CA2658472C - Plug and related methods for isolating open perforations in horizontal wellbores using ultra lightweight proppant and soluble material - Google Patents
Plug and related methods for isolating open perforations in horizontal wellbores using ultra lightweight proppant and soluble material Download PDFInfo
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- CA2658472C CA2658472C CA2658472A CA2658472A CA2658472C CA 2658472 C CA2658472 C CA 2658472C CA 2658472 A CA2658472 A CA 2658472A CA 2658472 A CA2658472 A CA 2658472A CA 2658472 C CA2658472 C CA 2658472C
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- soluble material
- plug
- fluid
- wellbore
- ultra lightweight
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Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices, or the like
- E21B33/138—Plastering the borehole wall; Injecting into the formation
Abstract
An improved method for building an isolation plug in a horizontal wellbore using a fluid pill pumped into the wellbore at the end of a fracturing treatment. The fluid pill includes a high concentration of an ultra lightweight proppant and soluble material. The fluid pill is pumped down the wellbore until it almost reaches a desire zone. The pumping is then ceased or reduced, allowing the fractures to partially close. The ultra lightweight proppant remains suspended within the fluid pill while stationary. The pumping is then resumed at a very slow rate or as a short pump burst, thus causing the lightweight proppant and soluble material to bridge off until an isolation plug is formed. The plug is removed by dissolving the soluble material with or without performing a cleanout.
Description
Field of the Invention The present invention, in general, relates to improved plugs and related methods for building an isolation plug in a horizontal wellbore at a zone of interest and, more specifically, to utilizing a fluid pill containing a high concentration of ultra lightweight proppant and soluble material in order to form a soluble proppant plug in a horizontal wellbore.
Description of the Related Art New hydrocarbon reserves are increasingly being discovered in lower quality reservoirs, particularly in North America. These lower quality reservoirs require some io form of "stimulation" to increase the production of hydrocarbons from wells in these fields. Fracture stimulating a well to increase the production of hydrocarbons is common practice in the oil and gas industry. Many of these reservoirs require multiple fractures to reach economic production levels and provide effective drainage. After the casing in a zone of interest has been perforated and stimulated, it must be hydraulically isolated before any new zone of interest can be exploited. A zone is often isolated by the insertion and setting of a mechanical plug, hereinafter referred to as a bridge plug, below the zone of interest.
The purpose of the bridge plug is simply to hydraulically isolate that portion of the well from a lower portion (or the rest) of the well. The isolation of the lower zone ensures high pressure fracturing fluid pumped into the well is directed to the zone of interest. The high pressure fracturing fluid is used to fracture the formation at the open perforations in the casing. The high pressure of the fracturing fluid initiates and then propagates a fracture through the formation.
In a vertical well, a bridge plug is typically run into the wellbore using a wireline, but the use of wireline to run a bridge plug in horizontal wellbores is limited to formations that are not overly sensitive to water or excess over-displacement of fluids into the fracture. This is because in order to get the bridge plug into the horizontal wellbore, the bridge plug is connected to wireline and pumped into a horizontal wellbore.
The pumping of the bridge plug into the wellbore displaces the wellbore treatment fluids into the formation, which may have an adverse affect on the hydrocarbon production of the well depending on the rock formation as well as its time sensitivity to the fracture fluid. Alternatively, coiled tubing may be used to push and set the bridge plug into horizontal wellbore to isolate a zone of interest. The use of coiled tubing to run a bridge plug is time consuming and expensive because the coiled tubing needs to be removed from the wellbore between each fracturing process in order to rig up the next bridge plug that will be run for the subsequent treatment.
In an effort to reduce time and costs, another method has been developed to isolate a zone within a horizontal wellbore. This method is to build an isolation plug in the wellbore at the perforation zone such that the plug hydraulically isolates the zone from the upper portion of the wellbore. To build an isolation plug, the end of the fracturing fluid includes a pill of fluid containing an elevated amount of solids, such as sand or proppant, in comparison to the amount of solids present in the fracturing fluid.
The fluid pill is pumped into the well under the fracturing pump rate. The formation at the zone of interest should have already been fractured as the fluid pill approaches the zone of interest because the fluid pill is located at the tail end of the fracturing fluid.
The pumping, and thus displacement of the fracturing fluid, is stopped as the fluid pill reaches the perforation tunnels at the zone of interest. The fluid pill with a high concentration of solids remain stationary within the wellbore with the hope that the solids remain suspended in the fluid pill. The displacement of the fracturing fluid is stopped for a period of time to allow the fractures within the formation to partially close. Once closed or partially closed, the displacement of the fluid pill is resumed, normally at a low rate in comparison to the pump rate during the fracturing process.
The fluid pill is pumped at a low rate moving the fluid pill to the formation face at the perforation tunnel. Typically, the pump rate is set low enough to prevent the fractures from reopening. The pumping of the fluid in the wellbore causes the fluid of the fluid pill to enter the fractures, but the high concentration of solids suspended within the fluid pill screens out against the fractures because the fractures are closed or partially closed.
Subsequently, the suspended solids in the fluid pill begin to bridge off against the fractures. As the process continues, the solids continue to pack off against the perforation tunnels and eventually the solids pack off against other solids in the fluid pill, thereby creating a isolation plug in the wellbore. The slow rate of pumping is continued until the pressure within the wellbore rises indicating that a proper isolation plug has been built within the wellbore.
Building a isolation plug within a horizontal wellbore is a difficult process because any gravitational settling of solids in the wellbore will leave a fluid channel at the top of the hole, and subsequent pumping will simply allow solids and displacement fluid to pass down the `channel" and into the fracture without allowing an isolation plug to form. The fluid pill needs to remain stationary long enough to allow the fractures in the formation to at least partially close and so the fracturing fluid must suspend the solids for at least this period of time. If the solids do not remain suspended and settle out, it is likely that a proper isolation plug will not be achieved. This is because, as the solids settle, clear fluid or fluid without suspended solids becomes located at the top of the horizontal wellbore. As pumping is resumed, the fluid of the fluid pill will simply stream over the solid bed rather than carrying the solids into the perforation tunnel because of io the gap at the top of the horizontal bore.
Failing to build an isolation plug will inevitably require a remedial operation involving a pump down wireline plug or a coiled tubing run. Thus, it is critical the solids remain suspended in the fluid pill while the fluid pill is stationary and/or being propagated adjacent the perforations. However, the methods utilized in prior art isolation techniques have difficulty maintaining suspension of the solids, which leads to costly and time consuming workovers and cleaning jobs. In addition, once an isolation plug has been formed, it must be removed, which also typically requires the time and expense of a cleaning job, which could possibly damage the formation.
In light of the foregoing, it would be desirable to use an ultra lightweight proppant, along with soluble material, to build an isolation plug within a wellbore. It would also be beneficial to provide a method of building an isolation plug utilizing soluble material, wherein the plug dissolves partially or totally, thereby allowing a quick and easy cleaning job or no cleaning job at all.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention provides isolation plugs and related methods for building an isolation plug to hydraulically isolate a portion of a horizontal wellbore. A fluid pill is pumped into the horizontal wellbore at the tail end of a fracturing treatment used to fracture the formation at a zone of interest, the fluid pill containing a high concentration of an ultra lightweight proppant and soluble material.
The soluble material may be, for example, water, acid, gas or oil soluble, or may be some combination of these materials.
The pumping of the displacement fluid pill down the wellbore is varied as the pill reaches the zone of interest, thereby allowing the fractures at the zone of interest to at least partially close. The use of an ultra lightweight proppant helps the proppant to remain suspended within the fluid pill while it is stationary within the wellbore. After the fractures have at least partially closed, the pumping is resumed at a low rate or as a short pump burst, thereby displacing the fluid pill towards the fractures, and eventually creating an isolation plug.
