1. Field of the Disclosure
The embodiments described herein relate to a system and method for re-fracturing select locations, such as prior perforations, prior fractures, and/or prior fracture clusters, of the formation of a multizone horizontal wellbore. The formation may also re-fracture the formation through a sliding sleeve left open during a prior hydraulic fracturing process.
2. Description of the Related Art
Natural resources such as gas and oil may be recovered from subterranean formations using well-known techniques. For example, a horizontal wellbore may be drilled within the subterranean formation. After formation of the horizontal wellbore, a string of pipe, e.g., casing, may be run or cemented into the well bore. Hydrocarbons may then be produced from the horizontal wellbore.
In an attempt to increase the production of hydrocarbons from the wellbore, the casing may be perforated and fracturing fluid may be pumped into the wellbore to fracture the subterranean formation. The fracturing fluid is pumped into the well bore at a rate and a pressure sufficient to form fractures that extend into the subterranean formation, providing additional pathways through which fluids being produced can flow into the well bores. The fracturing fluid typically includes particulate matter known as a proppant, e.g., graded sand, bauxite, or resin coated sand, may be suspended in the fracturing fluid. The proppant becomes deposited into the fractures and thus holds the fractures open after the pressure exerted on the fracturing fluid has been released.
Another method to increase the production of hydrocarbons from a wellbore is to attempt to fracture the formation through ported collars or tubulars within the wellbore. Typically, these ported collars may be selectively closed by a sliding sleeve, which may be actuated to an open position by various means such as by the use of a shifting tool or by the application of a pressure differential. Once the port is opened, fracturing fluid may be pumped down the well and out the port in an attempt to fracture the formation to increase production of hydrocarbons.
A production zone within a wellbore may have been previously fractured, but the prior fracturing may not have adequately fractured the formation leading to inadequate production from the production zone. Even if the formation was adequately fractured, the production zone may no longer be producing at adequate levels. Over an extended period of time, the production from a previously fractured horizontal wellbore may decrease below a minimum threshold level. One technique in attempting to increase the hydrocarbon production from the wellbore is the addition of new fractures within the subterranean formation. One potential problem in introducing new fractures in the formation is that fracturing fluid pumped into the wellbore may enter prior fractures formed in the subterranean formation instead of creating new fractures. Expandable tubulars or cladding procedures have been used within a wellbore in an attempt to block the flow path of the fracturing fluid to the old fractures, instead promote the formation of new fracture clusters. The use of expandable tubulars or cladding may not adequately provide the desired results and further, may incur too much expense in the effort to increase products from the wellbore. A more efficient way to increase the production of a horizontal wellbore is needed.
The present disclosure is directed to a method and system for re-fracturing select locations of a formation in a multizone horizontal wellbore that have been previously fractured or were attempted to be fractured that overcomes some of the problems and disadvantages discussed above.
One embodiment is a method for re-fracturing a location of a formation of a multizone horizontal wellbore comprising hydraulically isolation a first location from a portion of the multizone wellbore uphole from the first location, the first location having been previously hydraulically fractured at least once and hydraulically re-fracturing the first location. The method comprises providing a first diverting material proximate to the first location after the first location has been hydraulically re-fractured, wherein the first diverting material hydraulically isolates the re-fractured first location from the multizone horizontal wellbore uphole of the first location. The method comprises hydraulically isolating a second location from a portion of the multizone horizontal wellbore uphole of the second location, the second location having been previously hydraulically fractured at least once and hydraulically re-fracturing the second location. The method comprises providing a second diverting material proximate to the second location after the second location has been re-fractured, wherein the second diverting material hydraulically isolates the re-fractured second location from a portion of the multizone horizontal wellbore uphole of the second location.
The first location may be a fracture cluster farther downhole of the multizone horizontal wellbore and wherein hydraulically isolating the first location may include creating a seal with a packing element connected to a coiled tubing string to seal an annulus between the coiled tubing string and a casing of the multizone horizontal wellbore uphole of the first location. The method may include cleaning out at least a portion of the multizone horizontal wellbore prior to hydraulically isolating the first location. The method may include cleaning out at least a portion of the multizone horizontal wellbore after re-fracturing the first and second locations to remove the first and second diverting materials from the multizone horizontal wellbore. The method may include producing hydrocarbons from the re-fractured first and second locations of the multizone horizontal wellbore. The first and second diverting material may comprises one or more of a thermoset plastic, a thermoset polymer, a sand plug, disintegrating frac balls, a gel, a cross-linked gel, frac balls, dissolving material, fiber laden diversion fluid, particulates, or a bridge of degradable particles. The method may include determining whether to hydraulically re-fracture the first location prior to hydraulically re-fracturing the first location and determining whether to hydraulically re-fracture the second location prior to hydraulically re-fracturing the second location. The method may include logging the first and second locations with a logging tool. There may be at least one fracture cluster positioned between the first location and the second location. Hydraulically isolation the second location may include providing a third diverting material between the first and second locations and creating a seal with a packing element connected to a coiled tubing string to seal an annulus between the coiled tubing string and a casing of the multizone horizontal wellbore uphole from the second location, wherein the third diverting material is provided prior to creating the seal uphole from the second location.
One embodiment is a system for re-fracturing a plurality of locations within a multizone horizontal wellbore comprising a first tubing string positioned within a multizone horizontal wellbore, the first tubing string extending from a surface location to a first location in the multizone horizontal wellbore. The first location being a lowermost previously fractured location along the multizone horizontal wellbore. The system comprises a packing element connected proximate to an end of the first tubing string, the packing element adapted to repeatedly seal an annulus between the first tubing string and a casing of the multizone horizontal wellbore, the end of the first tubing string being adapted to permit the hydraulic re-fracturing of selected locations within the multizone horizontal wellbore. The system comprises a plurality of diverting material, each of the plurality of diverting material positioned proximate to a previously fractured location to selectively hydraulically isolate the previously fractured location.
