may be in proximity to a second geologic layer. The method may also include removing material from the first geologic layer using a first material removal process. The properties of the first geologic layer may be changed and the properties of the second geologic layer may be changed.

In another non-limiting embodiment, a method for modifying formation properties is disclosed. The method may include drilling a wellbore into a mineral layer. The mineral layer may be in proximity to a hydrocarbon reservoir. The method may also include removing material from the mineral layer using a material removal process. The properties of the mineral layer may be changed and the properties of the hydrocarbon reservoir may be changed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 depicts a drilling rig and wellbore in a formation according to one or more embodiments disclosed herein;

FIG. 2 depicts a drilling rig and wellbore in a formation according to one or more embodiments disclosed herein;

FIG. 3 depicts a drilling rig and wellbore in a formation according to one or more embodiments disclosed herein;

FIG. 4 depicts a drilling rig and wellbore in a formation according to one or more embodiments disclosed herein;

FIG. 5 depicts a plurality of drilling rigs and wellbores in a formation according to one or more embodiments disclosed herein;

FIG. 6 depicts a plurality of drilling rigs and wellbores in a formation according to one or more embodiments disclosed herein;

FIG. 7 depicts a drilling rig and wellbore in a formation according to one or more embodiments disclosed herein;

FIG. 8 depicts a drilling rig and wellbore in a formation according to one or more embodiments disclosed herein; and

FIG. 9 depicts a method of modifying a formation according to one or more embodiments disclosed herein.

DETAILED DESCRIPTION

FIG. 1 depicts an embodiment of a drilling system 100 for aiding in the exploration of a formation 10 and the extraction of hydrocarbons, including oil and gas, from a hydrocarbon reservoir 220. The formation 10 may include one or more geologic layers. For example, the formation 10 includes a first geologic layer 210, the hydrocarbon reservoir 220, a second geologic layer that may be a shale layer 230, a mineral layer 240, and a third geologic layer 250.

The first geologic layer 210 may begin at a ground surface 12 and extend through the formation to the hydrocarbon reservoir 220 and the shale layer 230. In some embodiments, the first geologic layer may itself include one or more additional geologic layers. For example, the first geologic layer 210 may include one or more porous and/or non-porous layers between the ground surface 12 and the hydrocarbon reservoir 220 and the shale layer 230. In some embodiments, the first geologic layer 210 may include one or more additional hydrocarbon reservoirs 220.

The formation 10 may also include the hydrocarbon reservoir 220. The hydrocarbon reservoir 220 may be located within the formation 10 between the first geologic layer 210 and the shale layer 230. The hydrocarbon reservoir 220 may include oil, natural gas, or a combination of both oil and natural gas. Although depicted as a separate layer, in some embodiments the hydrocarbon reservoir 220 is incorporated into other geologic layers within the formation 10. For example, the hydrocarbon reservoir 220 may be held within a shale layer. Although depicted in FIG. 1 as having a single hydrocarbon reservoir 220, in some embodiments the formation 10 may include more than one hydrocarbon reservoir 220.

The shale layer 230 is a geologic layer of non-porous or semi-porous shale. In some embodiments, the shale layer 230 is located below the hydrocarbon reservoir 220, as shown in FIG. 1, or, in some embodiments, the shale layer 230 may be located above the hydrocarbon reservoir 220, or the formation 10 may not have a shale layer 230. As shown in FIG. 1, the shale layer 230 separates the hydrocarbon reservoir 220 from the mineral layer 240.

The mineral layer 240 may be located in proximity to or near the hydrocarbon reservoir 220. In proximity to or near the hydrocarbon reservoir 220 means that a geologic layer, in this embodiment, the mineral layer 240, is close enough to the hydrocarbon reservoir 220 that changes in the properties of the mineral layer 240 may have an effect on the properties of the hydrocarbon reservoir 220. For example, the mineral layer 240 may be adjacent or directly adjacent to the hydrocarbon reservoir 220, or the mineral layer 240 may be separated from the hydrocarbon layer 220 by hundreds or thousands of meters.

The mineral layer 240 may be below the shale layer 230 and the hydrocarbon reservoir 220 and above the third geologic layer 250. The mineral layer 240 may include deposits of one or more minerals and may include other deposits, such as, for example, water. In particular, the mineral layer 240 may include one or more of salt, limestone, dolomite, and other minerals. Although depicted as being located below the hydrocarbon reservoir 220, in some embodiments, the mineral layer 240 may be located above, or may partially or completely surround, the hydrocarbon layer 220. Although depicted as having a single mineral layer 240, in some embodiments, the formation 10 may include more than one mineral layer 240. In embodiments with more than one mineral layer 240, the mineral layers 240 may be located above, below, and/or around the hydrocarbon deposit 220.

