Enhancing Well Performance by In-Stage Diversion in Unconventional Wells

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 180985, “Enhancing Well Performance by In-Stage Diversion in Unconventional Wells: Physics and Case Studies,” by F.E. FragachÁn, M. Pordel Shahri, D.M. Arnold, A.G. Babey, and C.S. Smith, Weatherford, prepared for the 2016 SPE Argentina Exploration and Production of Unconventional Resources Symposium, Buenos Aires, 1–3 June. The paper has not been peer reviewed. Developments in nondamaging, degradable diverters with outstanding plugging efficiency have opened new opportunities for protecting existing fractures by plugging them and then fracturing zones that were previously bypassed because of inefficient zone coverage or refracturing zones that were inefficiently fractured initially. With multistage operations becoming the industry norm, operators need easily deployable diversion technologies that will protect previously stimulated perforations and enable addition of new ones. This paper reviews several aspects of the use of in-stage diversion. Introduction to Degradable Diverters Polymer-based degradable diverters are temporary materials that are useful in some oil and gas operations, primarily to enable fluids to flow into areas of the reservoir where fluid dynamics would normally exclude them. While standard mechanical diverters work well for zonal isolation, they must be physically removed from the well after the workover job has been completed. Degradable diverters have performed an important role for many decades, but they cannot meet operational requirements to stay intact for weeks or even hours. Perforation balls or degradable ball sealers will fall away from perforations without continuous application of pressure. Rock salt and flakes will dis-solve after a few hours. High temperatures degrade the material faster. The suite of degradable diverter products consists of polymers of varying chemistries that provide good blocking and sealing when applied to the well but that can also degrade across a wide temperature range to monomer species that will be nondamaging to hydrocarbon-bearing formations. Diversion applications with degradation times between a few hours and a few days in temperatures from 80 to 325°F can be achieved by the selection of appropriate polymer chemistry. Despite the unique design of these various polymers, the success of applying this technology in the field for use as a temporary diverter is heavily dependent on sound engineering and geomechanical design that enables the creation of a seal over existing flow pathways that can withstand differential pressures up to and exceeding 8,000 psi and yet can completely degrade in a controlled amount of time after the completion of the intervention.