New Results Improve Fracture-Cleanup Characterization and Damage Mitigation

Abstract

Summary It is well documented that hydraulic-fracture treatments, although successful, often underperform. Frac-and-pack completions exhibit positive skin values, and traditional hydraulic-fracture completions show discrepancies between the placed propped length and the effective production fracture length. Ineffective fracture cleanup is often cited as a likely cause. This paper presents some of the results of an investigation of fracture-cleanup mechanisms. This investigation was undertaken under a joint-industry project (JIP) active since the year 2002. The data discussed build on the initial results published in early 2006, which indicated that the polymer concentrates only in the filter cake, and that flow along the fracture encounters significant yield stress when the filter-cake cumulative thickness dominates the width of the fracture. The new results presented here demonstrate successful strategies that mitigate the effects of excessive filter-cake thickness. Experimental data demonstrate that flow along the fracture would encounter lower yield stress when the breaker is delivered directly to the filter cake as opposed to random distribution. The data also indicate that a smaller breaker amount delivered directly into the filter cake is more effective at reducing the yield-stress effects than a larger breaker amount delivered randomly in the slurry. Alternative breaker materials are explored, and additional data are also presented to estimate the yield-stress effect for fluid flow across the filter cake from the reservoir into the fracture.