The formation 10 may also include a third geologic layer 250. The third geologic layer 250 may begin at the mineral layer 240 and the shale layer 230 and extend through and to the bottom of the formation 10. In some embodiments, the third geologic layer 250 may itself include one or more additional geologic layers. For example, the third geologic layer 250 may include one or more porous and/or non-porous layers and one or more additional hydrocarbon reservoirs 220.

FIG. 1 also illustrates a land-based drilling system 100 positioned over a wellbore 120, and a drill string 130 for exploring formation 10. In the illustrated embodiment, the wellbore 120 is formed by drilling. Those of ordinary skill in the art given the benefit of this disclosure will appreciate that the subject matter of this disclosure also finds application in rotary drilling and directional drilling applications, and is not limited to land-based rigs.

The drill string 120 may be rotated by a rotary table which engages a kelly at the upper end of the drill string 130. The drill string 130 may be suspended from a hook, and attached to a travelling block through the kelly and a rotary swivel which permits rotation of the drill string relative to the hook. In some embodiments, the drill string 130 may be rotated using other methods, such as by using a topdrive.

The drill string 130 is suspended within the wellbore 120 and includes a downehole tool 132 as part of a bottom hole assembly at its lower, terminal, or bottom end. The downhole tool 132 may include a drill bit. The drill string 130 can also include a variety of other downhole tools 132, for example, reamers, logging while drilling tools, or other drilling tools. In some embodiments, the drill string may be a wireline tool or other tool, such as the tool associated with acidizing minerals, removing water for the formation 10, solution mining, or vibratory tools.

The wellbore 120 may include one or more sections. For example the wellbore 120 depicted in FIG. 1 includes three sections, a first or vertical section 122, a second or transition section 124 and a third or horizontal section 126. The vertical section 122 may be substantially vertical and is the section of the wellbore that penetrates through the depth of the formation 10. A conventional wellbore may have a vertical section 122 without the transition section 124 or the horizontal section 126. An unconventional wellbore may also include the transition section 124 and the horizontal section 126.

The transition section 124 of the wellbore 120 transitions the wellbore from a substantially vertical section to a substantially horizontal section. The horizontal section 126 penetrates through the mineral layer 240. Geologic layers in the formation 10, such as the mineral layer 240, may be formed in substantially horizontally arranged layers. By drilling a horizontal or substantially horizontal wellbore section, the wellbore may penetrate a greater portion of the geologic layer than if the wellbore penetrated the layer vertically.

For example, as shown in FIG. 1, the horizontal section 126 of the wellbore 120 enables the wellbore 120 to penetrate a majority of the cross section of the mineral layer 240. Although depicted as penetrating a majority of the cross section of the mineral layer 240, the horizontal section 126 of the wellbore 120 may be extended though additional horizontal drilling, such that the wellbore 120 extends through more of the mineral layer 240, for example, the wellbore 120 may extend through the entirety of or substantially the entirety of the cross section of the mineral layer 240.

Although depicted as a land-based drilling system, drilling system 100 may be an off-shore drilling system. In an offshore drilling system, the drilling system 100 may include a drilling platform or ship, and the ground surface 12 may be a sea floor.

FIG. 1 also depicts portions of a process for modifying the properties of the formation 10 and, in particular, the hydrocarbon reservoir 220. The process includes assembling a drilling system 100, including erecting the drilling rig 110, and drilling a wellbore 120 using, for example, a drill string 130. The wellbore 120 is drilled into the formation 10 to a depth near the depth of the mineral layer 240. The wellbore 120 may be drilled to include a transition section 124 that transitions the wellbore 120 from the vertical section 122 of the wellbore 120 to a horizontal section 126 of the wellbore 120. The wellbore 120 may be further extended to include the horizontal section 126 that penetrates through the cross section of the mineral layer 240.

Other drilling and formation exploration processes may also occur. For example, a wellbore casing may be installed in the wellbore, the wellbore may be enlarged, for example through reaming, formation imaging processes may take place to further understand the properties and makeup of the formation 10, and other processes may be performed.

FIG. 2 depicts portions of a process for modifying the properties of the formation 10 and, in particular, the hydrocarbon reservoir 220. The drill string 130 has been removed for clarity. In some embodiments, the drill string 130 may be located within the wellbore 120 during the portions of the process depicted in FIG. 2, while in some embodiments, the drill string 130 may be removed from the wellbore 120. In some embodiments, the mineral layer 240 may be a salt deposit layer. In FIG. 2, the wellbore 120 is drilled into the salt deposits of the mineral layer 240 and the salt may be solution mined from the mineral layer 240. The solution mining creates a void, represented by the void 242. Although depicted as a singled large void, the void 242 may represent smaller voids within the mineral layer 240 or the removal of material, such as salt, from the mineral layer 240.

In a solution mining process, one or more wellbores are drilled into the mineral layer 240. Some of the wellbores inject water into the salt deposits in the mineral layer 240 to create a salt solution or brine which can then be pumped out of the formation through, for example, the horizontal section 126 of the wellbore 120 as represented by the flow arrows 131. In some embodiments the salt deposits may be mined via underground salt mining techniques whereby the salt deposits are removed through mechanical or mechanized equipment.

