Modifying the Proppant Surface to Enhance Fracture Conductivity

Abstract

Abstract This paper describes laboratory studies and field testing that demonstrate how surface modification of proppant with polymeric "tackifiers" can improve the fluid conductivity of propped hydraulic fractures. It also identifies and describes several conductivity enhancement mechanisms that result from proppant-surface modification. Molecular simulations identified optimal intermolecular friction factors of the polymeric "tackifiers" that increases the proppant's intergranular friction. Once coated with a tacky surface-modification material, the proppant grain interacts instantaneously with the surrounding particulates resulting in a stabilized proppant bed. Experiments show that coating the proppant with these tacky polymeric materials hinders proppant settling in aqueous-based fracturing fluid; this characteristic results in better vertical distribution of proppant within the fracture and an increase in pack porosity. Conductivity measurements of proppant packs [in accordance with American Petroleum Institute (API) standards] support this observation and reveal the influence that closure stress plays in the final proppant-pack conductivity. Testing with a complete fracturing fluid system indicates that improved fluid removal is possible under certain conditions. Extensive field testing supports this conclusion by providing evidence of increased and sustained fracture productivity with faster and more effective well cleanup after water-based fracturing treatments. Because the proppant surface is modified on the fly and requires no additional time for curing, aggressive gel-break schedules and well flowback rates are used. The use of tacky, polymeric surface-modification materials stabilized proppant packs resulting in little or no backproduction of proppant or fines. This paper includes treatment results from formations that were hydraulically fractured with one of these surface-modification agents.