A Novel Hydraulic Fracture Evaluation Method Using Downhole Video Images to Analyse Perforation Erosion

Abstract

Abstract Perforation erosion and consequential changes to perforation friction pressure have a significant practical influence on limited entry hydraulic fracturing treatments and have been comprehensively documented (Cramer 1987), (Crump, Conway 1988), Long (2015) and others. Both effects are widely acknowledged but undesirable phenomena that stimulation specialists encounter and must mitigate during every treatment. The emergence of the alternative fracture diagnostic method described in this paper means however that perforation erosion can also have beneficial consequences for those trying to diagnose and optimize fracturing performance. The latest generation of borehole video cameras efficiently capture high definition images of erosion to individual perforations after hydraulic fracture treatment. Qualitative and quantitative evaluation of these images allow confirmation of proppant placement and fracture initiation depths that are resolved to the location of individual perforations. The methods described updates the previous work of Roberts, Lilly and Tymons (2018) to now directly quantify perforation erosion. This improves the identification of clusters that have been successfully stimulated against those that are under or over-stimulated. Measurement and comparison of perforation erosion, area, diameter and azimuth permit a statistical evaluation of the consistency of fracture distribution across clusters and stages. In their goal for optimal recovery Stimulation Engineers, Geoscientists and Reservoir Engineers evaluating treatment success have a fundamental question to answer - where exactly did the frac go? This apparently simple question has hitherto proven difficult, and costly, to answer. We demonstrate that evaluating perforation erosion provides straightforward and intuitive data to precisely confirm proppant placement, define the origin of individual fractures and help quantify treatment distribution. We present results illustrating the effectiveness of the method including examples of acquired perforation images. New methods are introduced demonstrating evaluation techniques used to confirm proppant transport through specific perforations, fracture initiation and treatment consistency. Initial work to demonstrate in-situ correlation between erosion and pumped proppant volume / weight is presented. We conclude that the method can be successfully applied to evaluate changes to stimulation treatment design parameters such as stage length, cluster number and spacing, proppant and fluid properties, pumping criteria and many aspects of perforation design including perforation charge type, count per stage and cluster and shot orientation. Existing hydraulic fracture diagnostic methods are limited in number, scope and sometimes accuracy. Analysis of in-situ perforation erosion using visual analytics provides an additional and complementary data source to evaluate the success of engineered treatment programs. The method provides measurements at a depth resolution that is not otherwise possible, allowing specific entry holes and fracture initiation points to now be evaluated.