By removing the salt within the mineral layer 240, the solution mining process may change the properties of the mineral layer, for example the solution mining process may change the stress regime within the mineral layer, may weaken the mineral layer 240, or may reduce the support the mineral layer 240 may provide to the rest of the formation 10, in particular the shale layer 230 and the hydrocarbon reservoir 220. As discussed in more detail below, the solution mining of the mineral layer 240 may also change the stress regime within the hydrocarbon reservoir 220.

In some embodiments, rather than or in addition to including salt deposits, the mineral layer 240 may be or include a layer or layers of limestone, dolomite, or other carbonate or deposit that can be acidized. In an acidizing process, one or more wellbores are drilled into the mineral layer 240, for example wellbore 120. Acid is injected into the formation 10 through the wellbore 120 and the acid reacts with the limestone, dolomite or other material within the mineral layer 240 of the formation 10 to clean, dissolve, and remove the minerals within the mineral layer 240.

By removing the carbonates, such as the limestone or dolomite within the mineral layer 240, the acidizing process may change the properties of the mineral layer 240, for example the acidizing process may change the stress regime within the mineral layer 240, may weaken the mineral layer 240, or may reduce the support the mineral layer 240 may provide to the rest of the formation 10, in particular the shale layer 230 and the hydrocarbon reservoir 220. As discussed in more detail below, the acidizing of the mineral layer 240 may also change the stress regime within the hydrocarbon reservoir 220.

In some embodiments, the mineral layer 240 of formation 10 may be or include water or other liquids. In such embodiments, the water may be pumped out or otherwise removed from the mineral layer 240. Removing the water may change the properties of the mineral layer 240. For example, water held within the mineral layer 240 may provide support to the mineral layer 240. By removing the water, the properties of the mineral layer 240 may be changed, for example the stress regime within the mineral layer may change such that the mineral layer 240 is weaker, or the mineral layer 240 may provide less support to the rest of the formation 10, in particular the mineral layer 240 may provide less support to the shale layer 230 and the hydrocarbon reservoir 220. As discussed in more detail below, removing water from the mineral layer 240 may also change the stress regime within the hydrocarbon reservoir 220.

In some embodiments, vibrator tools may be used within the mineral layer 240 in addition to or alternatively to one or more of removing water from the mineral later 240, acidizing the mineral layer 240, and salt mining the mineral layer 240. The vibratory tools may cause mechanical waves, such as seismic waves, to propagate through the formation 10 and in particular within the mineral layer 240 and/or the hydrocarbon reservoir 220. The mechanical waves may change the stress regime within the formation 10 by, for example, causing fractures within the formation 10, or causing one or more of the geologic layers to settle or compact and other geologic layers to stretch or expand.

Although the processes described above are discussed in the context of the mineral layer 240, in some embodiments, the processes may be carried out on one or more of the portions of the formation 10 that are not the mineral layer 240, for example, the first geologic layer 210, the shale layer 230, or the third geologic layer 250.

The processes described above, including salt mining, acidizing, water removal, and vibration, collectively referred to as removal processes, may be performed before, during, or after removal of hydrocarbons from the hydrocarbon reservoir 220. In some embodiments, removing oil from the hydrocarbon reservoir 220 with a low completion quality may be expensive or very technically difficult; therefore, a well operator may perform one or more of the removal processes described above to change the stress regime within the hydrocarbon reservoir 220.

In some embodiments, a well operator may have already completed initial extraction of hydrocarbons from the hydrocarbon reservoir 220 using conventional or unconventional oil drilling techniques, and extracted some of the hydrocarbons within the hydrocarbon reservoir 220. The hydrocarbon reservoir 220 may still hold hydrocarbons within low porosity regions of the hydrocarbon reservoir 220. The cost to extract the remaining hydrocarbons without modifying the formation 10 using one or more of the removal techniques described above may exceed the value of the remaining hydrocarbons, therefore a well operator may use one or more of the material removal processes described above to increase the completion quality of an existing or partially depleted hydrocarbon reservoir.

In some embodiments, a well operator may have begun extraction of hydrocarbons from the hydrocarbon reservoir 220 using conventional or unconventional oil drilling techniques and extracted some of the hydrocarbons within the hydrocarbon reservoir 220 which may be producing hydrocarbons at a low rate. In such an embodiment, a well operator may use one or more material removal processes in the formation 10 to change the stress regime within the formation 10, which may increase the hydrocarbon extraction rate from the hydrocarbon reservoir 220.

FIG. 3 depicts portions of a process for modifying the properties of the formation 10 and, in particular, the hydrocarbon reservoir 220. The drill string 130 has been removed for clarity. In some embodiments, the drill string 130 may be located within the wellbore 120 during the portions of the process depicted in FIG. 3, while in some embodiments, the drill string may be removed from the wellbore 120.

