The Prediction Of Fractures In Carbonate Rocks In The Composite Fields

In recent years, the focus of petroleum exploration and development has turned to the complicated oil and gas reservoirs, especially the fractured oil and gas reservoirs. In this kind of reservoir, reservoir fractures are the storage space of oil and gas accumulation, as well as the channel of oil and gas transportation. It plays a very important role in the formation of this reservoir. Therefore the research of fracture development has become a hot research topic. The rocks are under the interaction of multiple physical fields, collectively referred to as the ‘composite fields’. The mechanism in the composite field is very complicated. This paper is based on the previous research, taking the north region of Renqiu buried hill Ordovician in Jizhong region as an example. The stress distribution in the reservoir in carbonate rocks in the composite field was simulated through finite element software, based on local geology and logging data. Then combined with the corresponding criterion of rock failure, the development of fracture in the region would be predicted.According to the research, the following results can be obtained:(1) The rock mechanics parameters were obtained by logging data, which is a more economical and convenient way to define mechanics parameters and the accuracy can be guaranteed.(2) The rocks in this region are mainly brittle carbonate rocks. Structural fracture is the major crack type with some corroded fissures, while other crack types are minor.(3) In this paper, the research of the mechanism of the composite field was conducted and the three-dimensional numerical simulation under composite field was employed, it can reflect the actual geological conditions better than other data models.(4) The principal stress in this region distributed generally in the-65 MPa ~-115 MPa, state of compressive stress. Besides, it is apparent that the stress value of fault internal is less than the continuous formation.(5) The development of fracture is obtained through the combination of the calculated stress values with the corresponding criterion of rock failure. It is found that the degree of fracture development around the fault is higher. Besides, the feature of crack distribution is area or block. Compared with the distribution figure of the wells, it is found that the areas that have intensive oil wells coincide with the areas where the indexs of fractures development are high. It is proved that the result is consistent with the actual situation.