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.
Read the paper synopses in the June 2012 issue of JPT.
Gerald R. Coulter, SPE, is a consulting petroleum engineer and president of Coulter Energy International. He is involved in consulting and technology transfer of well-completion, formation-damage, and well-stimulation technology. Coulter is currently an instructor with PetroSkills. His industry experience includes work with Sun Oil/Oryx Energy Company, Halliburton, and Conoco. Coulter has authored numerous technical papers and holds numerous patents, has been chairman of and has served on numerous SPE committees, and is currently serving on the JPT Editorial Committee. He holds a BS degree in geology and a BA degree in chemistry from Oklahoma State University and an MS degree in petroleum engineering from the University of Oklahoma.