In the embodiment shown in FIG. 3, one or more of the material removal processes has been carried out on the mineral layer 240. The one or more material removal processes has changed the stress regime within the formation 10. In particular, in FIG. 3 the mineral layer 240 of the formation 10 has been weakened such that it provides less support for the shale layer 230 and the hydrocarbon reservoir 220. The weight of the shale layer 230 and hydrocarbon reservoir 220, having less support from the mineral layer 240, may begin to stretch and/or collapse. The force caused by the weight of the formation 10 above the mineral layer 220 and the movement of the shale layer 230 and the hydrocarbon reservoir 220 is represented by the arrows 232. The stretching or collapsing of the hydrocarbon reservoir 220 may cause a change in the stress regime within the hydrocarbon reservoir 220, and cracks, such as cracks 222, may form within the hydrocarbon reservoir 220. The relative movement or displacement of the hydrocarbon reservoir 220, the shale layer 230, and the mineral layer 240 are not shown to scale. The movement or displacement has been exaggerated for clarity.

The cracks 222 in the hydrocarbon reservoir may increase the porosity in the hydrocarbon reservoir 220. The increase in porosity of the hydrocarbon reservoir 220 may cause an increase in the permeability of the hydrocarbon reservoir 220 such that the hydrocarbons within the hydrocarbon reservoir 220 flow from the formation 10 and into the wellbore 120 with less resistance as compared to the flow from the formation 10 and into the wellbore 120 before the one or more material removal processes were carried out on the formation 10. This increase in porosity and permeability may increase the completion quality of a hydrocarbon reservoir 220, such as, for example, a hydrocarbon reservoir 220 with an initially low completion quality, such that extraction using conventional or unconventional drilling techniques without using one or more of the above discussed material removal processes would be technically or cost prohibitive, but may not be technically or cost prohibitive after using one or more of the above discussed material removal processes.

The cracks 222 in the hydrocarbon reservoir 220 may remain open after their formation because the properties of the formation 10 and, in particular, the stress regime within the formation 10, have been changed by the material removal processes such that the cracks 222 do not close. For example, when the mineral layer 240 included salt that was solution mined and removed from the formation 10, the support provided by the salt is removed and the hydrocarbon reservoir 220 may settle. The settling may cause the cracks 222 to form and the cracks 222 may stay open until, for example, the mineral layer 240 is pumped back up to provide support back to the hydrocarbon reservoir 220, or further settling and geologic action closes the cracks 222.

The cracks 222 may not form immediately after a material removal process begins. In some embodiments, the cracks 222 take days, months, or years after the completion of the material removal process has completed to form, such that the completion quality of the hydrocarbon reservoir 220 increases. For example, in some embodiments, after starting material removal, natural geologic processes such as settling, stretching, and compacting of portions of the formation may cause the cracks 222 to form. In some embodiments, the cracks 222 may begin forming during the material removal process such that the completion quality of the hydrocarbon reservoir 220 increases before completion of the material removal processes.

In some embodiments, proppants may be injected into the hydrocarbon reservoir 220 during or after the formation of the cracks 222 within the hydrocarbon reservoir 220. The proppants may become lodged in the cracks 222 and may aid in keeping the cracks open, which may maintain porosity and permeability of the hydrocarbon reservoir 220. The proppants may be injected into the hydrocarbon reservoir 220 though an additional wellbore, such as a wellbore 320 in FIGS. 5 and 6, or through a secondary wellbore, such as the secondary wellbore 140 in FIG. 6.

FIG. 4 depicts portions of a process for modifying the properties of the formation 10 and, in particular, the hydrocarbon reservoir 220. The drill string 130 has been removed for clarity. In some embodiments, the drill string 130 may be located within the wellbore 120 during the portions of the process depicted in FIG. 4, while in some embodiments, the drill string may be removed from the wellbore 120. In FIG. 4 the mineral layer 240 is pumped up, whereby fluid and/or other material is injected from the wellbore 120 and into the mineral layer 240, as represented by arrows 128, to pressurize the mineral layer 240.

The injection of fluid and/or other material may cause an increase in pressure within the mineral layer or may otherwise cause movement or displacement of the shale layer 230 and/or the hydrocarbon reservoir 220, as represented by the arrows 234. The movement or displacement of the hydrocarbon reservoir 220 may increase or lengthen the existing cracks 222 within the hydrocarbon reservoir 220, or may cause additional cracks 222 to form.

Pumping up of the mineral layer 240 may occur before or after the material removal processes discussed above. In some embodiments, after one or more of the material removal processes are conducted on the mineral layer 240, proppants may be injected into the cracks 222 of the hydrocarbon reservoir 220 before pumping up the mineral layer 240. The proppants may act to increase the stress within the hydrocarbon reservoir 220 during the pumping up process and may cause further cracking within the hydrocarbon reservoir. After pumping up the mineral layer 240, at least some of the liquid or other material used in the pumping up process may be removed from the mineral layer 240. Removing the liquid or other material may reduce the pressure within the mineral layer 240.

