Recording curves of four-arm caliper logs obtained from 36 wellbores in Zhongyuan oil field have been processed and analysed with computer programs. Orientations of principal stress axes in Dongpu seg,where theZhongyu...Recording curves of four-arm caliper logs obtained from 36 wellbores in Zhongyuan oil field have been processed and analysed with computer programs. Orientations of principal stress axes in Dongpu seg,where theZhongyuan oil field is located, are inferred from dominant azimuths in which severe bore wall breakouts tookplace. The result shows that the maximum horizontal principal compressive stress axis in the northern part ofthe seg lies in the direction of N(79±6°)W, while in the southern part it is in N (79°±18°)E, retaining a didference of about 22°between the former and the later. A two dimensional finite element simulation using alinear elastic plane stress model indicates that the clock-wise rotation of the principal stress direction in thenorthern Dongpu seg relative to that in its surroundings may be attributed to the softness of the seg rocks andits geometry of narrow northern and wide southern part. The magnitude range of the maximum and minimumhorizontal principal stresses is estimated from the most shallow depth at which the radially unsymmetric elongation of a wellbore initiates. Finally, evidences showing local variation of stress state with sites and depths are presented.展开更多
文摘Recording curves of four-arm caliper logs obtained from 36 wellbores in Zhongyuan oil field have been processed and analysed with computer programs. Orientations of principal stress axes in Dongpu seg,where theZhongyuan oil field is located, are inferred from dominant azimuths in which severe bore wall breakouts tookplace. The result shows that the maximum horizontal principal compressive stress axis in the northern part ofthe seg lies in the direction of N(79±6°)W, while in the southern part it is in N (79°±18°)E, retaining a didference of about 22°between the former and the later. A two dimensional finite element simulation using alinear elastic plane stress model indicates that the clock-wise rotation of the principal stress direction in thenorthern Dongpu seg relative to that in its surroundings may be attributed to the softness of the seg rocks andits geometry of narrow northern and wide southern part. The magnitude range of the maximum and minimumhorizontal principal stresses is estimated from the most shallow depth at which the radially unsymmetric elongation of a wellbore initiates. Finally, evidences showing local variation of stress state with sites and depths are presented.
