Wells – Processes – Separate steps of fracturing or attacking formation
Reexamination Certificate
2002-08-28
2004-03-16
Walker, Zakiya (Department: 3672)
Wells
Processes
Separate steps of fracturing or attacking formation
C166S280100, C166S295000, C166S308400, C523S131000, C507S219000, C507S220000, C507S221000, C507S231000, C507S239000, C507S922000, C507S924000
Reexamination Certificate
active
06705400
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved methods of forming fractures containing resilient proppant particle packs which prevent proppant flow-back in subterranean zones penetrated by well bores.
2. Description of the Prior Art
Hydrocarbon producing wells are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a viscous fracturing fluid which also functions as a carrier fluid is pumped into a producing zone to be fractured at a rate and pressure such that one or more fractures are formed in the zone. Particulate proppant particles, e.g., graded sand for propping the fractures are suspended in a portion of the fracturing fluid so that the proppant particles are deposited in the fractures when the fracturing fluid is broken. That is, a breaker is included in the fracturing fluid whereby the fracturing fluid reverts to a thin fluid which is returned to the surface. The proppant particle packs formed in the fractures function to prevent the fractures from closing so that conductive channels are formed through which produced hydrocarbons can readily flow.
In order to prevent the subsequent flow-back of the proppant particles as well as loose or incompetent sand in the fractured zone with fluids produced therefrom, the proppant introduced into the fractures has heretofore been coated with a hardenable resin composition which is caused to harden and consolidate the proppant particles in the zone. The flow-back of the proppant particles with formation fluids is very detrimental in that it erodes metal goods, plugs piping and vessels and causes damage to valves, instruments and other production equipment.
While the consolidated proppant particle packs heretofore formed in subterranean fractures have functioned satisfactorily in wells which are produced continuously, when such consolidated proppant particle packs are formed in wells which are frequently placed on production and then shut-in, flow-back of the proppant particles and formation fines with produced fluids often still takes place. That is, in wells which are subjected to stress cycling due to frequent opening and shutting in of the wells, the consolidated proppant particle packs in fractures are also subjected to the stress cycling which causes the consolidated proppant particle packs to disintegrate and the flow-back of loose proppant particles to occur. Thus, there are needs for improved methods of forming proppant particle packs in subterranean fractures which are resilient and do not disintegrate when subjected to stress cycling.
SUMMARY OF THE INVENTION
The present invention provides improved methods and compositions for forming subterranean fractures containing resilient proppant particle packs which meet the needs described above and overcome the deficiencies of the prior art. The resin compositions of this invention harden and consolidate resin coated proppant particles into resilient permeable packs which do not allow proppant flow-back.
The methods of this invention are basically comprised of the following steps. A liquid hardenable resin component is provided comprised of a hardenable resin and optionally, a solvent for the resin. A liquid hardening agent component is provided comprised of a hardening agent, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier fluid having a high flash point and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid. A liquid rubber component comprised of a rubber latex and a rubber latex stabilizing surfactant is also provided. In addition, a source of dry proppant particles and a gelled liquid fracturing fluid are provided. The gelled liquid fracturing fluid is pumped into a subterranean zone to form the fractures therein and to place hardenable resin composition coated proppant particles therein. As the fractures are formed by the fracturing fluid, the liquid hardenable resin component is mixed with the liquid hardening agent component and the liquid rubber component (preferably on-the-fly) to form a liquid hardenable resin composition. The liquid hardenable resin composition is continuously coated on dry proppant particles conveyed from the source thereof to form hardenable resin composition coated proppant particles. The hardenable resin coated proppant particles are continuously mixed with the fracturing fluid whereby the hardenable resin composition coated proppant particles are suspended in the fracturing fluid. When the hardenable resin composition coated proppant particles have been placed in the one or more fractures, the pumping of the fracturing fluid, the mixing of the liquid hardenable resin component with the liquid hardening agent component and the liquid rubber component, the coating of the dry proppant particles with the hardenable resin composition and the mixing and suspending the resin composition coated proppant particles with the fracturing fluid are terminated. Thereafter, the hardenable resin composition on the coated proppant particles is allowed to harden and to consolidate the proppant into one or more strong and resilient permeable packs which prevent the production of formation sand and fines with formation fluids and proppant flow-back.
The liquid hardenable resin composition of this invention for consolidating proppant particles in subterranean fractures whereby consolidated proppant particle packs are formed which are resilient and prevent proppant particle flow-back due to stress cycling is comprised of the following components: a hardenable resin, optionally a solvent for the resin, a hardening agent for hardening the resin, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing films on the proppant particles, a surfactant for facilitating the coating of the resin on the proppant particles and for causing the hardenable resin to flow to the contact points between adjacent resin coated proppant particles, a liquid carrier fluid having a high flash point and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid, a rubber latex and a rubber latex stabilizing surfactant.
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
As mentioned above, the consolidated proppant particle packs formed in fractures heretofore have not been resilient enough to remain consolidated in wells which are frequently placed on production and shut-in. That is, the stress cycling caused by frequently producing and shutting in wells causes the consolidated proppant particle packs to disintegrate over time which causes undesirable proppant particle flow-back.
In accordance with the methods and compositions of the present invention, the resin consolidated proppant particle packs formed in subterranean fractures are highly resilient whereby they can withstand stress cycling without disintegration occurring.
The methods of the present invention for forming fractures containing resilient proppant particle packs which prevent the production of formation sand and fines with formation fluids and proppant flow-back in subterranean zones penetrated by well bores are comprised of the following steps. A liquid hardenable resin component is provided comprised of a hardenable resin, and optionally, a solvent for the resin having a high flash point. A liquid hardening agent component is also provided comprised of a hardening agent, a silane coupling agent, a hydrolyzable ester for breaking gelled fracturing fluid films on the proppant particles
Barton Johnny A.
Nguyen Philip D.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Walker Zakiya
LandOfFree
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