The isolation plug is removed by dissolving or partially dissolving the soluble material. The fluid used to dissolve the isolation plug may be produced from the formation itself or may be introduced into the wellbore from a surface location via some cleanout method. The carrier fluid used in the fluid pill and the displacement fluid used to displace the fluid pill are fluids which would not prematurely dissolve the soluble material before removal of the isolation plug is desired.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a fluid pill located at the tail end of fracturing fluid being displaced down a horizontal wellbore, the fluid pill containing an elevated amount of ultra lightweight proppant and soluble material according to an exemplary embodiment of the present invention;
Figure 2 shows the fluid pill stationary within the horizontal wellbore above the perforations at the zone of interest according to an exemplary embodiment of the present invention;
Figure 3 shows the ultra lightweight proppant and soluble material of a fluid pill beginning to bridge off at the zone of interest according to an exemplary embodiment of the present invention; and Figure 4 shows an isolation plug of ultra lightweight proppant and soluble material isolating a zone of a horizontal wellbore according to an exemplary embodiment of the present invention.
These and other aspects, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the exemplary embodiments, which follow.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
Illustrative embodiments and methods of the present invention are described below as they might be employed in the use of ultra lightweight and soluble material to build an isolation plug in a horizontal wellbore. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment or method, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. Further aspects and advantages of the various embodiments of the invention will become apparent from consideration of the following description and drawings.
Figure 1 illustrates a horizontal wellbore that includes a casing 10 that has been perforated 35. The casing 10 may have been perforated by a various number of methods as would be appreciated by one of ordinary skill in the art. A horizontal well, as used in this disclosure, refers to any deviated well. These wells can include, for example, any well which deviates from a true vertical axis more than 60 degrees. Those ordinarily skilled in the art having the benefit of this disclosure will understand that all such wells are encompassed by the term "horizontal well." The use of a cased horizontal wellbore in Figures 1-4 is for illustrative purposes only, as the disclosed invention is also applicable in horizontal open wellbores as would be recognized by one of ordinary skill in the art having the benefit of this disclosure.
According to an exemplary embodiment of the present invention, after the casing 10 has been perforated, fracturing fluid, including proppant 30, is pumped down the casing under high pressure creating fractures 40 in the well formation at the perforations 35 in the casing 10. A fluid pill 50 is located at the tail end of the proppant laden fracturing fluid 30 and is displaced (denoted by arrows 20 of FIGS. 1 & 3) down the horizontal wellbore by displacement fluid 25 pumped down the wellbore. Fluid pill 50 contains ultra lightweight proppant which remains substantially suspended while the fluid pill 50 is stationary within the horizontal wellbore, thereby bridging off and forming an isolation plug with the horizontal wellbore. The concentration of ultra lightweight proppant within the fluid pill 50 is higher in comparison to the concentration of proppant 30 used in the fracturing fluid. For purposes of this disclosure, please note the terms io "suspended" and "substantially suspended" are used interchangeably; as such, they could refer to ultra lightweight proppants and/or ultra lightweight proppant mixtures capable of partial or complete suspension.
The ultra lightweight proppant used in fluid pill 50 may be, for example, neutrally buoyant proppant; proppant that has approximately 50% the density of sand conventionally used as proppant in the fracturing of a well formation; some mixture of lightweight proppant and fracturing proppant; or some other proppant which is lighter than sand. The ultra lightweight proppant, for example, may have a specific gravity of 1.08 to 1.75. The density of the ultra lightweight proppant may be varied according to the fracturing fluid used in the process to ensure that the ultra lightweight proppant does not settle out of the fluid pill 50 while it is stationary within the wellbore. Those ordinarily skilled in the art having the benefit of this disclosure will realize that a variety r i of proppant mixtures with varying specific gravities and densities may be used within the scope of the present invention.
In one exemplary embodiment, such ultra lightweight proppant can be, for example, the neutrally buoyant particulate material disclosed in U.S. Patent No. 6,364,018 entitled "Lightweight Methods and Compositions for Well Treating" issued April 2, 2002 or in U.S.
Patent No. 7,426,961 entitled "Method of Treating Subterranean Formations with Porous Ceramic Particulate Materials" issued September 23, 2008 each being assigned to BJ Services Company. Likewise, the ultra lightweight proppant may be the neutrally buoyant particulate material disclosed in U.S. Patent No. 7,713,918 entitled "Method of Treating Subterranean Formations with Porous Ceramic Particulate Materials" issued May 11, 2010. The above patent and patent applications disclose the use of a neutrally buoyant particulate material in the stimulation of a well.
In yet another exemplary embodiment, the ultra lightweight proppant in fluid pill 50 is a neutrally buoyant resin coated material that may be pumped downhole with the fluid pill 50 in order to bridge off against the formation to form a plug. There are numerous materials that may be used in this application as would be recognized by one of ordinary skill in the art having the benefit of this disclosure. For example, one type of neutrally buoyant resin coated material is LITEPROPTM offered by BJ Services Company of Houston, Texas. Additionally, a neutrally buoyant plastic such as divinylbenzene ("DVB") may be used in this application.
Description of the Related Art New hydrocarbon reserves are increasingly being discovered in lower quality reservoirs, particularly in North America. These lower quality reservoirs require some io form of "stimulation" to increase the production of hydrocarbons from wells in these fields. Fracture stimulating a well to increase the production of hydrocarbons is common practice in the oil and gas industry. Many of these reservoirs require multiple fractures to reach economic production levels and provide effective drainage. After the casing in a zone of interest has been perforated and stimulated, it must be hydraulically isolated before any new zone of interest can be exploited. A zone is often isolated by the insertion and setting of a mechanical plug, hereinafter referred to as a bridge plug, below the zone of interest.
The purpose of the bridge plug is simply to hydraulically isolate that portion of the well from a lower portion (or the rest) of the well. The isolation of the lower zone ensures high pressure fracturing fluid pumped into the well is directed to the zone of interest. The high pressure fracturing fluid is used to fracture the formation at the open perforations in the casing. The high pressure of the fracturing fluid initiates and then propagates a fracture through the formation.
In a vertical well, a bridge plug is typically run into the wellbore using a wireline, but the use of wireline to run a bridge plug in horizontal wellbores is limited to formations that are not overly sensitive to water or excess over-displacement of fluids into the fracture. This is because in order to get the bridge plug into the horizontal wellbore, the bridge plug is connected to wireline and pumped into a horizontal wellbore.
The pumping of the bridge plug into the wellbore displaces the wellbore treatment fluids into the formation, which may have an adverse affect on the hydrocarbon production of the well depending on the rock formation as well as its time sensitivity to the fracture fluid. Alternatively, coiled tubing may be used to push and set the bridge plug into horizontal wellbore to isolate a zone of interest. The use of coiled tubing to run a bridge plug is time consuming and expensive because the coiled tubing needs to be removed from the wellbore between each fracturing process in order to rig up the next bridge plug that will be run for the subsequent treatment.
In an effort to reduce time and costs, another method has been developed to isolate a zone within a horizontal wellbore. This method is to build an isolation plug in the wellbore at the perforation zone such that the plug hydraulically isolates the zone from the upper portion of the wellbore. To build an isolation plug, the end of the fracturing fluid includes a pill of fluid containing an elevated amount of solids, such as sand or proppant, in comparison to the amount of solids present in the fracturing fluid.
