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U.S. Department of Energy
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Theoretical and experimental analyses of hydraulic fracturing and some reservoir response to the stimulation

Conference ·
OSTI ID:6215416
Newly developed numerical models have been applied to analyze some aspects of fracture propagation near well bonded material interfaces to determine if these interfaces can inhibit propagation. Results from these calculations indicate that, for fractures propagating from a lower modulus material toward an interface with a higher modulus material, the stress intensity factor at the tip near the interface decreases significantly as the tip approaches the interface. However, upon penetration of the interfaces into the higher modulus material, the stress intensity factor is seen to increase abruptly and arrive at a higher value than in the lower modulus material. Small scale laboratory experiments are being performed to study the growth of hydraulically driven cracks in the vicinity of unbonded interfaces in rocks. Blocks of the materials being studied are held adjacent to one another under a static load. A hydraulically driven crack is initiated in one of the blocks. It is found that for blocks of the same material that penetration of the crack into the adjacent block is controlled by the normal stress across the interface and the finish of the interface surfaces. Experiments are performed to measure the frictional properties of the interfaces to better understand the mechanism of crack growth across the interface. Well pressure test data from a MHF stimulated well in the Piceance Basin was analyzed. Analysis of that data indicated that the length of the fracture in the productive rock was of the order of the lens size. Additionally, the analysis showed that the fracture had a finite conductivity or there was fluid damage to the fracture faces, but it was impossible to uniquely determine if either mechanism was dominant.
Research Organization:
California Univ., Livermore (USA). Lawrence Livermore Lab.
DOE Contract Number:
W-7405-ENG-48
OSTI ID:
6215416
Report Number(s):
UCRL-82578; CONF-790805-4
Country of Publication:
United States
Language:
English