Applicability of Tailored Pulse Loading for Gas Well Stimulation (1984)

Applicability of Tailored Pulse Loading for Gas Well Stimulation D.D. Keough; D.D. Keough SRI Intl. Search for other works by this author on: This Site Google Scholar D.R. Curran; D.R. Curran SRI Intl. Search for other works by this author on: This Site Google Scholar S.L. McHugh S.L. McHugh Lockheed Missile and Space Co. Inc. Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Unconventional Gas Recovery Symposium, Pittsburgh, Pennsylvania, May 1984. Paper Number: SPE-12837-MS https://doi.org/10.2118/12837-MS Published: May 13 1984 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Keough, D.D., Curran, D.R., and S.L. McHugh. "Applicability of Tailored Pulse Loading for Gas Well Stimulation." Paper presented at the SPE Unconventional Gas Recovery Symposium, Pittsburgh, Pennsylvania, May 1984. doi: https://doi.org/10.2118/12837-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Unconventional Resources Conference / Gas Technology Symposium Search Advanced Search AbstractTailored-pulse loading is a gas well stimulation technique that is promising for particular situations. The key factor in determining the probability of success is the interaction of the loading probability of success is the interaction of the loading history with the material properties and in situ stresses of the geologic formation. On the basis of theoretical and experimental studies, tailored-pulse loading is expected to be successful if (a) the rock is fairly competent, (b) the yield stress is greater than about 100 MPa, (c) the overburden pressure is less than about 100 MPa, (d) the natural fracture or joint spacing is less than several meters.BackgroundThe use of propellants or low-energy release rate explosives to stimulate oil or gas wells has been studied extensively during the past several years in programs funded by the Morgantown Energy Technology programs funded by the Morgantown Energy Technology Center (METC), other agencies of the Department of Energy, and the Gas Research Institute (GRI). The postulated advantages of the technique include the postulated advantages of the technique include the ability to create radial cracks at the borehole wall without causing rubblization and to drive the cracks by internal gas pressurization into the formation with their orientation unaffected by in situ stresses. During a recent GRI-funded program, Sandia National Laboratories Albuquerque (SNLA) demonstrated the practical feasibility of the tailored-pulse loading (TPL) technique in well is at Rowan County, Kentucky, and Meigs County, Ohio.The purpose of this paper is to discuss the expected limitations of the TPL technique and to describe the laboratory tests required to both properly assess the potential of a given formation for TPL stimulation and to roughly predict the extent of permeability enhancement that is expected. To accomplish permeability enhancement that is expected. To accomplish this objective, we use the results of a three-year METC-funded program at SRI. During that program, SRI worked with SNLA, Science Applications, Inc., the University of Maryland, and Los Alamos National Laboratories (LANL) to perform laboratory experiments, to develop computer models of the fracture process, and to use the models to predict the process, and to use the models to predict the results of field experiments performed at the Nevada Test Site.LIMITATIONS OF THE TPL TECHNIQUEThe scenario for a TPL stimulation is illustrated in Fig. 1. If the rise time of the pulse produced at the borehole wall is shorter than the time required for a sound wave to run around the borehole circumference, then multiple cracks can be produced by the circumferential tensions. However, several other requirements restrict the applicability of the technique. First, the circumferential tensions must be greater than the tensile strength of the rock. This requirement is easy to meet for moderate overburden pressures. However, two additional requirements are pressures. However, two additional requirements are that the peak radial compressive stress be lower than the compaction strength of the rock if it is porous and that the radial compressive stress also porous and that the radial compressive stress also be lower than that required to cause the rock to yield. If the above requirements are not met, the compaction and/or flow around the borehole will form a "stress cage" that tends to seal off the borehole from the fractured formation.Although it is relatively easy to produce TPLs that fulfill one or two of the above requirements, it may in some formations prove difficult to fulfill all of them simultaneously. Fortunately, in Devonian shale the porosity is low, the tensile strength is not excessive, the yield stress is relatively high, and SNLA was able to successfully create radial cracks in the formations in the Rowan and Meigs County stimulations where the overburden pressures were not excessive (less than 40 MPa).Another requirement for successful application of TPL is that the radial cracks be driven far enough by the gas pressurization to intersect the natural fractures in the formation. The importance of gas penetration into the cracks is illustrated in Figs. penetration into the cracks is illustrated in Figs. 2–4, which show the results of laboratory experiments in Plexiglass blocks containing scale model boreholes loaded by a low-power explosive. In one case the borehole was sheathed to prevent gas penetration, whereas in the other case the explosive penetration, whereas in the other case the explosive gases were allowed free access to the radial cracks. The gases drove the cracks 5 to 10 times farther than did the stress waves alone.P. 67 Keywords: overburden pressure, linear gas pressure gradient, fracture, history, coefficient, dyn cm2, upstream oil & gas, borehole, shale gas, loading Subjects: Hydraulic Fracturing, Unconventional and Complex Reservoirs, Shale gas This content is only available via PDF. 1984. Society of Petroleum Engineers You can access this article if you purchase or spend a download.