The fluid pill is pumped into the well under the fracturing pump rate. The formation at the zone of interest should have already been fractured as the fluid pill approaches the zone of interest because the fluid pill is located at the tail end of the fracturing fluid.
The pumping, and thus displacement of the fracturing fluid, is stopped as the fluid pill reaches the perforation tunnels at the zone of interest. The fluid pill with a high concentration of solids remain stationary within the wellbore with the hope that the solids remain suspended in the fluid pill. The displacement of the fracturing fluid is stopped for a period of time to allow the fractures within the formation to partially close. Once closed or partially closed, the displacement of the fluid pill is resumed, normally at a low rate in comparison to the pump rate during the fracturing process.
The fluid pill is pumped at a low rate moving the fluid pill to the formation face at the perforation tunnel. Typically, the pump rate is set low enough to prevent the fractures from reopening. The pumping of the fluid in the wellbore causes the fluid of the fluid pill to enter the fractures, but the high concentration of solids suspended within the fluid pill screens out against the fractures because the fractures are closed or partially closed.
Subsequently, the suspended solids in the fluid pill begin to bridge off against the fractures. As the process continues, the solids continue to pack off against the perforation tunnels and eventually the solids pack off against other solids in the fluid pill, thereby creating a isolation plug in the wellbore. The slow rate of pumping is continued until the pressure within the wellbore rises indicating that a proper isolation plug has been built within the wellbore.
Building a isolation plug within a horizontal wellbore is a difficult process because any gravitational settling of solids in the wellbore will leave a fluid channel at the top of the hole, and subsequent pumping will simply allow solids and displacement fluid to pass down the `channel" and into the fracture without allowing an isolation plug to form. The fluid pill needs to remain stationary long enough to allow the fractures in the formation to at least partially close and so the fracturing fluid must suspend the solids for at least this period of time. If the solids do not remain suspended and settle out, it is likely that a proper isolation plug will not be achieved. This is because, as the solids settle, clear fluid or fluid without suspended solids becomes located at the top of the horizontal wellbore. As pumping is resumed, the fluid of the fluid pill will simply stream over the solid bed rather than carrying the solids into the perforation tunnel because of io the gap at the top of the horizontal bore.
Failing to build an isolation plug will inevitably require a remedial operation involving a pump down wireline plug or a coiled tubing run. Thus, it is critical the solids remain suspended in the fluid pill while the fluid pill is stationary and/or being propagated adjacent the perforations. However, the methods utilized in prior art isolation techniques have difficulty maintaining suspension of the solids, which leads to costly and time consuming workovers and cleaning jobs. In addition, once an isolation plug has been formed, it must be removed, which also typically requires the time and expense of a cleaning job, which could possibly damage the formation.
In light of the foregoing, it would be desirable to use an ultra lightweight proppant, along with soluble material, to build an isolation plug within a wellbore. It would also be beneficial to provide a method of building an isolation plug utilizing soluble material, wherein the plug dissolves partially or totally, thereby allowing a quick and easy cleaning job or no cleaning job at all.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention provides isolation plugs and related methods for building an isolation plug to hydraulically isolate a portion of a horizontal wellbore. A fluid pill is pumped into the horizontal wellbore at the tail end of a fracturing treatment used to fracture the formation at a zone of interest, the fluid pill containing a high concentration of an ultra lightweight proppant and soluble material.
The soluble material may be, for example, water, acid, gas or oil soluble, or may be some combination of these materials.
The pumping of the displacement fluid pill down the wellbore is varied as the pill reaches the zone of interest, thereby allowing the fractures at the zone of interest to at least partially close. The use of an ultra lightweight proppant helps the proppant to remain suspended within the fluid pill while it is stationary within the wellbore. After the fractures have at least partially closed, the pumping is resumed at a low rate or as a short pump burst, thereby displacing the fluid pill towards the fractures, and eventually creating an isolation plug.
The isolation plug is removed by dissolving or partially dissolving the soluble material. The fluid used to dissolve the isolation plug may be produced from the formation itself or may be introduced into the wellbore from a surface location via some cleanout method. The carrier fluid used in the fluid pill and the displacement fluid used to displace the fluid pill are fluids which would not prematurely dissolve the soluble material before removal of the isolation plug is desired.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a fluid pill located at the tail end of fracturing fluid being displaced down a horizontal wellbore, the fluid pill containing an elevated amount of ultra lightweight proppant and soluble material according to an exemplary embodiment of the present invention;
Figure 2 shows the fluid pill stationary within the horizontal wellbore above the perforations at the zone of interest according to an exemplary embodiment of the present invention;
Figure 3 shows the ultra lightweight proppant and soluble material of a fluid pill beginning to bridge off at the zone of interest according to an exemplary embodiment of the present invention; and Figure 4 shows an isolation plug of ultra lightweight proppant and soluble material isolating a zone of a horizontal wellbore according to an exemplary embodiment of the present invention.
These and other aspects, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the exemplary embodiments, which follow.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
Illustrative embodiments and methods of the present invention are described below as they might be employed in the use of ultra lightweight and soluble material to build an isolation plug in a horizontal wellbore. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment or method, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. Further aspects and advantages of the various embodiments of the invention will become apparent from consideration of the following description and drawings.
Figure 1 illustrates a horizontal wellbore that includes a casing 10 that has been perforated 35. The casing 10 may have been perforated by a various number of methods as would be appreciated by one of ordinary skill in the art. A horizontal well, as used in this disclosure, refers to any deviated well. These wells can include, for example, any well which deviates from a true vertical axis more than 60 degrees. Those ordinarily skilled in the art having the benefit of this disclosure will understand that all such wells are encompassed by the term "horizontal well." The use of a cased horizontal wellbore in Figures 1-4 is for illustrative purposes only, as the disclosed invention is also applicable in horizontal open wellbores as would be recognized by one of ordinary skill in the art having the benefit of this disclosure.
According to an exemplary embodiment of the present invention, after the casing 10 has been perforated, fracturing fluid, including proppant 30, is pumped down the casing under high pressure creating fractures 40 in the well formation at the perforations 35 in the casing 10. A fluid pill 50 is located at the tail end of the proppant laden fracturing fluid 30 and is displaced (denoted by arrows 20 of FIGS. 1 & 3) down the horizontal wellbore by displacement fluid 25 pumped down the wellbore. Fluid pill 50 contains ultra lightweight proppant which remains substantially suspended while the fluid pill 50 is stationary within the horizontal wellbore, thereby bridging off and forming an isolation plug with the horizontal wellbore. The concentration of ultra lightweight proppant within the fluid pill 50 is higher in comparison to the concentration of proppant 30 used in the fracturing fluid. For purposes of this disclosure, please note the terms io "suspended" and "substantially suspended" are used interchangeably; as such, they could refer to ultra lightweight proppants and/or ultra lightweight proppant mixtures capable of partial or complete suspension.
The ultra lightweight proppant used in fluid pill 50 may be, for example, neutrally buoyant proppant; proppant that has approximately 50% the density of sand conventionally used as proppant in the fracturing of a well formation; some mixture of lightweight proppant and fracturing proppant; or some other proppant which is lighter than sand. The ultra lightweight proppant, for example, may have a specific gravity of 1.08 to 1.75. The density of the ultra lightweight proppant may be varied according to the fracturing fluid used in the process to ensure that the ultra lightweight proppant does not settle out of the fluid pill 50 while it is stationary within the wellbore. Those ordinarily skilled in the art having the benefit of this disclosure will realize that a variety r i of proppant mixtures with varying specific gravities and densities may be used within the scope of the present invention.