Multiple material removal processes and pumping up processes may occur. For example, after a first material removal process, such as acidizing the mineral layer 240, a well operator may pump up the mineral layer 240, and then acidize the mineral layer 240 again. Repetition of material removal processes and/or pumping up processes may change the stress regime in the formation 10 and, in particular, the hydrocarbon reservoir 220, through fatigue, e.g., the application and removal of a load or force on the hydrocarbon reservoir 220. As with the material removal processes, the pumping up process may take place before, during, or after initial extraction of hydrocarbons from the hydrocarbon reservoir 220.

FIG. 5 depicts portions of a process for modifying the properties of the formation 10 and, in particular, the hydrocarbon reservoir 220. FIG. 5 depicts a formation 10 after one or more material removal processes and/or pumping up processes have been carried out on the mineral layer 240, and cracks 222 have been formed in the hydrocarbon reservoir 220. In some embodiments, hydraulic fracturing processes may be carried out within the hydrocarbon reservoir 220.

The embodiment for FIG. 5 includes an additional land-based drilling system 300 includes a drilling rig 310 positioned over a wellbore 320 and a drill string 330 for exploring formation 10. In the illustrated embodiment, the wellbore 320 is formed by drilling. Those of ordinary skill in the art given the benefit of this disclosure will appreciate that the subject matter of this disclosure also finds application in rotary drilling and directional drilling applications, and is not limited to land-based rigs.

The drill string 330 is suspended within the wellbore 320 and includes a bottom hole assembly 312. The bottom hole assembly 312 may include one or more tools for hydraulically fracturing the hydraulic reservoir 220 through the wellbore 320.

The wellbore 320 may include one or more sections. For example the wellbore 320 depicted in FIG. 5 includes three sections, a first or vertical section, a second or transition section and a third or horizontal section. The transition section of the wellbore 320 transitions the wellbore from a substantially vertical section to a substantially horizontal section. The horizontal section penetrates through the hydrocarbon reservoir 220. By drilling a horizontal or substantially horizontal wellbore section, the wellbore 320 may penetrate a greater portion of the hydrocarbon reservoir 220 than if the wellbore included a single, vertical section.

Hydraulic fracturing of the hydrocarbon reservoir 220, indicated by the arrows 314, may further increase the porosity and permeability of the hydrocarbon reservoir 220 by inducing additional cracks 222 within the hydrocarbon reservoir 220. The hydraulic fracturing process may take place before, during, or after the material removal processes and/or the pumping up processes discussed above.

FIG. 6 depicts portions of a process for modifying the properties of the formation 10 and, in particular, the hydrocarbon reservoir 220. FIG. 6 depicts a formation 10 after one or more material removal processes and/or pumping up processes have been carried out on the mineral layer 240, and cracks 222 have been formed in the hydrocarbon reservoir 220. In some embodiments, hydraulic fracturing processes may have also been carried out within the hydrocarbon reservoir 220.

An additional land-based drilling system 400 includes a drilling rig 410 that may be positioned over a wellbore 420 and a drill string 430 for exploring formation 10. In the illustrated embodiment, the wellbore 420 is formed by drilling. Those of ordinary skill in the art given the benefit of this disclosure will appreciate that the subject matter of this disclosure also finds application in rotary drilling and directional drilling applications, and is not limited to land-based rigs.

The drill string 430 is suspended within the wellbore 420 and includes a downhole tool 412. The downhole tool 412 may include one or more tools for drilling into the formation, such as a drill bit, or tools for extracting hydrocarbons from the hydrocarbon reservoir 220.

Although the wellbore 420 is depicted as a conventional wellbore including a single vertical section, in some embodiments the wellbore 420 may be an unconventional wellbore that includes one or more transition and horizontal sections. The wellbore 420 may be used for additional hydraulic fracturing of the hydrocarbon reservoir, hydrocarbon extraction from the hydrocarbon reservoir, or other drilling processes.

The wellbore 120 may include a secondary wellbore 140. The secondary wellbore 140 may be used in addition to or in place of one or more of the wellbore 420 and wellbore 320 for exploring the formation 10 and/or extracting hydrocarbons from the hydrocarbon reservoir 220. For example, rather than drilling wellbore 420 and wellbore 320 to hydraulically fracture the hydrocarbon reservoir 220 and to extract the hydrocarbons, a well operator may use the wellbore 120 for material removal or other processes in the mineral layer 240 and hydraulically fracture the hydrocarbon reservoir 220 and extract the hydrocarbons therein through the secondary wellbore 140.

