Study On 3-D Stress Field For Economical Effective Development Low Permeability Oil And Gas Resources In Daqing Oil Field

There are 30700×104 t low permeability oil resources in Daqing Oil Field. Economical effective development low permeability oil and gas resources need to use 3-D in-situ stress field.The state of in-situ stress field is one of the important and basic data for oil and gas exploration and development and for design of well drilling engineering. Although the in-situ stress measurement is still the most directly method for in-situ stress determination to this day, but in fact, the actual measurements for in-situ stress are very limited because of the costly expense and other conditionality. It is a fact that the distribution of in-situ stress field can not be generated by some discrete measuring points. Three-dimensional numerical simulation is an effective tool for research on regional in-situ stress field and it greatly attracts the attention of the scientists all over the world.Taking the petroleum geology, the geophysical well logging, rock mechanics, the well drilling project, the oil gas reservoir transformation, the oil gas pool engineering and the mufti-disciplinary theory and the method as the instruction, according to the research approach and procedure which include in-situ stress measurement, geological structure, inversion of in-situ stress field by finite element method and application of in-situ stress, 3-D numerical simulation of the in-situ stress field and its application in oilfield development has been systematic studied in this thesis. Some new outcomes and cognition have been acquired during the research on basic theory, technology, software development and application.Firstly, In view of the low degree of automation and accuracy of the in-situ stress numerical simulation, the optimization theory has been introduced to the inversion of 3-D in-situ stress field. And a method called constrained optimization inversion of 3-D in-situ stress field has been established with the finite element method (COFEMI), which has been developed based on the second development technique of ANSYS. Much research on improving post-treatment of 3-D in-situ stress field numerical simulation has been done. And a software package has been compiled which can give vector of in-situ stress in the form of contour diagrams in any special observation planes .And the software can also point out the area where the in-situ stress has been effected by faults and the influential level for different locations. The software has greatly increased the automation for 3-D in-situ stress field analysis, and it can also realize visualization of the results. Secondly, aiming at overcoming the deficiency of the in-situ stress numerical simulation, two mechanical models of fault have been studied in the thesis, including the model of heterogeneous continuous medium and the model of the discontinuous medium. The thesis has proposed some principles, summarized as feasibility and simplification, which should be followed when selecting the mechanical model of faultThirdly, based on rock mechanical tests and in-situ stress core tests, the thesis has systematically studied the in-situ stress of block SHU-25 in Sanzhao depression, Songliao basin. The 3-D in-situ stress field under the effect of faults has been established, and the thesis has put its emphasis on the area where the in-situ stress has been affected by faults and the influential level analysis for different locations. The effect regularity of faults on in-situ stress has been summarized. Also, the longitudinal distribution of the mechanical properties and in-situ stress, which include dynamic and static elastic parameters, fracture pressure, sand production index et al, has been generated using the well logging data.In the end,based on the 3-D in-situ stress field by the COFEMI method and the longitudinal distribution calculated using Logging Data. The application of in-situ stress in oil and gas development has been discussed, including fracture prediction, optimization procedure for hydraulic fracturing, sanding prediction, flooding well network optimization et al. The thesis has proposed some innovative approaches for improving oil and gas development in this block.