In one exemplary embodiment, such ultra lightweight proppant can be, for example, the neutrally buoyant particulate material disclosed in U.S. Patent No. 6,364,018 entitled "Lightweight Methods and Compositions for Well Treating" issued April 2, 2002 or in U.S.
Patent No. 7,426,961 entitled "Method of Treating Subterranean Formations with Porous Ceramic Particulate Materials" issued September 23, 2008 each being assigned to BJ Services Company. Likewise, the ultra lightweight proppant may be the neutrally buoyant particulate material disclosed in U.S. Patent No. 7,713,918 entitled "Method of Treating Subterranean Formations with Porous Ceramic Particulate Materials" issued May 11, 2010. The above patent and patent applications disclose the use of a neutrally buoyant particulate material in the stimulation of a well.
In yet another exemplary embodiment, the ultra lightweight proppant in fluid pill 50 is a neutrally buoyant resin coated material that may be pumped downhole with the fluid pill 50 in order to bridge off against the formation to form a plug. There are numerous materials that may be used in this application as would be recognized by one of ordinary skill in the art having the benefit of this disclosure. For example, one type of neutrally buoyant resin coated material is LITEPROPTM offered by BJ Services Company of Houston, Texas. Additionally, a neutrally buoyant plastic such as divinylbenzene ("DVB") may be used in this application.
In addition to the ultra lightweight proppant described above, fluid pill 50 also contains soluble material. The soluble material utilized, for example, is one which can be dissolved in a formation fluid or cleaned out in a fluid introduced into the wellbore.
Examples of soluble materials include those which are oil, water, or acid soluble, such as those utilized in diversion techniques as understood by those ordinarily skilled in the art.
Benefits of utilizing soluble materials in fluid pill 50 include a quick and more efficient cleanout time, which will be discussed in more detail later in this description. In addition, the majority of solids disposed at the surface will also be eliminated through the use of the soluble material.
In an exemplary embodiment, the soluble material is a water soluble salt such as, for example, sodium chloride, potassium chloride, or calcium chloride. In an alternative embodiment, the soluble material is an acid soluble material such as, for example, calcium carbonate or iron carbonate. In yet another exemplary embodiment, the soluble material is an oil soluble material, such as benzoic acid, resins, waxes, or naphthalene.
Yet another embodiment includes a gas soluble material, such as naphthalene or aluminum chloride. Moreover, yet another exemplary embodiment includes a combination of one or more different soluble materials selected, for example, from those discussed above. Those of ordinary skill in the art having the benefit of this disclosure realize there are a variety of other soluble materials which may be utilized to form an isolation plug in accordance with the present invention.
In this exemplary embodiment, fluid pill 50 contains a mixture of ultra lightweight proppant and soluble material. As discussed above, the soluble material can be a variety of materials, such as those which are oil, water, gas, or acid soluble. In an exemplary embodiment, such mixture of ultra lightweight proppant and soluble material can be 50-80% soluble material by volume, with the remaining volume being comprised of ultra lightweight proppant. Those ordinarily skilled in the art having the benefit of this disclosure realize there are a number of different mixture volumes which may be utilized in accordance with the present invention.
In yet another exemplary embodiment, fluid pill 50 contains a mixture of conventional fracturing proppant (such as, for example, Ottawa Sand), ultra lightweight proppant, and soluble material. Such an ultra lightweight proppant mixture, for example, io can be approximately 30% ultra lightweight proppant, 60% soluble material, and approximately 10% fracturing proppant (such as, for example, Ottawa Sand) by total plug weight. The ultra lightweight proppant used herein could be FLEXSANDTM, while the fracturing proppant could be conventional Ottawa sand, both products offered by BJ
Services Company of Houston, Texas. Please note, however, that those ordinarily skilled in the art having the benefit of this disclosure will recognize that a variety of mixtures may be utilized within the scope of this invention. Besides sand, bauxite and other ceramic proppants (e.g. econoprop, carbolite, carboprop, interprop, etc.), other types of fracturing proppant that can be mixed with the ultra lightweight proppant and soluble material include LITEPROPTM 108, LITEPROPTM 125, LITEPROPTM 175 and FLEXSANDTM, all manufactured and marketed by BJ Services Company of Houston, Texas.
Examples of soluble materials include those which are oil, water, or acid soluble, such as those utilized in diversion techniques as understood by those ordinarily skilled in the art.
Benefits of utilizing soluble materials in fluid pill 50 include a quick and more efficient cleanout time, which will be discussed in more detail later in this description. In addition, the majority of solids disposed at the surface will also be eliminated through the use of the soluble material.
In an exemplary embodiment, the soluble material is a water soluble salt such as, for example, sodium chloride, potassium chloride, or calcium chloride. In an alternative embodiment, the soluble material is an acid soluble material such as, for example, calcium carbonate or iron carbonate. In yet another exemplary embodiment, the soluble material is an oil soluble material, such as benzoic acid, resins, waxes, or naphthalene.
Yet another embodiment includes a gas soluble material, such as naphthalene or aluminum chloride. Moreover, yet another exemplary embodiment includes a combination of one or more different soluble materials selected, for example, from those discussed above. Those of ordinary skill in the art having the benefit of this disclosure realize there are a variety of other soluble materials which may be utilized to form an isolation plug in accordance with the present invention.
In this exemplary embodiment, fluid pill 50 contains a mixture of ultra lightweight proppant and soluble material. As discussed above, the soluble material can be a variety of materials, such as those which are oil, water, gas, or acid soluble. In an exemplary embodiment, such mixture of ultra lightweight proppant and soluble material can be 50-80% soluble material by volume, with the remaining volume being comprised of ultra lightweight proppant. Those ordinarily skilled in the art having the benefit of this disclosure realize there are a number of different mixture volumes which may be utilized in accordance with the present invention.
In yet another exemplary embodiment, fluid pill 50 contains a mixture of conventional fracturing proppant (such as, for example, Ottawa Sand), ultra lightweight proppant, and soluble material. Such an ultra lightweight proppant mixture, for example, io can be approximately 30% ultra lightweight proppant, 60% soluble material, and approximately 10% fracturing proppant (such as, for example, Ottawa Sand) by total plug weight. The ultra lightweight proppant used herein could be FLEXSANDTM, while the fracturing proppant could be conventional Ottawa sand, both products offered by BJ
Services Company of Houston, Texas. Please note, however, that those ordinarily skilled in the art having the benefit of this disclosure will recognize that a variety of mixtures may be utilized within the scope of this invention. Besides sand, bauxite and other ceramic proppants (e.g. econoprop, carbolite, carboprop, interprop, etc.), other types of fracturing proppant that can be mixed with the ultra lightweight proppant and soluble material include LITEPROPTM 108, LITEPROPTM 125, LITEPROPTM 175 and FLEXSANDTM, all manufactured and marketed by BJ Services Company of Houston, Texas.
Further referring to the exemplary embodiment of Figure 1, after the hydraulic pressure of the fracturing fluid fractures the formation, the proppant located in the fracturing fluid 30 enters the fractures 40 helping to hold the fractures open. The pumping of the fluid 25 in the wellbore is stopped or reduced as the fluid pill 50 approaches the perforations 35 in the casing 10 and the fluid pill 50 becomes stationary as shown in Figure 2. Given the properties described above, the ultra lightweight proppant remains suspended within the fluid pill 50 while the fluid pill 50 is stationary within the wellbore.
The fluid pill 50 needs to remain stationary for a period of time long enough to allow the fractures 40 in the formation to close or partially close. The amount of time needed may vary depending on various factors, including the composition of the formation and various components of the fracturing fluid, such as the type and concentration of polymer in the fracturing fluid, the degree of crosslinking, amount of breaker, volumes of fluid used etc. Various computer models may be used to estimate the fracture closure time after the pumping has stopped as would be appreciated by one of ordinary skill in the art.
