Methods and compositons for forming subterranean fractures containing resilient proppant packs

Abstract

Improved methods of forming fractures containing resilient proppant particle packs which prevent the production of sand and fines with produced fluids and prevent proppant flow-back in a subterranean zone penetrated by a well bore are provided. As the fractures are formed, a liquid hardenable resin component is mixed with a liquid hardening agent component and a liquid rubber component to form a hardenable resin composition. The hardenable resin composition is coated onto dry proppant particles which are suspended in the fracturing fluid and placed in the fractures. The hardenable resin composition on the resin composition coated proppant particles is allowed to harden and consolidate the proppant particles into high strength resilient permeable packs.

Description

[0001] 1. Field of the Invention[0002] 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.[0003] 2. Description of the Prior Art[0004] 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 forme...

AI Technical Summary

Benefits of technology

[0008] 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.

[0009] 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.

[0012] 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.

[0015] As is also well understood, when the fracturing fluid is broken and the hardenable resin composition coated proppant particles are deposited in the fractures formed, the fractures close on the proppant particles. The partially closed fractures apply pressure on the hardenable resin composition coated proppant whereby the proppant particles are forced into contact with each other while the resin composition hardens. The hardening of the resin composition under pressure helps bring about the consolidation of the resin coated particles into a hard permeable pack having sufficient compressive strength to prevent unconsolidated proppant and formation sand from flowing out of the fractures with produced fluids. In fracture treatments carried out in unconsolidated formations, good consolidation of proppant is required in the perforations which extend from the inside of the well bore through casing and cement into the unconsolidated formation as well as in the fractured portions of the unconsolidated formation surrounding the well bore. The last portion of the proppant which is deposited in the perforations and in the fractures is coated with the hardenable resin composition and is caused to harden. The resulting consolidated proppant in the perforations and fractures contributes to the prevention of proppant flow-back. However, there is often little closure pressure applied to the hardenable resin coated proppant in the fractures close to the well bore and there is no closure pressure applied to the hardenable resin coated proppant particles in the perforations. In addition, the hardenable resin coated proppant particles can be separated from each other by films of the gelled fracturing fluid and because of the presence of the fracturing fluid films, the proppant particles do not sufficiently consolidate. As a result, the consolidated permeable packs formed in the perforations and fractures often have less than sufficient compressive strength to prevent unconsolidated proppant and formation sand from flowing out of the perforations and fractures. These problems are solved by including in the hardenable resin composition one or more hydrolyzable esters which function to break gelled fracturing fluid films on the particles, and a surfactant for facilitating the coating of the resin composition on the proppant particles and for causing the hardenable resin composition to flow to the contact points between adjacent resin coated proppant particles so that the particles are consolidated into a high strength permeable mass.

Problems solved by technology

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.