A New Technique for Rapid Estimation of Fracture Closure Stress When Using Propellants (2002)

A New Technique for Rapid Estimation of Fracture Closure Stress When Using Propellants D.A. Cuthill; D.A. Cuthill Computalog Wireline Services Search for other works by this author on: This Site Google Scholar J.F. Schatz; J.F. Schatz John F. Schatz Research & Consulting, Inc. Search for other works by this author on: This Site Google Scholar J.V. Gilbert J.V. Gilbert Marathon Oil Company Search for other works by this author on: This Site Google Scholar Paper presented at the SPE/ISRM Rock Mechanics Conference, Irving, Texas, October 2002. Paper Number: SPE-78171-MS https://doi.org/10.2118/78171-MS Published: October 20 2002 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Cuthill, D.A., Schatz, J.F., and J.V. Gilbert. "A New Technique for Rapid Estimation of Fracture Closure Stress When Using Propellants." Paper presented at the SPE/ISRM Rock Mechanics Conference, Irving, Texas, October 2002. doi: https://doi.org/10.2118/78171-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/ISRM Rock Mechanics Conference Search Advanced Search AbstractMinifracs are used to assist with main hydraulic fracture design by generating estimates of the fluid efficiency, closure stress, fracture geometry, and leakoff coefficient prior to the main treatment. Closure stress is frequently determined by analyzing the pressure falloff response after pump shut-down using a Nolte G-Function analysis plot. Comparison of the measured data with the dimensionless Nolte G time indicates closure when used in combination with the derivative and pressure superposition derivative.During perforating/propellant treatments of wells, the use of a high-speed downhole digital pressure data recorder enables a new rapid technique for determining closure stress using the G-Function and associated methods. The propellant event breaks down the perforations and extends fractures into the formation in the time span of tens of milliseconds, and can thus be treated as a high-speed minifrac. The analysis method and feasibility of this new technique are demonstrated.The falloff pressure curve after a propellant event, typically lasting no more than a few hundred milliseconds, is shown in several case histories to provide sufficient closure information. Where these data are available, results are consistent with other methods. Although certain favorable conditions must exist for the method to be applicable, this new technique can be used where a quick estimate of closure stress is needed prior to hydraulic fracturing and while equipment is in place in the field. Work continues to fully define the range of applicability and accuracy of the new technique.IntroductionOriginally high-speed downhole pressure recorders were used with propellant stimulation applications to assist propellant tool design; enhance development and validation of the pre-job design model; and to ensure that the stimulation system did not adversely impact the mechnical wellbore components. The most important use of the recorder was in model confirmation as the data can substantiate that the propellant did in fact initiate and extend fractures into the formation.As numerous pressure records were gathered, qualitative analysis began to identify certain charactistics in the data that appeared to be formation/area specific, leading to the view that there may be additional information captured during the propellant stimulation event. If the formation was fractured then it was reasonable that fracture closure might be observable in the pressure falloff data.A number of techniques are currently in use to analyze well fracturing pressure falloff data. The G-Function analysis was one such technique identified that could be easily applied to the propellant pressure data. Case studies are presented which demonstrate the applicability of the technique using data gathered over milliseconds rather than minutes. One of the case studies is supported by minifrac data gathered after the propellant stimulation event was completed.The Propellant Fracturing ProcessIt has been known for some time that propellants can break down perforations and extend fractures into the formation. Propellants can now be combined with perforating guns to perform the perforation, breakdown, and fracture extension process in a single step6. Propellant-driven fractures are not as long as most hydraulically driven fractures, but can be used to enhance subsequent hydraulic fracturing jobs or perform mild stimulation or remediation of damaged wells in otherwise good reservoir. Recent work has shown that the process can be modeled on a computer for design and analysis purposes1. The computer model, PulsFrac, has been validated by comparison with laboratory observations and downhole field measurements of high-speed pressure data. This work has led to the following conceptual understanding of how propellants fracture the formation through casing in combination with a perforating gun. Keywords: plug back, propellant, new technique, perforation, closure analysis, fracture closure stress, closure pressure, upstream oil & gas, leakoff, rapid estimation Subjects: Hydraulic Fracturing, Perforating, Completion Installation and Operations, Completion Operations This content is only available via PDF. 2002. Society of Petroleum Engineers You can access this article if you purchase or spend a download.