Referring to Figures 3 and 4, once the fractures 40 have closed or partially closed, the pumping of the displacement fluid 25 is varied based upon whether fluid pill 50 is comprised of ultra lightweight proppant and soluble material only or comprised of ultra lightweight proppant, fracturing proppant and soluble material. When fluid pill 50 is comprised of only ultra lightweight proppant and soluble material, the pumping of displacement fluid 25 is resumed at a low rate, as shown by the arrows 21 in Figure 3, to slowly displace the fluid pill 50 down the casing 10. The slow pumping rate of the displacement fluid 25 should be low enough to prevent the fractures 40 from reopening and should be at a rate lower than the pumping rate used during the fracturing process.
The pumping rate can be adjusted based on the size of the casing, the length of the horizontal well and the size of the fluid pill in order to limit the amount of solids dropped out of the fluid pill 50 during placement. Those skilled in the art having the benefit of this disclosure realize there are any variety of computer models and methods by which these adjustments may be accomplished.
However, in the alternative, if fluid pill 50 is comprised of an ultra lightweight proppant mixture and soluble material as described previously, the pumping of displacement fluid 25 may be resumed as a short pumping burst. This pumping burst rate, for example, may be the pumping rate used during fracturing operations.
This short pump burst involves bringing the pump rate up from zero to substantially the fracturing rate as quickly as possible for a short duration. Once this is done, a rapid increase in pressure will be observed at the surface if the fluid pill 50 bridges off against the fracture.
If no pressure increase is observed, then the fracture has not been plugged and the short pumping burst is repeated. However, once a sufficient pressure increase is observed, the fracture has been plugged as discussed below.
In either event, as the fluid pill 50 is slowly displaced (or displaced via a short pumping burst), the ultra lightweight proppant and soluble material will be displaced towards the perforations 35 in the casing 10 and the fractures 40 in the formation. Since the fractures 40 are already closed or partially closed and full of proppant 30 from the fracturing process, the ultra lightweight proppant is at least partially prevented from entering fractures 40. However, the water, or other carrier fluid, of the fluid pill 50 is able to flow into the fractures 40 causing the fluid pill 50 to dehydrate. As illustrated in Figure 3, the dehydration of the fluid pill 50 in combination with the very slow pumping of the displacement fluid 25 causes the ultra lightweight proppant and soluble material to begin to bridge off 60.
In yet another exemplary embodiment, in order to promote the bridging off of the ultra lightweight proppant and soluble material, an ultra lightweight proppant may be selected having a larger diameter than the diameter of the proppant 30 used in the io fracturing fluid. The larger diameter of the ultra lightweight proppant further prevents the entrance of the ultra lightweight proppant into the fractures 40 promoting the ultra lightweight proppant to bridge off 60 against itself. The use of larger diameter ultra lightweight proppants is made possible because they can be suspended just as easily as the smaller diameter sized material unlike conventional heavier weight proppants where large sized proppants settle much more quickly.
Referring to Figure 4, as the displacement fluid 25 is slowly pumped (or displaced via the short pumping burst), the ultra lightweight proppant and soluble material continues to bridge off until a plug 70 is built up in the wellbore. The displacement fluid is continued to be pumped into the wellbore, which results in a pressure increase 20 which can be detected by various means known in the art. Once a certain pressure increase is detected, an operator and/or other monitoring means will understand/determine this indicates the wellbore has been hydraulically isolated with the plug 70.
In an exemplary embodiment, the carrier fluid utilized in fluid pill 50 is selected based upon the soluble material utilized so that the soluble material will not be prematurely dissolved. For example, if a water soluble material is used in fluid pill 50, water is not used as the carrier fluid. To do so may prematurely dissolve the soluble material in fluid pill 50 or in plug 70 after it has been created. In yet another example, oil would not be utilized as a carrier fluid for pill 50 if an oil soluble material is utilized.
Those ordinarily skilled in the art having the benefit of this disclosure realize there are a variety of carrier fluids, such as brines, which could be utilized to avoid prematurely dissolving plug 70.
In yet another exemplary embodiment, the displacement fluid 25 utilized to displace fluid pill 50 is also selected based upon the soluble material in order to avoid prematurely dissolving the soluble material. For example, if water soluble material is is used in fluid pill 50, water would not be utilized as displacement fluid 25. To do so may result in prematurely dissolving the water soluble material of fluid pill 50 before plug 70 can be created (or may prematurely dissolve plug 70). In the alternative embodiment, the same fluid is used as both the carrier and displacement fluid 25.
Further referring to the exemplary embodiment of FIG. 4, once plug 70 has been created, the zone is isolated. In accordance with the present invention, removal of plug 70 may be achieved via formation fluids or fluid introduced into the wellbore.
These fluids will dissolve plug 70 completely or dissolve plug 70 enough to allow removal of plug 70. For example, if water soluble material was utilized, the soluble material in plug 70 may be dissolved over time by water produced out of the formation. In the event an oil soluble material is utilized, the soluble material in plug 70 may be dissolved over time by production fluids. In some wells, once the soluble material has dissolved, the remaining lightweight proppant may simply flow out of the wellbore as a result of the downhole pressures, or may not inhibit production, thereby alleviating the need for a clean out of the ultra lightweight proppant and other solids, such as fracturing proppant, if utilized.
In the event clean out is required, such as a coiled tubing cleanout, fluids will be introduced into the well which will dissolve the plug 70. In either event, the use of soluble material will make the clean out quick and efficient, as well as eliminate the majority of solids disposed at the surface. Those ordinarily skilled in this art having the benefit of this disclosure realize there are a variety of clean out methods which may be utilized with the present invention. Moreover, those ordinarily skilled in the art having the benefit of this disclosure realize the time required to dissolve the soluble material is based upon a number of factors, such as well conditions, and that such time periods can be determined based upon known methods.
An exemplary method of the present invention includes a method for utilizing an isolation plug in a horizontal wellbore, the method comprising the steps of pumping a fluid pill into the horizontal wellbore, the fluid pill comprising ultra lightweight proppant and soluble material, the ultra lightweight proppant being capable of remaining suspended in the fluid pill; pumping a displacement fluid down the wellbore to displace the fluid pill; varying a pumping rate of the displacement fluid such that at least one fracture in a zone of the horizontal wellbore is allowed to at least partially close, the ultra lightweight proppant remaining suspended within the fluid pill; pumping the displacement fluid down the horizontal wellbore to slowly displace the fluid pill after the at least one fracture in the zone has at least partially closed; at least partially preventing the ultra lightweight proppant from entering the at least one fracture in the zone, wherein the ultra lightweight proppant and soluble material bridges off forming a plug within the wellbore; and subsequently removing the plug from the wellbore.
In yet another exemplary method, the soluble material comprises a water, acid, gas, or oil soluble material. The soluble material may also comprise a combination of two or more soluble materials. In yet another method, the step of removing the plug is accomplished by at least partially dissolving the soluble material in the plug. In another exemplary method, the step of at least partially dissolving the soluble material is achieved through the use of fluids being produced out of a formation. In the alternative, the step of at least partially dissolving the soluble material is achieved through the use of fluids being introduced into the wellbore from a surface location.
In yet another exemplary method, the soluble material in the plug is at least partially dissolved without performing a cleanout of the wellbore. In another method, the step of removing the plug from the wellbore is achieved by the steps of at least partially dissolving the soluble material in the plug; and removing the ultra lightweight proppant using fluids introduced into the wellbore from a surface location. In yet another exemplary method, the method further comprises the step of selecting at least one of a carrier fluid for the fluid pill or a displacement fluid for the fluid pill which would not prematurely dissolve the soluble material.