The first tubing string may be a coiled tubing string. The first tubing string may be comprised of a section of rigid tubing connected to a lower end of a coiled tubing string. The system may include a testing device connected to a second tubing string, the testing device adapted to determine whether a previously fractured location should be re-fractured, wherein the second tubing string is positioned within the multizone horizontal wellbore prior to the first tubing string being positioned within the multizone horizontal wellbore. The testing device may be a logging device.
One method is a method for selectively re-fracturing one or more previously fractured locations within a wellbore comprising positioning a packing element uphole of a first previously fractured location, the packing element being connected to a tubing string and actuating the packing element to seal an annulus between the tubing string and a casing uphole of the first previously fractured location. The method comprises pumping fluid down the tubing string to re-fracture the first previously fractured location and providing a first diverting material proximate the re-fractured first previously fractured location. The method comprises unsetting the packing element and positioning the packing element uphole of a second previously fractured location. The method comprises actuating the packing element to seal the annulus between the tubing string and the casing uphole of the second previously fractured location and pumping fluid down the tubing string to re-fracture the second previously fractured location. The method comprises providing a second diverting material proximate the re-fractured second previously fractured location.
The method may include positioning a testing device proximate to the first previously fractured location and determining that the first previously fractured location should be re-fractured prior to re-fracturing the first previously fractured location and positioning the testing device proximate to the second previously fractured location and determining that the second previously fractured location should be re-fractured prior to re-fracturing the second previously fractured location. The method may include removing the first and second diverting materials and producing hydrocarbons from the re-fractured first and second previously fractured locations. The method may include determining a third previously fractured location should not be re-fractured prior to positioning the packing element uphole of the second previously fractured location, wherein the third previously fractured location is positioned between the first previously fractured location and the second previously fractured location. The method may include providing a third diverting material proximate the third previously fractured location prior to positioning the packing element uphole of the second previously fractured location.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the invention as defined by the appended claims.
For illustrative purposes only,
A production zone may have as few as a single fracture cluster or may include more than ten (10) fracture clusters. The multiple zones of a multizone horizontal wellbore 1 may include a plurality of fracture clusters 10, 20, and 30 that extend into the formation 5 that surrounds the casing 6 of the multizone horizontal wellbore 1. As discussed above, the formation 5 is fractured by a plurality of fracture clusters 10, 20, and 30 to increase the production of hydrocarbons from the wellbore. When the rate of production from the horizontal wellbore decreases below a minimum threshold value it may be necessary to re-fracture selected fracture clusters 10, 20, and 30 within the wellbore 1, as discussed below.
A tubing string 7 may be positioned within the casing 6 of the horizontal wellbore 1. Fluid may be pumped down the tubing string 7 and out the end 9 of the tubing string and reverse circulated up the annulus to clean out the horizontal wellbore 1 prior to the re-fracturing process as shown in
After the horizontal wellbore 1 has been cleaned out, a tubing string 7 may be positioned within the casing 6 of the horizontal wellbore 1 having a packer or sealing element 8, hereinafter referred to as a packer. The packer 8 may be actuated to create a seal in the annulus between the tubing string 7 and the casing. The tubing string 7 may be comprised of various tubulars that permit locating and operating a packer or sealing element, as discussed below, within the horizontal wellbore 1 and also permit the pumping of fluid down the tubing string 7 to a desired location along the horizontal wellbore 1. For example, the tubing string 7 may be coiled tubing that extends from the surface to the location of the fracture cluster 10a positioned farthest downhole of the horizontal wellbore 1. Another example is a tubing string 7 comprised of a rigid tubular section 70 connected to coiled tubing 75, as shown schematically in
The packer 8 may be positioned uphole of the lowermost fracture cluster 10a and actuated to create a seal between the tubing string 7 and the casing 6 of the horizontal wellbore 6.
The packer 8 includes a sealing element may be repeatedly actuated and/or energized to create a seal between the tubing string 7 and the wellbore casing 6. Debris within the annulus may potentially interfere with the repeated actuation of the packer 8. In an effort to minimize interference from debris within the wellbore 1, the packer 8 may include a debris exclusion device, such as one or more cups, positioned downhole from the packing element, which may help to prevent debris and/or material within the wellbore from interfering with the creation of a seal by the sealing element of the packer 8. One example of such a packing element is discussed in U.S. Pat. No. 6,315,041 to Stephen L. Carlisle and Douglas J. Lehr entitled Multi-zone Isolation Tool and Method of Stimulating and Testing a Subterranean Well, which is incorporated by reference herein in its entirety.
After the placement of diverting material 40 to isolate a re-fractured cluster 110a the tubing string 7 may be moved uphole to position the packer 8 above the next fracture cluster 10b that is to be re-fractured. As discussed below, the adjacent fracture cluster may not be the next fracture cluster to be re-fractured. Instead, a fracture cluster or multiple fracture clusters may be passed over during the re-fracturing process. Diverting material may be pumped down the tubing string 7 to isolate a passed over fracture cluster during the re-fracturing of the next fracture cluster.
The diverting material 40 placed within the horizontal wellbore 1 to hydraulically isolate sections of the horizontal wellbore needs to be removed once it is desired to produce from the hydraulically isolated clusters and/or once all of the desired fracture clusters have been re-fractured.
Although this invention has been described in terms of certain preferred embodiments, other embodiments that are apparent to those of ordinary skill in the art, including embodiments that do not provide all of the features and advantages set forth herein, are also within the scope of this invention. Accordingly, the scope of the present invention is defined only by reference to the appended claims and equivalents thereof.
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