浅谈水压致裂应力测量资料的解释与分析
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摘要
<正> 一、引言水压致裂原地应力测量,测量方法简便易行,事先无需知道岩石力学参数,可以重复、连续测量,结果比较可靠.同时还可提供其它测量方法不能得到的、工程上也很需要的一些岩石力学参数,如原地抗拉强度、完整岩石的破裂压力等.由于这一方法具有显著优点,近年来在国内外得以大力推广,现已被广泛应用于大型地下工程、抽水蓄能电站、
This paper deals with the analysis and interpretation of hydraulic fracturing measurement data. We first discuss the physical meaning of the instantaneous shut-in pressure (ISIP) and fracture pressure, the two key factors for determining principal stress magnitude and then demonstrated how to interprete them in the original pressure record. We suggest using the pressure parameters acquired from the third fracture reopening circle to determin principal stresses. The form of hydraulic fracturing record curve depends on the relative magnitudes of the breakdown pressure, P_b, the fracture reopen pressure, P_r, and the ISIP. It is quite possible that fracture reopen pressure, P_r, is larger than, less than or nearly equal to ISIP, It is one of the natural characteristics of the in-situ stress. Our measurement carried out at different places and liberatorial experiments have proved that the orientation of hydraulic fracturing plane can't stand for the direction of maximum horizontal principal stress unless the horizontal stress difference reached certain magnitude. The horizontal stress difference which will be necessary for the hydraulic fracture plane to indicate the reliable direction of maximum horizontal principal stress seems that the ratio of horizontal principal stress (S_H/ S_h) is about 1.4.
This paper deals with the analysis and interpretation of hydraulic fracturing measurement data. We first discuss the physical meaning of the instantaneous shut-in pressure (ISIP) and fracture pressure, the two key factors for determining principal stress magnitude and then demonstrated how to interprete them in the original pressure record. We suggest using the pressure parameters acquired from the third fracture reopening circle to determin principal stresses. The form of hydraulic fracturing record curve depends on the relative magnitudes of the breakdown pressure, P_b, the fracture reopen pressure, P_r, and the ISIP. It is quite possible that fracture reopen pressure, P_r, is larger than, less than or nearly equal to ISIP, It is one of the natural characteristics of the in-situ stress. Our measurement carried out at different places and liberatorial experiments have proved that the orientation of hydraulic fracturing plane can't stand for the direction of maximum horizontal principal stress unless the horizontal stress difference reached certain magnitude. The horizontal stress difference which will be necessary for the hydraulic fracture plane to indicate the reliable direction of maximum horizontal principal stress seems that the ratio of horizontal principal stress (S_H/ S_h) is about 1.4.
引文
① 郭启良译,水压致裂压力与时间函数关系的分析:关于识别关闭压力的五种方法的比较,地壳构造与地壳应力,4,1990．
① 高德禄译,T.W.Doe等著,静水压力和非静水压力条件下盐岩中水压致裂的定向,地壳构造与地壳应力,6,1991．
[1] Hubert, M.K., and D.G.Willis, Mechanics of hydraulic fracturing, Trans. AIME 210, 1957．
[2] Fairhust, C., Measurement of in-situ rock stresses, with particular reference to hydraulic fracturing, Rock Mech. and Engineering Geol., 2,1964．
[3] Haimson, B.C., and C.Fairhust, In-situ stress determination at great depth by means of hydraulic fracturing, in Rock Mechanics-Theory and practice, Proc. of 11th Symposium on Rock Mechanics, 1970．
[4] 李方全等,三峡坝区水库诱发地震研究--茅坪钻孔的现场测试与分析,地震出版社,1993．
[5] 郭启良等,松辽盆地油井水压致裂应力测量研究,地壳构造与地壳应力文集(7) ,地震出版社,1994．
[6] Stephen, H.et al., The interpretation of hydraulic fracturing pressure-time data for in-situ stress determination, Hydraulic fracturing stress measurements proceedings of a workshop, December 2～5, 1981．
① 高德禄译,T.W.Doe等著,静水压力和非静水压力条件下盐岩中水压致裂的定向,地壳构造与地壳应力,6,1991．
[1] Hubert, M.K., and D.G.Willis, Mechanics of hydraulic fracturing, Trans. AIME 210, 1957．
[2] Fairhust, C., Measurement of in-situ rock stresses, with particular reference to hydraulic fracturing, Rock Mech. and Engineering Geol., 2,1964．
[3] Haimson, B.C., and C.Fairhust, In-situ stress determination at great depth by means of hydraulic fracturing, in Rock Mechanics-Theory and practice, Proc. of 11th Symposium on Rock Mechanics, 1970．
[4] 李方全等,三峡坝区水库诱发地震研究--茅坪钻孔的现场测试与分析,地震出版社,1993．
[5] 郭启良等,松辽盆地油井水压致裂应力测量研究,地壳构造与地壳应力文集(7) ,地震出版社,1994．
[6] Stephen, H.et al., The interpretation of hydraulic fracturing pressure-time data for in-situ stress determination, Hydraulic fracturing stress measurements proceedings of a workshop, December 2～5, 1981．
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