TECTONIC STRESS FIELD QUANTITATIVE MODEL AND PETROLEUM DISTRIBUTION IN LOW-ORDER COMPLEX FAULT BLOCKS

Quantitative models of three phases of tectonic stress fields,i.e.the phase of the First Member of the Shahejie Formation,Dongying Formation phase and the present phase,are constructed based on a study of the Xianhe low-order brush fault block system,and the characteristics of the tectonic stress fields and relation between the stress fields and hydrocarbon distribution are studied.Study indicates that the intensity,direction and magnitude of stress vary in different geologic periods.The stress values show a trend of increase from the old to young formations.The maximum horizontal principal stress in the tectonic stress fields becomes gradually low from the divergent side to convergent end of the brush structure in plan views and increases with depth in section.So the fault zone is a low-stress area and also an area for hydrocarbon accumulation.The authors propose that the stress transition zone is a low-stress area and a favorable area of low-amplitude faulted nose structure,as well as an area of residual oil in a complex fault block oil accumulation in the middle and late stages of petroleum exploitation.