Wells – Processes – Material placed in pores of formation to treat resident...
Reexamination Certificate
2002-10-16
2004-08-17
Schoepper, Roger (Department: 3672)
Wells
Processes
Material placed in pores of formation to treat resident...
C166S280200, C166S308100, C166S281000, C166S295000, C166S293000
Reexamination Certificate
active
06776236
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods of completing unconsolidated hydrocarbon producing zones whereby proppant particles and formation solids do not flow-back with produced hydrocarbons.
2. Description of the Prior Art
Hydrocarbon producing wells are often completed in unconsolidated formations containing loose and incompetent particulate solids, e.g., sand, which migrate with hydrocarbons and/or water produced by the wells. The presence of the particulate solids in the produced fluids is highly undesirable in that the solid particles abrade tubular goods, pumping equipment, valves and other producing equipment and reduce the fluid production capabilities of the producing zone in the wells. Incompetent subterranean formations include those which contain loose particulate solids that are readily entrained by produced fluids and those wherein the particulate solids making up the formations are bonded together with insufficient bond strength to withstand the forces produced by the production of fluids from the formations.
A technique which is often used for minimizing particulate solid production from unconsolidated formations has been to produce fluids from the formations at low flow rates whereby the near well stabilities of particulate solid bridges and the like in the formations are preserved. However, the collapse of such particulate solid bridges often occurs as a result of unintentional high production rates and/or pressure cycling. Pressure cycling occurs from frequent shut-ins and start-ups of a well. The frequency of the pressure cycling is very critical to the longevity of the near well formation, especially during the depletion stage of the well when the pore pressure of the formation has already been significantly reduced.
Heretofore, unconsolidated formations have been treated by creating fractures in the formations and depositing proppant in the fractures to maintain them in open positions. In addition, the proppant has heretofore been consolidated within the fractures into hard permeable masses by hardenable resin compositions to reduce the migration of particulate solids through the fractures with produced fluids. Very often, to insure that particulate solids are not produced, costly gravel packs, sand screens and the like have also been installed in the wells. Since gravel packs and sand screens filter out particulate solids from the fluids being produced, the presence of the filtered particulate solids adds to the flow resistance thereby producing additional pressure draw-down which causes the fracture faces and other portions of the unconsolidated formations to break down and the consolidated proppant in fractures, gravel packs and the like to be bypassed. In addition, pressure cycling often causes the consolidated proppant particles within the fractures to break down whereby proppant particle flow-back with produced fluids occurs.
Thus, there is a need for improved methods of completing wells in unconsolidated formations whereby the migration of formation particulate solids and proppant particle flow-back with produced fluids are prevented.
SUMMARY OF THE INVENTION
The present invention provides improved methods of completing an unconsolidated hydrocarbon producing zone penetrated by a well bore having casing cemented therein, the producing zone having a temperature above about 200° F. A method of the invention is comprised of the following steps. Spaced openings are formed through the casing and cement into the unconsolidated producing zone. A first hardenable resin composition is then injected into the unconsolidated producing zone adjacent to the well bore. Without waiting for the first hardenable resin composition to harden, a hydraulic fracturing treatment fluid containing proppant particles coated with a second hardenable resin composition is injected through the openings into the unconsolidated producing zone at a rate and pressure sufficient to fracture the producing zone. The proppant particles coated with the second hardenable resin composition are caused to be deposited in the fracture. The first hardenable resin composition and the second hardenable resin composition are then allowed to harden by heat whereby the unconsolidated producing zone adjacent to the well bore and the proppant particles in the fractures are consolidated into hard permeable masses so that proppant particles and formation solids are prevented from flowing out of the producing zone with produced hydrocarbons.
The objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides improved methods of completing an unconsolidated hydrocarbon producing zone having a temperature above about 200° F. penetrated by a well bore having casing cemented therein. The methods are basically comprised of the following steps. Spaced openings are formed through the casing and cement into the unconsolidated producing zone. A first hardenable resin composition is injected through the openings into the unconsolidated producing zone adjacent to the well bore and at least a portion of the resin composition is optionally displaced from the pore spaces of the producing zone by an aqueous salt solution. Without waiting for the first hardenable resin composition injected into the producing zone to harden, a fracturing fluid containing proppant particles coated with a second hardenable resin composition is injected through the openings into the unconsolidated producing zone at a rate and pressure sufficient to fracture the producing zone. The proppant particles coated with the second hardenable resin composition are then caused to be deposited in the fractures. Thereafter, the first hardenable resin composition and the second hardenable resin composition are allowed to harden by heat whereby the unconsolidated producing zone adjacent to the well bore and the proppant particles in the fractures are consolidated into hard permeable masses so that the proppant particles and formation solids are prevented from flowing out of the producing zone with produced hydrocarbons.
The spaced openings in the casing and cement are preferably formed on opposite sides of the casing and cement in directions parallel with the maximum horizontal stress in the subterranean zone. This causes opposing vertical fractures to be formed in the unconsolidated producing zone, sometimes referred to in the art as “by-wing” fractures. The openings through the casing and cement are spaced longitudinally on the opposite sides of the casing utilizing well known perforating or hydrojetting techniques to produce perforations or slots in the casing and cement.
The first hardenable resin composition which is injected through the openings in the casing and cement into the unconsolidated producing zone adjacent to the well bore is comprised of a furfuryl alcohol resin, furfuryl alcohol, a solvent for the furfuryl alcohol resin and a silane coupling agent to enhance the bonding of the resin to the particulate solids in the producing zone. The first hardenable resin composition can optionally also include a benzalkonium chloride cationic surfactant for enhancing the compatibility between the formation particulate solids and the salt solution used to displace the resin composition from the pore spaces of the producing zone.
Furfuryl alcohol resins are readily available from a number of commercial sources. For example, suitable furfuryl alcohol resin is commercially available from The Durez Corporation under the trade designation “DUREZ 33682™”. Upon curing by heat in a subterranean zone, the furfuryl alcohol resin forms an insoluble mass that is highly resistant to chemical attack and thermal degradation, i.e., the cured resin resists thermal degradation at temperatures up to 700° F. The furfuryl alcohol resin is generally present in the first hardenable resin composition in an amount in the range of from a
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Schoepper Roger
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