| The in-situ stress affects not only the artificial fracture in the form and spread, but also the dominant direction of oil and gas percolation, the well network deployment and development programmes formulated. In this paper, taken the theory and method of the petroleum geology, the structural geology, the rock mechanics, the geophysical well logging and the reservoir engineering for guidance, the in-situ stress characteristics of Niuquanhu oil field Santanghu basin and the influence on oil field development are systematic studied. The main results are as follows:(1) The structural feature affects the distribution of the in-situ stress of Xishanyao formation, three-dimensional stress become smaller from north to south and after first decrescent become bigger from west to east. The biggest principal stress is vertical stress, by the influence of tectonic stress, the horizontal maximum principal stress and the vertical stress are not quite differing, and the ratio is 1:1.(2) The in-situ stress type of Xishanyao formation areσz>σx>σy andσx>σz>σy, therefore the secondary cracks generated from hydraulic fracturing are basically NE-SW trending vertical joints. The fracture pressure is positively correlated with three-dimensional stress and most influenced by horizontal minimum principal stress.(3) The dominant direction of fluids percolation is NE-trending and is consistent with regional horizontal maximum principal stress direction. The same direction of injection-production wells and regional horizontal maximum principal stress is one of the major reasons for the problem of high water cut in oil wells, actions such as sup-breakdown pressure injection and hydrofracturing speed up the water cut in oil well increases.(4) The varying in-situ stress has more influence on reservoir stress field. As formation pressure increases, horizontal in-situ stress value also increases, and the corresponding reservoir rock fracture pressure increased.
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