Yet another exemplary method of the present invention provides a method for utilizing an isolation plug in a horizontal wellbore, the method comprising the steps of suspending ultra lightweight proppant within a fluid pill, the fluid pill also comprising soluble material; displacing the fluid pill down the horizontal wellbore;
allowing at least one fracture in a zone of the horizontal wellbore to at least partially close;
slowing a displacement rate of the fluid pill after the at least one fracture in the zone has at least partially closed; at least partially preventing the ultra lightweight proppant from entering the at least one fracture in the zone, wherein the ultra lightweight proppant and soluble material bridges off forming a plug within the wellbore; and removing the plug.
In yet another method, the step of removing the plug is accomplished by at least partially dissolving the soluble material in the plug. In another exemplary method, the step of removing the plug is achieved without performing a cleanout of the wellbore. In the alternative, the step of removing the plug is achieved by the steps of at least partially dissolving the soluble material in the plug and removing the ultra lightweight proppant using fluids introduced into the wellbore from a surface location.
Yet another exemplary method of the present invention provides a method of using an ultra lightweight proppant and soluble material in forming a plug within a horizontal wellbore, the method comprising the steps of suspending ultra lightweight proppant within a fluid pill, the ultra lightweight proppant capable of remaining suspended while fluid pill is pumped through the horizontal wellbore, the fluid pill also comprising soluble material; pumping the fluid pill to a location adjacent a zone in the wellbore, and plugging the zone by forming a plug using the ultra lightweight proppant and soluble material, whereby the plug can be removed by at least partially dissolving the soluble material.
Yet another exemplary method further comprises the step of unplugging the zone by at least partially dissolving the soluble material using fluids being produced from the wellbore. Yet another exemplary method comprises the step of unplugging the zone by at least partially dissolving the soluble material using fluids communicated from a surface location. Another method may further comprise the step of unplugging the zone by at least partially dissolving the plug without performing a cleanout of the wellbore. Yet another method further comprises the step of selecting at least one of a carrier fluid for the fluid pill or a displacement fluid for the fluid pill which would not prematurely dissolve the soluble material. In yet another exemplary method, the carrier and displacement fluids are the same fluids.
An exemplary embodiment of the present invention provides an isolation plug for use in a horizontal wellbore, the plug comprising ultra lightweight proppant adapted to remain suspended in a fluid pill used to form the plug; and soluble material, wherein the plug is adapted to be removed by at least partially dissolving the soluble material. In another exemplary embodiment, the soluble material comprises at least one of an oil, water, gas or acid soluble material. In yet another exemplary embodiment, the soluble material in the plug is adapted to be at least partially dissolved without requiring a clean out of the horizontal wellbore. In another embodiment, the soluble material in the plug is adapted to be at least partially dissolved by fluids being produced out of a formation. In yet another exemplary embodiment, the soluble material in the plug is adapted to be at least partially dissolved by fluids being introduced into the horizontal wellbore.
Although various embodiments have been shown and described, the invention is not so limited and will be understood to include all such modifications and variations as would be apparent to one skilled in the art. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.
The fluid pill 50 needs to remain stationary for a period of time long enough to allow the fractures 40 in the formation to close or partially close. The amount of time needed may vary depending on various factors, including the composition of the formation and various components of the fracturing fluid, such as the type and concentration of polymer in the fracturing fluid, the degree of crosslinking, amount of breaker, volumes of fluid used etc. Various computer models may be used to estimate the fracture closure time after the pumping has stopped as would be appreciated by one of ordinary skill in the art.
Referring to Figures 3 and 4, once the fractures 40 have closed or partially closed, the pumping of the displacement fluid 25 is varied based upon whether fluid pill 50 is comprised of ultra lightweight proppant and soluble material only or comprised of ultra lightweight proppant, fracturing proppant and soluble material. When fluid pill 50 is comprised of only ultra lightweight proppant and soluble material, the pumping of displacement fluid 25 is resumed at a low rate, as shown by the arrows 21 in Figure 3, to slowly displace the fluid pill 50 down the casing 10. The slow pumping rate of the displacement fluid 25 should be low enough to prevent the fractures 40 from reopening and should be at a rate lower than the pumping rate used during the fracturing process.
The pumping rate can be adjusted based on the size of the casing, the length of the horizontal well and the size of the fluid pill in order to limit the amount of solids dropped out of the fluid pill 50 during placement. Those skilled in the art having the benefit of this disclosure realize there are any variety of computer models and methods by which these adjustments may be accomplished.
However, in the alternative, if fluid pill 50 is comprised of an ultra lightweight proppant mixture and soluble material as described previously, the pumping of displacement fluid 25 may be resumed as a short pumping burst. This pumping burst rate, for example, may be the pumping rate used during fracturing operations.
This short pump burst involves bringing the pump rate up from zero to substantially the fracturing rate as quickly as possible for a short duration. Once this is done, a rapid increase in pressure will be observed at the surface if the fluid pill 50 bridges off against the fracture.
If no pressure increase is observed, then the fracture has not been plugged and the short pumping burst is repeated. However, once a sufficient pressure increase is observed, the fracture has been plugged as discussed below.
In either event, as the fluid pill 50 is slowly displaced (or displaced via a short pumping burst), the ultra lightweight proppant and soluble material will be displaced towards the perforations 35 in the casing 10 and the fractures 40 in the formation. Since the fractures 40 are already closed or partially closed and full of proppant 30 from the fracturing process, the ultra lightweight proppant is at least partially prevented from entering fractures 40. However, the water, or other carrier fluid, of the fluid pill 50 is able to flow into the fractures 40 causing the fluid pill 50 to dehydrate. As illustrated in Figure 3, the dehydration of the fluid pill 50 in combination with the very slow pumping of the displacement fluid 25 causes the ultra lightweight proppant and soluble material to begin to bridge off 60.
In yet another exemplary embodiment, in order to promote the bridging off of the ultra lightweight proppant and soluble material, an ultra lightweight proppant may be selected having a larger diameter than the diameter of the proppant 30 used in the io fracturing fluid. The larger diameter of the ultra lightweight proppant further prevents the entrance of the ultra lightweight proppant into the fractures 40 promoting the ultra lightweight proppant to bridge off 60 against itself. The use of larger diameter ultra lightweight proppants is made possible because they can be suspended just as easily as the smaller diameter sized material unlike conventional heavier weight proppants where large sized proppants settle much more quickly.
Referring to Figure 4, as the displacement fluid 25 is slowly pumped (or displaced via the short pumping burst), the ultra lightweight proppant and soluble material continues to bridge off until a plug 70 is built up in the wellbore. The displacement fluid is continued to be pumped into the wellbore, which results in a pressure increase 20 which can be detected by various means known in the art. Once a certain pressure increase is detected, an operator and/or other monitoring means will understand/determine this indicates the wellbore has been hydraulically isolated with the plug 70.
In an exemplary embodiment, the carrier fluid utilized in fluid pill 50 is selected based upon the soluble material utilized so that the soluble material will not be prematurely dissolved. For example, if a water soluble material is used in fluid pill 50, water is not used as the carrier fluid. To do so may prematurely dissolve the soluble material in fluid pill 50 or in plug 70 after it has been created. In yet another example, oil would not be utilized as a carrier fluid for pill 50 if an oil soluble material is utilized.
Those ordinarily skilled in the art having the benefit of this disclosure realize there are a variety of carrier fluids, such as brines, which could be utilized to avoid prematurely dissolving plug 70.
