Exxon Production Research Company

Steven R Erbstoesser

Claude E Cooke, Jr

Richard G Sinclair

Michael M Epstein

Robert L Graham

Charles O Stokley

Thomas W Muecke

Christopher M Shaughnessy

Gerard A Gabriel

An improved method for placing ball sealers (25) onto casing perforations (17) in a deviated wellbore (10) is disclosed. In this invention, a plurality of ball sealers (25) are introduced into the casing and are transported to the perforations at an interface (26) between two immiscible fluids; the first or leading fluid (21) having a density greater than the ball sealers and the second or trailing fluid (24) having a density greater than the ball sealers.

Method for placing ball sealers onto casing perforations in a deviated

Plugging perforations in casing in a wellbore penetrating a subterranean formation using degradale ball sealers. The ball sealer used is composed of a polyester polymer which is substantially insoluble in the wellbore fluid. The polymer degrades in the presence of water at an elevated temperature to form small molecules which are soluble in a fluid in the subterranean formation. After the polymer degrades, the flow through the perforation returns to substantially its initial value.

Use of degradable ball sealers to seal casing perforations in well

The present invention relates generally to the composition and method for reducing the permeability of subterranean formations penetrated by a wellbore. The composition of the present invention comprises a wellbore fluid having dispersed therein a fluid loss control agent comprising a polyester polymer which is substantially insoluble in the wellbore fluid. The polymer degrades in the presence of water at an elevated temperature to form small molecules which are soluble in a fluid in the subterranean formation. The method of the present invention comprises reducing the permeability of subterranean formations penetrated by a wellbore by placing the composition of the present invention down the wellbore.

Composition for reducing the permeability of subterranean formations

A method of preventing overdisplacement and underdisplacement of proppant during well treatments to hydraulically induce and maintain a fracture in a subterranean formation traversed by a wellbore having a perforated casing. In the practice of the method, ball sealers are incorporated in the trailing end portion of a fracturing fluid-proppant slurry. The ball sealers have a density such that they do not sink in the slurry nor rise in the displacement fluid injected following the slurry. The ball sealers seat on at least some of the well perforations as the final portion of the slurry reaches the perforations. This causes the surface pumping pressure to increase, signalling the end of the treating operation. The detection of the time at which a selected portion of the injected fluid reaches the perforations allows the treatment to be terminated, minimizing proppant overdisplacement and providing for a fully packed fracture in the near-wellbore region. In another embodiment of the method, slurries of different densities are utilized, with the ball sealers having a density such that they remain at the interface between the slurries during the injection process.

Method of controlling displacement of propping agent in fracturing

A method of preventing overdisplacement of propping agent particles during well treatments to hydraulically induce a fracture in a subterranean formation wherein buoyant or neutrally buoyant ball sealers are incorporated in the trailing end portion of the fracturing fluid. The ball sealers seat on at least some of the well perforations in final stages of particle injection thereby causing the surface pumping pressure to increase, signalling the end of the treating operation. This minimizes proppant overdisplacement and provides for a fully packed fracture in the near wellbore region.

Ball sealers comprising a solid core coated with a polyurethane elastomer are introduced into a well to seal well perforations and divert fluid therein. In the preferred embodiment the ball sealers are used in a hydrocarbon liquid treating fluid and have a density less than the treating fluid.

Polyurethane ball sealers for well treatment fluid diversion

Method for reducing the permeability of subterranean formations

There is disclosed a method for selective diversion in a deviated wellbore comprising generally perforating the casing with a first group of perforations at the top or bottom abutting an imaginary plane which is substantially in the vertical and extends along the longitudinal axis of the casing and perforating the casing with a second group of perforations circumferentially spaced-away from the plane. Diversion is accomplished by injecting buoyant or non-buoyant diverting agents into the casing and transporting them down the casing in a pathway adjacent to the casing and the imaginary plane. The diverting agents bypass the circumferentially spaced-away perforations and seat in at the perforations at the top or bottom of the casing.

Method of selective diversion in deviated wellbores using ball sealers

A ball sealer for use as a diverting agent when treating a well having a perforated casing. The ball sealer is sized to plug a perforation and has a density less than the treating fluid. The ball sealer comprises a material, such as syntactic foam or polymethylpentene. The ball sealer is also preferably provided with a protective covering material. After some of the treating fluid has been injected into the well, the ball sealers are injected and carried by the fluid flow down to the perforations where they seat and divert the further injection of treating fluid through the remaining open perforations.

Low density ball sealers for use in well treatment fluid diversions

A method is disclosed for transporting ball sealers down a perforated casing of a well to affect fluid diversion when hydraulically treating a formation penetrated by the well. In this invention, ball sealers are transported to said perforations in a carrier fluid system comprising a leading fluid portion having a density greater than said ball sealers and a trailing fluid portion having a density less than said ball sealers. The ball sealers will be moved downwardly in the casing to the perforations and will seat onto the perforations through which fluids are flowing to divert fluid through the unplugged perforations.

Method for placing ball sealers onto casing perforations

An apparatus and method for the selective placement of ball sealers for fluid treatment of a well, said ball sealers having a density less than the density of said fluid comprising a tubular member, means on said tubular member for positioning said apparatus in said well casing and means on said tubular member for deploying and blocking said well casing to prevent upward movement of said ball sealers past said apparatus.

Placement apparatus and method for low density ball sealers

A method and apparatus are described for diverting fluid when treating a subterranean formation penetrated by a well provided with casing having a plurality of perforations. Ball sealers having a density less than fluid in the casing are lowered down the casing between upper perforations and lower perforations. A screen means is positioned above the ball sealers to prevent upward migration of the balls to a level adjacent the upper perforations. A preferred screen means comprises a cage which is open at its lower end and has openings in its upper end which prevent passage of ball sealers therethrough and permits fluid flow down the casing and through the cage. The cage with the ball sealers therein is lowered down the casing by a conventional wireline. Once the cage and ball sealers are between the upper and lower perforations, a treating fluid more dense than the ball sealers is injected into the well to cause fluid flow. The treating fluid is caused to flow through the screen means to carry the ball sealers down the casing to plug the lower perforations while leaving the upper perforations open to fluid flow.

Method and apparatus for placing buoyant ball sealers

A method for sequential treatment of formation strats when treating fluid is pumped into a well at a matrix rate by temporarily closing perforations in the well casing. The perforations are closed by ball sealers injected into the wall during the treatment. The ball sealers are sized to plug the perforations and have a density less than the density of the treating fluid. The treating fluid is injected at a rate which transports the ball sealers to the perforations but which is sufficiently low to prevent formation fracture.

Ball sealer diversion of matrix rate treatments of a well

A ball sealer for use as a diverting agent when treating a well having a perforated casing. The ball sealer is sized to plug a perforation and has a density less than the treating fluid. The ball sealer is made of a core material, such as syntactic foam or polymethylpentene, and a covering of a thin layer of an elastomeric material. After some of the treating fluid has been injected into the well, the ball sealers are injected and carried by the fluid flow down to the perforations where they seat and divert the further injection of treating fluid through the remaining open perforations.

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Missouri City, TX, United States of America

Steven R Erbstoesser