Technology Focus: Well Stimulation (June 2012)

Abstract

Technology Focus Well stimulation continues to be a hot topic in our industry, particularly with hydraulic fracturing of shales. Having been in the industry since the Dark Ages, (at least, it seems like it at times), it is interesting to see the technology changes over time and what areas are currently in the spotlight. Certainly, hydraulic fracturing continues to lead the industry interest; however, we do pump a lot of acid, and we have not forgotten its importance. Our acid blends have not changed much since the very early days—the late 1800s—of acidizing. Hydrochloric acid has been the mainstay, with primarily hydrofluoric acid and formic and acetic acids being the complimenting acids. Specialty acids, such as phosphonic, sulfamic, and others, have also been playing a role. Major technology developments in nonproppant-fracturing well stimulation, as evidenced by the numerous publications over the last few years, have been primarily in carbonate acidizing. This is a continuing trend brought about by the significance of the carbonates to the world’s oil supply. However, our industry does use a lot of acid in the noncarbonates. One of those areas is in spearheading fracturing treatments to reduce near-wellbore tortuosity, most of these in sands and shales. My experience with this approach in horizontal shale wells has not always been successful; however, one of the papers selected for this month’s feature shows a unique acid blend that has shown some success in tight-gas-sand fracturing. Perhaps this and other unique acid blends could provide increased success in shales. Horizontal wells in all reservoir types are now quite common, allowing our industry to exploit lesser-quality reservoirs economically. Shales are excellent examples. Many reservoirs have a high water cut, and stimulating wells in these reservoirs can be a real challenge. Acid-placement techniques, as well as diagnostics while acidizing, are a significant challenge to our industry. Of course, in our industry, challenges beget solutions. A recent development helping with well stimulation and production diagnostics is distributed temperature sensing (DTS) and distributed acoustic sensing (DAS). From reviewing numerous technical papers from worldwide SPE meetings held in the last year or so, the development and application of DTS and DAS appear to be in the forefront. Two of the papers selected for this month’s feature reflect on these developments and applications. Readers are advised to review the following synopsized papers as well as the recommended additional reading to gain information on recent advancements in well stimulation. Recommended additional reading at OnePetro: www.onepetro.org. SPE 144803 Selective Stimulation and Water Control in High-Water-Cut Wells: Case Histories From Upper Magdalena Valley Basin in Colombia by E. Rodriguez, Ecopetrol, et al. SPE 154257 Acidizing Optimization: Monterey Shale, California by Rakesh Trehan, Halliburton, et al. SPE 143942 Sandstone Reservoir Stimulation Using High-Temperature Deep-Penetrating Acid by Puyong Feng, China Oilfield Services, et al. SPE 148835 Fracture-Stimulation Diagnostics in Horizontal Wells Using DTS by M. Tabatabaei, Texas A&M University, et al. SPE 152320 Stimulation in Wells With Electrical Submersible Pumps Increases Production and Saves Costs Without Damaging Pumps by M. Gallegos, Schlumberger, et al.