In yet another exemplary embodiment, the displacement fluid 25 utilized to displace fluid pill 50 is also selected based upon the soluble material in order to avoid prematurely dissolving the soluble material. For example, if water soluble material is is used in fluid pill 50, water would not be utilized as displacement fluid 25. To do so may result in prematurely dissolving the water soluble material of fluid pill 50 before plug 70 can be created (or may prematurely dissolve plug 70). In the alternative embodiment, the same fluid is used as both the carrier and displacement fluid 25.
Further referring to the exemplary embodiment of FIG. 4, once plug 70 has been created, the zone is isolated. In accordance with the present invention, removal of plug 70 may be achieved via formation fluids or fluid introduced into the wellbore.
These fluids will dissolve plug 70 completely or dissolve plug 70 enough to allow removal of plug 70. For example, if water soluble material was utilized, the soluble material in plug 70 may be dissolved over time by water produced out of the formation. In the event an oil soluble material is utilized, the soluble material in plug 70 may be dissolved over time by production fluids. In some wells, once the soluble material has dissolved, the remaining lightweight proppant may simply flow out of the wellbore as a result of the downhole pressures, or may not inhibit production, thereby alleviating the need for a clean out of the ultra lightweight proppant and other solids, such as fracturing proppant, if utilized.
In the event clean out is required, such as a coiled tubing cleanout, fluids will be introduced into the well which will dissolve the plug 70. In either event, the use of soluble material will make the clean out quick and efficient, as well as eliminate the majority of solids disposed at the surface. Those ordinarily skilled in this art having the benefit of this disclosure realize there are a variety of clean out methods which may be utilized with the present invention. Moreover, those ordinarily skilled in the art having the benefit of this disclosure realize the time required to dissolve the soluble material is based upon a number of factors, such as well conditions, and that such time periods can be determined based upon known methods.
An exemplary method of the present invention includes a method for utilizing an isolation plug in a horizontal wellbore, the method comprising the steps of pumping a fluid pill into the horizontal wellbore, the fluid pill comprising ultra lightweight proppant and soluble material, the ultra lightweight proppant being capable of remaining suspended in the fluid pill; pumping a displacement fluid down the wellbore to displace the fluid pill; varying a pumping rate of the displacement fluid such that at least one fracture in a zone of the horizontal wellbore is allowed to at least partially close, the ultra lightweight proppant remaining suspended within the fluid pill; pumping the displacement fluid down the horizontal wellbore to slowly displace the fluid pill after the at least one fracture in the zone has at least partially closed; at least partially preventing the ultra lightweight proppant from entering the at least one fracture in the zone, wherein the ultra lightweight proppant and soluble material bridges off forming a plug within the wellbore; and subsequently removing the plug from the wellbore.
In yet another exemplary method, the soluble material comprises a water, acid, gas, or oil soluble material. The soluble material may also comprise a combination of two or more soluble materials. In yet another method, the step of removing the plug is accomplished by at least partially dissolving the soluble material in the plug. In another exemplary method, the step of at least partially dissolving the soluble material is achieved through the use of fluids being produced out of a formation. In the alternative, the step of at least partially dissolving the soluble material is achieved through the use of fluids being introduced into the wellbore from a surface location.
In yet another exemplary method, the soluble material in the plug is at least partially dissolved without performing a cleanout of the wellbore. In another method, the step of removing the plug from the wellbore is achieved by the steps of at least partially dissolving the soluble material in the plug; and removing the ultra lightweight proppant using fluids introduced into the wellbore from a surface location. In yet another exemplary method, the method further comprises the step of selecting at least one of a carrier fluid for the fluid pill or a displacement fluid for the fluid pill which would not prematurely dissolve the soluble material.
Yet another exemplary method of the present invention provides a method for utilizing an isolation plug in a horizontal wellbore, the method comprising the steps of suspending ultra lightweight proppant within a fluid pill, the fluid pill also comprising soluble material; displacing the fluid pill down the horizontal wellbore;
allowing at least one fracture in a zone of the horizontal wellbore to at least partially close;
slowing a displacement rate of the fluid pill after the at least one fracture in the zone has at least partially closed; at least partially preventing the ultra lightweight proppant from entering the at least one fracture in the zone, wherein the ultra lightweight proppant and soluble material bridges off forming a plug within the wellbore; and removing the plug.
In yet another method, the step of removing the plug is accomplished by at least partially dissolving the soluble material in the plug. In another exemplary method, the step of removing the plug is achieved without performing a cleanout of the wellbore. In the alternative, the step of removing the plug is achieved by the steps of at least partially dissolving the soluble material in the plug and removing the ultra lightweight proppant using fluids introduced into the wellbore from a surface location.
Yet another exemplary method of the present invention provides a method of using an ultra lightweight proppant and soluble material in forming a plug within a horizontal wellbore, the method comprising the steps of suspending ultra lightweight proppant within a fluid pill, the ultra lightweight proppant capable of remaining suspended while fluid pill is pumped through the horizontal wellbore, the fluid pill also comprising soluble material; pumping the fluid pill to a location adjacent a zone in the wellbore, and plugging the zone by forming a plug using the ultra lightweight proppant and soluble material, whereby the plug can be removed by at least partially dissolving the soluble material.
Yet another exemplary method further comprises the step of unplugging the zone by at least partially dissolving the soluble material using fluids being produced from the wellbore. Yet another exemplary method comprises the step of unplugging the zone by at least partially dissolving the soluble material using fluids communicated from a surface location. Another method may further comprise the step of unplugging the zone by at least partially dissolving the plug without performing a cleanout of the wellbore. Yet another method further comprises the step of selecting at least one of a carrier fluid for the fluid pill or a displacement fluid for the fluid pill which would not prematurely dissolve the soluble material. In yet another exemplary method, the carrier and displacement fluids are the same fluids.
An exemplary embodiment of the present invention provides an isolation plug for use in a horizontal wellbore, the plug comprising ultra lightweight proppant adapted to remain suspended in a fluid pill used to form the plug; and soluble material, wherein the plug is adapted to be removed by at least partially dissolving the soluble material. In another exemplary embodiment, the soluble material comprises at least one of an oil, water, gas or acid soluble material. In yet another exemplary embodiment, the soluble material in the plug is adapted to be at least partially dissolved without requiring a clean out of the horizontal wellbore. In another embodiment, the soluble material in the plug is adapted to be at least partially dissolved by fluids being produced out of a formation. In yet another exemplary embodiment, the soluble material in the plug is adapted to be at least partially dissolved by fluids being introduced into the horizontal wellbore.
Although various embodiments have been shown and described, the invention is not so limited and will be understood to include all such modifications and variations as would be apparent to one skilled in the art. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.
Claims (24)
1. A method for utilizing an isolation plug in a horizontal wellbore, the method comprising the steps of:
(a) pumping a fluid pill into the horizontal wellbore, the fluid pill comprising ultra lightweight proppant and soluble material, the ultra lightweight proppant being capable of remaining suspended in the fluid pill;
(b) pumping a displacement fluid down the wellbore to displace the fluid pill;
(c) varying a pumping rate of the displacement fluid such that at least one fracture in a zone of the horizontal wellbore is allowed to at least partially close, the ultra lightweight proppant remaining suspended within the fluid pill;
(d) pumping the displacement fluid down the horizontal wellbore to slowly displace the fluid pill after the at least one fracture in the zone has at least partially closed;
(e) at least partially preventing the ultra lightweight proppant from entering the at least one fracture in the zone, wherein the ultra lightweight proppant and soluble material bridges off forming a plug within the wellbore; and (f) subsequently removing the plug from the wellbore.
