Compliance of Drillingrod System for Hydrofracturing in Situ Stress Measurement and Its Effect on Measurements at Great Depth

Abstract

Abstract:

The widelyaccepted hydrofracturing system in China mainland consists of six parts, iecontrol system for hydraulic fluid, highpressure pump, power supply system, data recording system, straddle packers, and watertight drilling rods. This whole testing system can be divided into two kinds: one is the shallow testing system for boreholes with depth less than 100 m, the other is the deep testing system for boreholes with depth more than 100 m.As for the drillingrod hydrofracturing measurement system, the elastic deformations of drilling rods, connection highpressure hoses and rock mass around testing interval have little effects on the compliance of testing system, and the elastic deformation of packers and the compressibility of fracturing fluids are two major factors. When testing interval is less than 100 m in depth, the compliance of testing system is controlled by the elastic deformation of packers and the compressibility of fracturing fluid, and when testing interval is greater than 100 m in depth, the compliance of testing system is controlled by the compressibility of fracturing fluids. For the testing at great depth, due to the large compliance of testing system, it is very difficult to determine the reopening pressure Pr0 In order to eliminate the negative effects from the compliance of testing system during the measurement campaign in deep boreholes, it is recommended to adopt other methods to determine Tfh, the tensile strength of rock mass around the testing interval so as to determine the maximum horizontal principal stress SH, or utilize other techniques to estimate SH. In the future research, the potential feasible way is to develop new downwell pressure gauges and flow meters in order to completely eliminate the negative effects from the compliance of testing system.

Key words: hydrofracturing, compliance of testing system, reopening pressure, drilling pipe type, flow rate

WANG Cheng-Hu, SONG Cheng-Ke, GENG Bo-Rui. Compliance of Drillingrod System for Hydrofracturing in Situ Stress Measurement and Its Effect on Measurements at Great Depth[J]. Geoscience, 2012, 26(4): 808-816.

References

［1］Hubbert K M,Willis D G. Mechanics of hydraulic fracturing
[J]. Petroleum Science and Technology，1957, 210:153-166.
［2］Scheidegger A E. Stresses in the Earths crust as determined from hydraulic fracturing data
[J]. Geologie und Bauwesen, 1962, 27：45-53.
［3］Kehle R O. Determination of tectonic stresses through analysis of hydraulic well fracturing
[J]. Journal of Geophysical Research, 1964, 69：252-273.
［4］Fairhurst C. Measurement of in situ rock stresses with particular references to hydraulic fracturing
[J]. Rock Mechanics and Engineering Geology, 1964, 2：129-147.
［5］Haimson B C, Fairhurst C. Initiation and extension of hydraulic fractures in rocks
[J]. Society of Petroleum Engineers Journal, 1967, 9:310-318.
［6］Haimson B C. Hydraulic fracturing in porous and nonporous rock and its potential for determining in situ stresses at great depth
[D]. Twin Cities：University of Minnesota, 1968：1-50.
［7］Von Schonfeldt H, Fairhurst C. Field experiments on hydraulic fracturing
[J]. Society of Petroleum Engineers, American Institute of Mining Engineers Journal,1972,12：1234-1232.
［8］Haimson B C. Earthquake related stresses at Rangely, Colorado
[M]// The American Society of Civil Engineers. The 14th U.S. Symposium on Rock Mechanics.University Park: The American Society of Civil Engineers,1972:689-708.
［9］Raleigh C B, Healy J H, Bredehoeft J D. An experiment in earthquake control at Rangely, Colorado
[J]. Science, 1976, 191:1230-1237.
［10］Amadei B, Stephansson O. Rock stress and its measurement
[M]. London：Chapman & Hall, 1997：1-50.
［11］Haimson B C, Cornet F H. ISRM suggested methods for rock stress estimation—Part 3: hydraulic fracturing (HF) and/or hydraulic testing of preexisting fractures (HTPF)
[J]. International Journal of Rock Mechanics & Mining Sciences, 2003, 40(7/8): 1011-1020.
［12］刘允芳. 岩体地应力与工程建设
[M]. 武汉：湖北科学技术出版社，2000:1-100.
［13］谢富仁，陈群策，崔效锋,等.中国大陆地壳应力环境研究
[M]. 北京: 地质出版社, 2003:1-100.
［14］安其美，赵仕广，丁立丰,等. 单回路双栓塞止水压水技术及其应用
[J]. 水力发电学报，2004,23(5)：50-57.
［15］Kuriyagawa M, Kobayashi H, Matsunaga I, et al. Application of hydraulic fracturing to threedimensional insitu stress measurement
[J]. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts,1989, 26:587-593.
［16］刘允芳. 水压致裂法三维地应力测量若干问题的探讨
[J].地震研究, 1999, 22 (3): 266-271.
［17］Cornet F H, Valette B. Insitu stress determination from hydraulic injection test data
[J]. Journal of Geophysical Research, 1989, 13：11527-11537.
［18］Cornet F H. Stress determination from Hydraulic Test on Preexisting Fracturesthe HTPF method
[M] //Proceedings of the International Symposium on Rock Stress and Rock Measurements. Lule: Centek Publication,1986:301-312.
［19］刘允芳. 在单孔中水压致裂法的三维地应力测量
[J].岩石力学与工程学报, 1999, 18 (3): 192-196.
［20］Ito T, Evansb K, Kawaia K, et al. Hydraulic fracture reopening pressure and the estimation of maximum horizontal stress
[J].International Journal of Rock Mechanics and Mining Sciences, 1999, 36 (5/6):811-826.
［21］Ito T, Igarashi A, Kato H, et al. Crucial effect of system compliance on the maximum stress estimation in the hydrofracturing method: Theoretical considerations and fieldtest verification
[J].Earth Planets Space, 2006, 58: 963-971.
［22］Jaeger J C, Cook N G W, Zimmerman R W. Fundamentals of Rock Mechanics
[M]. London: Blackwell Publishing, 2007：1-100.
［23］冀宏. 液压气压传动与控制
[M]. 武汉：华中科技大学出版社，2009:1-50.
［24］Ito T, Satoh T, Kato H. Deep rock stress measurement by hydraulic fracturing method taking account of system compliance effect
[M]//Xie Furen. Proceedings of the 5th International Symposium on Insitu Rock Stress. Boca Raton: CRC Press, 2010:43-49.
［25］Zoback Mark D. Reservoir Geomechanics
[M]. New York: Cambridge University Press, 2007:1-50.