Abstract

Upper-Shaximiao formation gas-bearing reservoir belongs to low-porous, low-permeable overpressured gas reservoir; and the stress field plays an important role in its exploration and development. By making full use of the structural configuration, the fracture distribution, the evolution history of structural configuration and core's traces acted by stress field, its characteristic can been obtained as follows: Xinchang gas field has been formed in an extrusion stress field of NNW-SSE direction for a long time, the direction of extrusion stress field had changed into west-east once in the later Himalaya period; the stress value is not big, the maximum principal horizontal stress is slightly bigger than the vertical stress and fracture pressure of rock layers, its main direction is about 150°. Based on the test parameters of rock mechanics and the deformation environment of regional structure, referring to the test results of hydraulic fracturing and the characteristics of the stress field, three-dimensional-ssoftware is utilized to simulate the stress field of objective formation numerically, and the relationship of the simulated stress field is: most maximum principal stress?vertical principal stress? minimum principal stress, maximum principal stress and minimum principal stress are on the horizontal plane; the maximum principal stress is –53?–68Mpa, only several Mpa greater than the fracture pressure of sandstone, and the minimum principal stress is – 45?–52Mpa; its value is low; showing that the structure deformation degree of objective formation is weak. Therefore, the coincidence degrees among simulated results?the characteristics of stress field and the stress measured data are high. 1. Based on making researches on a lot of low-porosity and low-permeability hydrocarbon reservoir, Introduction the effect of its exploration and development is determined by the development and distribution of fracture in the reservoir, not by the distribution and change of its permeability. The stress field of objective formation controls the form, extension and closure of fracture. Therefore, the research of the earth stress has very important significance in the exploration and development of low-porosity, low-permeability hydrocarbon reservoir.

Earth stress is a kind of internal stress existing in the earth crust, and is an applied force on unit area in medium, and the forces of vertical and horizontal movements, and the force of other factors cause the applied force. Although there are a lot of measuring techniques for the stress, each technique has its definite defect.

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CHARACTERISTICS AND MATHEMATICAL SIMULATION OF STRESS FIELD OF UPPER-SHA
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