(a) pumping a fluid pill into the horizontal wellbore, the fluid pill comprising ultra lightweight proppant and soluble material, the ultra lightweight proppant being capable of remaining suspended in the fluid pill;
(b) pumping a displacement fluid down the wellbore to displace the fluid pill;
(c) varying a pumping rate of the displacement fluid such that at least one fracture in a zone of the horizontal wellbore is allowed to at least partially close, the ultra lightweight proppant remaining suspended within the fluid pill;
(d) pumping the displacement fluid down the horizontal wellbore to slowly displace the fluid pill after the at least one fracture in the zone has at least partially closed;
(e) at least partially preventing the ultra lightweight proppant from entering the at least one fracture in the zone, wherein the ultra lightweight proppant and soluble material bridges off forming a plug within the wellbore; and (f) subsequently removing the plug from the wellbore.
2. A method as defined in claim 1, wherein the soluble material comprises a water, acid, gas, or oil soluble material.
3. A method as defined in claim 1, wherein the soluble material comprises a combination of two or more soluble materials.
4. A method as defined in claim 1, wherein step (f) is accomplished by at least partially dissolving the soluble material in the plug.
5. A method as defined in claim 4, wherein the step of at least partially dissolving the soluble material is achieved through the use of fluids being produced out of a formation.
6. A method as defined in claim 4, wherein the step of at least partially dissolving the soluble material is achieved through the use of fluids being introduced into the wellbore from a surface location.
7. A method as defined in claim 4, wherein the soluble material in the plug is at least partially dissolved without performing a cleanout of the wellbore.
8. A method as defined in claim 1, wherein step (f) is achieved by the steps of:
at least partially dissolving the soluble material in the plug; and removing the ultra lightweight proppant using fluids introduced into the wellbore from a surface location.
at least partially dissolving the soluble material in the plug; and removing the ultra lightweight proppant using fluids introduced into the wellbore from a surface location.
9. A method as defined in claim 4, the method further comprising the step of selecting at least one of a carrier fluid for the fluid pill or a displacement fluid for the fluid pill which would not prematurely dissolve the soluble material.
10. A method for utilizing an isolation plug in a horizontal wellbore, the method comprising the steps of:
(a) suspending ultra lightweight proppant within a fluid pill, the fluid pill also comprising soluble material;
(b) displacing the fluid pill down the horizontal wellbore;
(c) allowing at least one fracture in a zone of the horizontal wellbore to at least partially close;
(d) slowing a displacement rate of the fluid pill after the at least one fracture in the zone has at least partially closed;
(e) at least partially preventing the ultra lightweight proppant from entering the at least one fracture in the zone, wherein the ultra lightweight proppant and soluble material bridges off forming a plug within the wellbore; and (f) removing the plug.
(a) suspending ultra lightweight proppant within a fluid pill, the fluid pill also comprising soluble material;
(b) displacing the fluid pill down the horizontal wellbore;
(c) allowing at least one fracture in a zone of the horizontal wellbore to at least partially close;
(d) slowing a displacement rate of the fluid pill after the at least one fracture in the zone has at least partially closed;
(e) at least partially preventing the ultra lightweight proppant from entering the at least one fracture in the zone, wherein the ultra lightweight proppant and soluble material bridges off forming a plug within the wellbore; and (f) removing the plug.
11. A method as defined in claim 10, wherein step (f) is accomplished by at least partially dissolving the soluble material in the plug.
12. A method as defined in claim 11, wherein step (f) is achieved without performing a cleanout of the wellbore.
13. A method as defined in claim 10, wherein step (f) is achieved by the steps of:
at least partially dissolving the soluble material in the plug; and removing the ultra lightweight proppant using fluids introduced into the wellbore from a surface location.
at least partially dissolving the soluble material in the plug; and removing the ultra lightweight proppant using fluids introduced into the wellbore from a surface location.
14. A method of using an ultra lightweight proppant and soluble material in forming an isolation plug within a horizontal wellbore, the method comprising the steps of:
(a) suspending ultra lightweight proppant within a fluid pill, the ultra lightweight proppant capable of remaining suspended while fluid pill is pumped through the horizontal wellbore, the fluid pill also comprising soluble material;
(b) pumping the fluid pill to a location adjacent a zone in the wellbore, and (c) plugging the zone by forming a plug using the ultra lightweight proppant and soluble material, whereby the plug can be removed by at least partially dissolving the soluble material.
(a) suspending ultra lightweight proppant within a fluid pill, the ultra lightweight proppant capable of remaining suspended while fluid pill is pumped through the horizontal wellbore, the fluid pill also comprising soluble material;
(b) pumping the fluid pill to a location adjacent a zone in the wellbore, and (c) plugging the zone by forming a plug using the ultra lightweight proppant and soluble material, whereby the plug can be removed by at least partially dissolving the soluble material.
15. A method as defined in claim 14, the method further comprising the step of unplugging the zone by at least partially dissolving the soluble material using fluids being produced from the wellbore.
16. A method as defined in claim 14, the method further comprising the step of unplugging the zone by at least partially dissolving the soluble material using fluids communicated from a surface location.
17. A method as defined in claim 14, the method further comprising the step of unplugging the zone by at least partially dissolving the plug without performing a cleanout of the wellbore.
18. A method as defined in claim 14, the method further comprising the step of selecting at least one of a carrier fluid for the fluid pill or a displacement fluid for the fluid pill which would not prematurely dissolve the soluble material.
19. A method as defined in claim 18, wherein the carrier and displacement fluids are the same fluids.
20. An isolation plug for use in a horizontal wellbore, the plug comprising:
ultra lightweight proppant adapted to remain suspended in a fluid pill used to form the plug; and soluble material, wherein the plug is adapted to be removed by at least partially dissolving the soluble material.
ultra lightweight proppant adapted to remain suspended in a fluid pill used to form the plug; and soluble material, wherein the plug is adapted to be removed by at least partially dissolving the soluble material.
21. An isolation plug as defined in claim 20, wherein the soluble material comprises at least one of an oil, water, gas or acid soluble material.
22. An isolation plug as defined in claim 20, wherein the soluble material in the plug is adapted to be at least partially dissolved without requiring a clean out of the horizontal wellbore.
23. An isolation plug as defined in claim 20, wherein the soluble material in the plug is adapted to be at least partially dissolved by fluids being produced out of a formation.
24. An isolation plug as defined in claim 20, wherein the soluble material in the plug is adapted to be at least partially dissolved by fluids being introduced into the horizontal wellbore.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2658472A CA2658472C (en) | 2009-03-13 | 2009-03-13 | Plug and related methods for isolating open perforations in horizontal wellbores using ultra lightweight proppant and soluble material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2658472A CA2658472C (en) | 2009-03-13 | 2009-03-13 | Plug and related methods for isolating open perforations in horizontal wellbores using ultra lightweight proppant and soluble material |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2658472A1 CA2658472A1 (en) | 2010-09-13 |
| CA2658472C true CA2658472C (en) | 2012-06-26 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2658472A Expired - Fee Related CA2658472C (en) | 2009-03-13 | 2009-03-13 | Plug and related methods for isolating open perforations in horizontal wellbores using ultra lightweight proppant and soluble material |
Country Status (1)
| Country | Link |
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| CA (1) | CA2658472C (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112647892A (en) * | 2020-12-28 | 2021-04-13 | 黑龙江弘力通能源技术服务有限公司 | Method for temporarily blocking large-scale underground fracturing hole |
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- 2009-03-13 CA CA2658472A patent/CA2658472C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| CA2658472A1 (en) | 2010-09-13 |
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