Wells – Processes – Specific propping feature
Reexamination Certificate
2002-06-26
2004-05-04
Neuder, William (Department: 3672)
Wells
Processes
Specific propping feature
C166S281000
Reexamination Certificate
active
06729404
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved methods and compositions for consolidating proppant in subterranean fractures formed by a gelled liquid fracturing fluid.
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 solids, e.g., graded sand, for propping the fractures, commonly referred to in the art as “proppant” are suspended in a portion of the fracturing fluid so that the particulate solids 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 deposited in the fractures functions 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 proppant as well as loose or incompetent sand in the fractured zone with fluids produced therefrom, a portion of 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. Typically, the hardenable resin composition coated proppant is deposited in the fractures after a large quantity of uncoated proppant has been deposited therein. That is, the last portion of the proppant deposited in each fracture, referred to in the art as the “tail-end” portion, is coated with the hardenable resin composition. When the viscous fracturing fluid which is the carrier fluid for the proppant is broken and reverts to a thin fluid as described above, the hardenable resin coated proppant is deposited in the fractures and the fractures close on the proppant. The partially closed fractures apply pressure on the hardenable resin coated proppant particles whereby the particles are forced into contact with each other while the resin composition hardens. It has heretofore been thought that the hardening of the resin composition under pressure brings about the consolidation of the resin coated proppant particles into a hard permeable pack having sufficient compressive and tensile strength to prevent unconsolidated proppant and formation sand from flowing out of the fractures with produced fluids. However, it has been found that as the fracturing fluid containing proppant without a hardenable resin composition coating thereon is carried into the fractures by the fracturing fluid, some of the proppant is continuously deposited in the bottom of the fractures adjacent to the well bore. This unconsolidated accumulation of non-resin coated proppant remains in the fractures adjacent to the well bore and when the hardenable resin coated proppant enters the fractures at the end of the proppant deposit, it does not displace the uncoated proppant at the bottom of the fractures. Instead, the hardenable resin coated proppant flows over the uncoated proppant. This results in unconsolidated proppant at the bottom of the fractures adjacent to the well bore. During the subsequent production of formation fluids through the propped fractures, the unconsolidated proppant at the bottom of the fractures flows back with the formation fluids. The flow-back of the proppant with the 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.
Another problem encountered in the use of prior hardenable resin compositions for coating proppant particles is that the hardenable resin composition components, i.e., the liquid hardenable resin component and the liquid hardening agent component, have heretofore had very short shelf lives. That is, the shelf lives of the hardenable resin composition components have heretofore been as short as about four days or less. In addition, the hardenable resin composition components have heretofore had very low flash points, i.e., flash points of about 60° F. or below making them very dangerous to use.
Thus, there are needs for improved methods of consolidating proppant particles in subterranean fractures whereby all of the proppant particles are consolidated into high strength permeable packs in the fractures which do not permit the flow-back of proppant, formation sand and the like. Further, there are needs for improved hardenable resin compositions and/or the components thereof that have long shelf lives and high flash points, i.e., flash points above 125° F.
SUMMARY OF THE INVENTION
The present invention provides improved methods of coating dry proppant particles with a resin composition and suspending the coated proppant particles in a fracturing fluid as well as improved hardenable resin compositions and components thereof 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 high strength permeable packs in fractures formed in subterranean zones which do not allow proppant flow-back. The methods 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 and optionally, a viscosifying agent for viscosifying the carrier fluid and dispersing the hardening agent when the hardening agent is a particulate solid. 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 one or more fractures therein and to place the hardenable resin composition coated proppant particles in the fractures. As the fractures are formed by the fracturing fluid, the liquid hardenable resin component is mixed with the liquid hardening agent component to form a liquid hardenable resin composition. The liquid hardenable resin composition is continuously coated on dry proppant particles conveyed from the source of the dry proppant particles. The resulting hardenable resin composition coated proppant particles are continuously mixed with the fracturing fluid whereby the hardenable resin composition coated proppant particles are suspended in the fracturing fluid and are deposited in the one or more fractures formed wherein they are caused to harden and consolidate into a high strength permeable pack which prevents proppant flow-back. 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, the coating of the dry proppant particles with the hardenable resin composition and the mixing with and suspending of the resin composition coated proppant particles with the fracturing fluid are terminated. The hardenable resin composition on the coated proppant particles is allowed to harden and to consolidate the proppant into one or more high strength permeable packs which prevent proppant flow-back.
Another improved method of the present invention for coating dry proppant particles with a resin composition and suspending the coated proppant particles in a fracturing fluid, the resin composition hardening and consolidating the resin coated proppant particles into a high strength permeable mass
Barton Johnny A.
Isenberg O. Marlene
McCabe Michael A.
Nguyen Philip D.
Weaver Jimmie D.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Neuder William
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