FIG. 7 depicts portions of a process for modifying the properties of the formation 20 and, in particular, the hydrocarbon reservoir 290. The formation 20 may include one or more geologic layers. For example, the formation 20 includes a first geologic layer 260, a hydrocarbon reservoir 290, a second geologic layer that may be a shale layer 280, a mineral layer 270, and a third geologic layer 295.

The first geologic layer 260 may begin at a ground surface 22 and extend through the formation to the mineral layer 270 and the shale layer 280. In some embodiments, the first geologic layer 260 may include one or more additional geologic layers. For example, the first geologic layer 260 may include one or more porous and/or non-porous layers between the ground surface 22 and the hydrocarbon reservoir 220 and the shale layer 280. In some embodiments, the first geologic layer 260 may include one or more additional hydrocarbon reservoirs 290.

The mineral layer 240 may be located above the shale layer 280 and the hydrocarbon reservoir 290 and above the third geologic layer 295. The mineral layer 270 may include deposits of one or more minerals and may include other deposits, such as, for example, water. In particular, the mineral layer 270 may include one or more of salt, limestone, dolomite, and other minerals.

The shale layer 280 is a geologic layer of non-porous or semi-porous shale. In some embodiments, the shale layer 280 is located below the mineral layer 270, as shown in FIG. 7. In some embodiments, the formation 20 may not have a shale layer 280. As shown in FIG. 7, the shale layer 280 separates the hydrocarbon reservoir 290 from the mineral layer 270.

The formation 20 may also include the hydrocarbon reservoir 290. The hydrocarbon reservoir 290 may be located within the formation 20 between the shale layer 280 and the third geologic layer 295. The hydrocarbon reservoir 290 may include oil, natural gas, or a combination of both oil and natural gas. Although depicted as a separate layer, in some embodiments, the hydrocarbon reservoir 290 is incorporated into other geologic layers within the formation 20. Although depicted as having a single hydrocarbon reservoir 290, in FIG. 7, in some embodiments the formation 20 may include more than one hydrocarbon reservoir 290.

The formation 20 may also include a third geologic layer 295. The third geologic layer 295 may begin at the hydrocarbon reservoir 290 and the shale layer 280 and extend through and to the bottom of the formation 20. In some embodiments, the third geologic layer 295 may itself include one or more additional geologic layers. For example, the third geologic layer 295 may include one or more porous and/or non-porous layers and one or more additional hydrocarbon reservoirs 290.

FIG. 7 also illustrates a land-based drilling system 500 includes a drilling rig 510 positioned over a wellbore 520, and a drill string 530 for exploring formation 20. In the illustrated embodiment, the wellbore 520 is formed by drilling. Those of ordinary skill in the art given the benefit of this disclosure will appreciate that the subject matter of this disclosure also finds application in rotary drilling and directional drilling applications, and is not limited to land-based rigs.

The drill string 130 is suspended within the wellbore 120 and includes a downhole tool 512 as part of a bottom hole assembly at its lower, terminal, or bottom end. The downhole tool 512 may include a drill bit. The drill string 530 can also include a variety of other tools, for example, reamers, logging while drilling tools, or other drilling tools. In some embodiments, the drill string may be a wireline tool or other tool, such as the tool associated with acidizing minerals, removing water for the formation 20, solution mining, or vibratory tools.

FIG. 7 also depicts portions of a process for modifying the properties of the formation 20 and, in particular, the hydrocarbon reservoir 290. The process includes assembling a drilling system 500, including erecting the drilling rig 510, and drilling a wellbore 520 using, for example, a drill string 530. The wellbore 520 is drilled into the formation 20 to a depth near the depth of the mineral layer 270. The wellbore 520 may be drilled to include a transition section that transitions the wellbore 520 from the vertical section of the wellbore to a horizontal section. The wellbore 520 may be further extended to include the horizontal section that penetrates through the cross section of the mineral layer 270.

In the embodiment depicted in FIG. 7, the mineral layer 270 is above the hydrocarbon reservoir 290. Material removal processes may be carried out on the mineral layer 270 such that that stress regime within the formation 20, and in particular the hydrocarbon reservoir 290, is changed. Changes in the stress regime may cause movement or displacement of the shale layer 280 and/or the hydrocarbon reservoir 290. Changes in the stress regime may also cause cracks, not shown, to form in the hydrocarbon reservoir 290. The cracks may increase the porosity and permeability of the hydrocarbon reservoir 290.

Changes in the stress regime and increase in the porosity and permeability of the hydrocarbon reservoir 290 may also cause some of the hydrocarbons within the hydrocarbon reservoir 290 to move into the mineral layer 270. The shale layer 280 may resist movement of hydrocarbons from the hydrocarbon reservoir 290 to the mineral layer 270. Formations without shale layer 280 or other impermeable or semi-impermeable layer between the hydrocarbon reservoir 290 and the mineral layer 270 may have greater movement of hydrocarbons between the hydrocarbon reservoir 290 and the mineral layer 270. The movement of hydrocarbons from the hydrocarbon reservoir 290 to the mineral layer 270 may decrease the difficulty in extracting the hydrocarbons as compared to embodiments wherein the hydrocarbons remained within a lower hydrocarbon reservoir.

