New Technologies Enhance Efficiency of Horizontal, Multistage Fracturing

Abstract

Technology Update Significant differences in completion philosophy are emerging within our industry. Even companies that practice a factory mentality (one size/method fits all) are beginning to see that the “sledgehammer approach” to hydraulic fracturing may not be the most effective in draining horizontal wells in resource plays. For several years, we have seen massive increases in fluid volume, pumping rate, total proppant volume, and pumping time to increase recovery. We have seen through microseismic as well as fracturing into offset wells, that we are able to create massive and extremely long hydraulic fractures. Yet, when effective fracture length is calculated, the results are extremely disappointing. It only makes sense that “more is better.” However, after years of steadily increasing job size, stage number, perforating strategy, proppant volume, and lateral length, the only one that stands out as consistently improving recoveries is that more stages are required to effectively drain microdarcy permeability rock (Rankin et al., 2010). What We Have Learned Building an understanding of shale gas, unconventional gas, tight carbonate reservoirs, and more recently the renewed emphasis on oil and high-liquid gas formations has not been easy. Perhaps this is because of the extremely rapid pace of development and the acceptable economics of many projects in North America and throughout the world. Also, the diversity of applications for horizontal, multistage fracturing has made it more difficult to pin down best practices. As a massive body of data develops, a number of things have become clear. First, when equivalent stage numbers and proppant volumes are considered, open hole generally seems to outperform cased hole by 25% to 70% in production (Fig. 1, Edwards et al., 2010; Snyder and Seale, 2010). Second, the number of stages required to effectively drain microdarcy permeability rock is extremely high. Just a few years ago, performing 20 stages seemed too high to consider. Current stage numbers are often double that. Third, today’s common plug and perf practices—even at high densities—may not be sufficient to drain shale gas or tight oil, even after 15 years of depletion time (Quirk, 2010). Reservoir modeling indicates that evenly spaced fractures would effectively drain today’s reservoirs in North America. The actual production data, however, indicates otherwise.