Through the analysis of casting thin sections, 3D geological modeling, special logging series and micro seismic monitoring, reservoir stress characteristics of Jing’an area were studied. The results show that: 1) the distribution of the direction of micro pore and throat would cause the stress anisotropy; 2) differences in each layer of Chang 4+5₂ sandstone are big, the lateral superposition characteristics of multi-periods channels have the major influence on stress distribution; 3) the stress difference in the study area is generally not large with the value of 3?6 MPa, with the development of water flooding development, the variation of the two main stress varies in the reservoir, resulting in the multi-directional development of fractures in the process of repeated fracturing. The results can provide a scientific basis for improving oil recovery in the middle and late development of low permeability reservoirs.

Through the core observation, inter-well tracer test and water flooding front test, the fracture development characteristics of Chang-7 tight sandstone reservoir in Xin’anbian area of Ordos Basin are studied. The results show that maximum horizontal principal stress direction of Chang-7 tight sandstone oil reservoir in Xin’anbian area is NE60°?80°. The fracture type is mainly high angle fractures or vertical fracture, and fracture direction is NE75°?85°, the dip angle is 70°?85°. Dynamic monitoring data analysis shows that the micro fracture research area of tight sandstone oil reservoir developed widely and plays an important role in increasing the seepage channel and improving the permeability of matrix, water channeling easily along the fracture formation, resulting in the production of well water is fast. 3D geological modeling results show a high degree between oil saturation of tight sandstone oil reservoir in the study area and the degree of fracture development, which can effectively support the fracture of oil and gas reservoir and accumulation.

As to Chang 4+5 formation of special low-permeability Baiyushan reservoir in Ordos Basin reservoir, the hydraulic fracture distribution is not regular and difficult to predict. The method of traditional engineering geology and special logging, conventional well logging, micro facies research were combined. Through the stablishment of three-dimensional rock mass mechanics model of reservoir, the full length fracturing numerical simulation was carried out with the change of stress field. More accurate geometry parameters of fractures were got, stress interlayer insulation could be regarded as a kind of new development of geological property which would play an important role in fracture extension, then the development adjustment measures are put forward. The conclusion would provide an important scientific basis on decision-making efficiency in low permeability reservoir development and improve the residual oil recovery degree.