FIG. 8 depicts portions of a process for modifying the properties of a formation 30 and, in particular, the hydrocarbon reservoir 720. The formation 30 may include one or more geologic layers. For example, the formation 30 includes a first geologic layer 710, a hydrocarbon reservoir 720, a mineral layer 740, and a second geologic layer 750.

The first geologic layer 710 may begin at a ground surface 32 and extend through the formation to the second geologic layer 750. In some embodiments, the first geologic layer 710 may itself include one or more additional geologic layers. For example, the first geologic layer 710 may include one or more porous and/or non-porous layers between the ground surface 32 and the second geologic layer 750. In some embodiments, the first geologic layer 710 may include one or more additional hydrocarbon reservoirs 720.

The formation 30 may also include a second geologic layer 750. The second geologic layer 750 may begin at the bottom of the first geologic layer and extend through and to the bottom of the formation 30. In some embodiments, the second geologic layer 750 may itself include one or more additional geologic layers. For example, the second geologic layer 750 may include one or more porous and/or non-porous layers and one or more additional hydrocarbon reservoirs 720 and/or one or more mineral layers 740.

The mineral layer 740 may be located within the second geologic layer and adjacent, around or partially around the hydrocarbon reservoir 720. The mineral layer 740 may include deposits of one or more minerals and may include other deposits, such as, for example, water. In particular, the mineral layer 740 may include one or more of salt, limestone, dolomite, and other minerals.

The formation 30 may also include the hydrocarbon reservoir 720. The hydrocarbon reservoir 720 may be located within the formation 20 and within the second geologic layer 750. The hydrocarbon reservoir 720 may include oil, natural gas, or a combination of both oil and natural gas. Although depicted as a separate layer, in some embodiments the hydrocarbon reservoir 720 is incorporated into other geologic layers within the formation 30. Although depicted as having a single hydrocarbon reservoir 720, in FIG. 8, in some embodiments the formation 30 may include more than one hydrocarbon reservoir 720.

FIG. 8 also illustrates a land-based drilling system 600 that may include a drilling rig 610 positioned over a wellbore 620, and a drill string 630 for exploring formation 30. In the illustrated embodiment, the wellbore 620 is formed by drilling. Those of ordinary skill in the art given the benefit of this disclosure will appreciate that the subject matter of this disclosure also finds application in rotary drilling and directional drilling applications, and is not limited to land-based rigs.

The drill string 630 is suspended within the wellbore 620 and includes a downhole tool 612 as part of a bottom hole assembly at its lower, terminal, or bottom end. The downhole tool 612 may include a drill bit. The drill string 630 can also include a variety of other tools, for example, reamers, logging while drilling tools, or other drilling tools. In some embodiments, the drill string may be a wireline tool or other tool, such as the tool associated with acidizing minerals, removing water for the formation 30, solution mining, or vibratory tools.

FIG. 8 also depicts portions of a process for modifying the properties of the formation 30 and, in particular, the hydrocarbon reservoir 720. The process includes assembling a drilling system 600, including erecting or assembling the drilling rig 610, and drilling a wellbore 620 using, for example, a drill string 630. The wellbore 620 is drilled into the formation 30 to a depth near the depth of the mineral layer 740.

In the embodiment depicted in FIG. 8, the mineral layer 740 is adjacent the hydrocarbon reservoir 720. Material removal processes may be carried out on the mineral layer 740 such that that stress regime within the formation 30, and in particular the hydrocarbon reservoir 720, is changed. Changes in the stress regime may cause movement or displacement of the hydrocarbon reservoir 720, for example in a direction towards the mineral layer 740. Changes in the stress regime may also cause cracks, not shown, to form in the hydrocarbon reservoir 720. The cracks may increase the porosity and permeability of the hydrocarbon reservoir 720. The increase in porosity and permeability of the hydrocarbon reservoir 720 may increase the rate at which hydrocarbons may be extracted from the hydrocarbon reservoir 720.

In addition to material removal processes, the mineral layer 740 may also be pumped up. One or more of the material removal processes and pumping up of the mineral layer 740 may be repeated to further change the stress regime within the hydrocarbon reservoir. In addition, these processes may be carried out in combination with other processes, such as hydraulic fracturing, for further increasing the extraction of hydrocarbons from the hydrocarbon reservoir 720.

FIG. 9 depicts an embodiment of a method for modifying a formation 800. At block 810, a drilling rig is assembled. Assembling a drilling rig, such as drilling rig 110, may include erecting a mast, assembling a drilling platform, moving a drilling boat or offshore rig over the location for the wellbore, and other tasks associated with preparing a drill site and preparing to drill a wellbore.

