Green Oilfield Fracture Characteristics And The Impact Of The Development Process

Fracture in the reservoir of QingXi oil field grows widely. It is not only the important storage space, but also the main flow passage for the oil and gas. For this reason, the research on fractures is of significance for the reserve estimation, the productivity to achieve and recovery in QingXi oil field.A method which is based on the technology of fractal and fractal dimension and well logging data has been developed and been used to calculate pore structure index and the fracture porosity in the fractured reservoir quantitatively in this paper. The method has provided another way for obtaining formation pore structure index. So the pore structure index is no longer only relied on core test in lab. The method above can also be used to calculate the pore structure index of non-fractured reservoir.Based on the achievements of the modern rock mechanics, by using of image logs dual caliper logs and so on comprehensively, the fracture extended direction and fracture area around borehole and in-situ horizontal stress direction have been obtained in the Qingxi .On the basis of the prediction of in-situ horizontal stress direction, the fracture areas of inter-well could be obtained. The results also show that In the reservoir of Qingxi oil field, both the fracture and the vug have grown; especial the interlayer fracture is in well growth. In Kulong mountain area in Qingxi oil field, the main direction of fracture distribution tends to the same as the direction of the in-situ maximum horizontal stress. The primary earth stress controls the growth of the fracture.The results of stress sensitivity experiment show that matrix rock of Qingxi oil field is weak stress sensitivity, but for the fracture, it's very strong. So, at the beginning of production in this field, Keeping reservoir pressure and limiting production are important and essential.The closure rules of fracture in different occurrence are also calculated and analyzed during production by using elastic-plastic finite element method of contact theory. The results show that fractures with low dip angle in Qingxi, especial horizontal interlayer fractures, tend to close easily due to inside fracture pressure dropping down. The closure pressure of fractures with low dip angle is relative high. By using of finite element method can achieved the critical closure pressure step by step, but the work is very complex and it is not convenient for the well-site operation. It is possible that the critical closure pressure couldn't be obtained because of rock sample failure during lab test and no rock sample with natural fracture for test. So At the end of this paper, base on simplified elastic-plastic constitutive model ,a elastic-plastic contact analytic model to calculate the critical fracture closure pressure has been established and discussed.