At block 820, a wellbore is drilled into a formation. The wellbore may be a convention wellbore, for example, as depicted by the wellbore 620 in FIG. 8, or an unconventional wellbore, for example, as depicted by the wellbore 120 in FIG. 1. The wellbore may include one or more horizontal, vertical, and transition section and may be drilled into a geologic layer of the formation. For example, the wellbore may be drilled into the mineral layer 240 of the formation 10, as depicted in FIG. 1.

Drilling a wellbore into the formation may also include drilling a plurality of wellbores into a formation. For example, in some embodiments, a first wellbore may be drilled into a mineral layer, such as mineral layer 240, a second wellbore may be drilled horizontally into a hydrocarbon reservoir, such as wellbore 320 into hydrocarbon reservoir 220, and third wellbore may be drilled vertically into a geologic layer, such as wellbore 420 into the hydrocarbon reservoir 220, shown in FIG. 6. In some embodiments, the wellbore may include a secondary wellbore such as secondary wellbore 140.

At block 830, material is removed from the formation. Material may be removed from a geologic layer of the formation, for example the mineral layer 240 of the formation 10. The mineral may be removed through one or more material removal processes. For example, in some embodiments, the mineral layer 240 may include a salt deposit. The salt in the salt deposit may be removed using solution mining processes or through mechanical mining processes. In some embodiments, the geologic layer may be a mineral layer that includes carbonate, such as limestone or dolomite. The carbonates within the mineral layer may be removed using an acidizing process, for example, as described in more detail above. In some embodiments, the geologic layer may include water or other liquid that may be removed though pumping or other liquid removal processes.

At block 840, the formation is pressurized. In some embodiments, the formation, and in particular, a geologic layer of a formation, such as a mineral layer 240, may be pressurized or pumped up, whereby fluid and/or other material is injected from a wellbore, such as wellbore 120, and into the mineral layer, for example, as shown and described with respect to FIG. 4, above.

At block 850, the formation is vibrated. In some embodiments, the formation may be vibrated, for example, by using vibrator tools within the formation. As with the material removal processes and the pressurizing process, the vibratory process may be used in addition to one or more of removing water from the formation, acidizing the formation, salt mining the formation, and other processes. The vibratory tools may cause mechanical waves, such as seismic waves to propagate through the formation and in particular a hydrocarbon reservoir, such as the hydrocarbon reservoir 220.

At block 860, the properties of the formation are changed. In some embodiments, the vibration, material removal, and/or pressurization of the formation cause or induce changes in the formation. For example, the mechanical waves caused by the vibration of the formation may travel through the formation and change the stress regime within the formation by, for example, causing fractures within the formation, or causing one or more of the geologic layers to settle or compact and other geologic layers to stretch or expand. In some embodiments, during or after removal of material from a mineral layer in proximity to a hydrocarbon reservoir, the hydrocarbon reservoir may stretch, settle, or expand such that cracks are formed within the hydrocarbon reservoir and the porosity and permeability properties of the reservoir are changed. Changing the properties of the formation may also include increasing the completion quality of a hydrocarbon reservoir within the formation.

At block 870, the formation is hydraulically fractured. Hydraulic fracturing of formation, and in particular a hydrocarbon reservoir, such as the hydrocarbon reservoir 220, may further change the properties of the formation by increasing the porosity and permeability of the hydrocarbon reservoir by inducing additional cracks within the hydrocarbon reservoir.

At block 880, hydrocarbons are extracted from the formation. In hydrocarbon extraction, the hydrocarbons within a hydrocarbon reservoir, such as the hydrocarbon reservoir 220, may be extracted from the formation. Hydrocarbon extraction may occur before, during, or after the pressurization process, the vibratory process, and the hydraulic fracturing process.

A few example embodiments have been described in detail above; however, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the scope of the present disclosure or the appended claims. Accordingly, such modifications are intended to be included in the scope of this disclosure. Likewise, while the disclosure herein contains many specifics, these specifics should not be construed as limiting the scope of the disclosure or of any of the appended claims, but merely as providing information pertinent to one or more specific embodiments that may fall within the scope of the disclosure and the appended claims. Any described features from the various embodiments disclosed may be employed in combination. In addition, other embodiments of the present disclosure may also be devised which lie within the scope of the disclosure and the appended claims. Additions, deletions and modifications to the embodiments that fall within the meaning and scopes of the claims are to be embraced by the claims.

Certain embodiments and features may have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges including the combination of any two values, e.g., the combination of any lower value with any upper value, the combination of any two lower values, or the combination of any two upper values are contemplated. Certain lower limits, upper limits and ranges may appear in one or more claims below. Numerical values are “about” or “approximately” the indicated value, and take into account experimental error, tolerances in manufacturing or operational processes, and other variations that would be expected by a person having ordinary skill in the art.

The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include other possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Methods of Modifying Formation Properties

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