.-round Gusangnanxi Carbonate Reservoir Exploitation Mechanism

With increasing need for energy and further exploration and development of oil and gas, the development of fracture-cavern reservoir have been one of the focuses in China in recent years. Owing to the particular reservoir pore space of Sangnanxi fracture-cavern carbonate reservoir in Lungu, many problems need to be investigated, such as characterization of its geological features, research of flow characteristics, development scheme and relationship between recovery rate and productivity, study on the suitable production rate that can fully exert to its productivity, how to realize numerical simulation and the production mechanism of depletion development.On the basis of many people's research, the first step in this dissertation aims at the study on basic geological features, anisotropic properties and development characteristics of fracture-cavern carbonate reservoir. Then according to the flow equation of fracture-cavern media and compared it with ordinary dual-porosity media, the relationship of the interporosity form factor of these two kinds of dual-porosity media was established to realize numerical simulation of fracture-cavern carbonate reservoir. Based on its network-like feature, the reasonable development plan and well location were determined. Utilizing the numerical simulation software of Eclipse, depletion development mechanism was studied and a reasonable recovery rate model was established. In this way, a set of depletion development plan for Sangnanxi carbonate reservoir in Lungu was constructed.With the aid of multidisciplinary techniques, such as reservoir engineering, numerical simulation, applied statistics, Sangnanxi fracture-cavern carbonate reservoir in Lungu is studied and the acquired achievements are as follows:(1) Because the pore of matrix is not well developed in the fracture-cavern carbonate reservoir, it can not storage and flow fluids. In this type of reservoir, the fracture is the main room of flow channels, and the cavern is the main storage room.(2) According to its net-work characteristics, severe anisotropic properties and existing development technique, it is determined to develop it with natural depletion and progressive exploration and development.(3) For the existing conventional numerical simulators can not simulate this type of reservoir effectively, based on flow equations, the different flow characteristics between the fracture-cavern and fracture-matrix dual-porosity media are analyzed. According to mathematical expressions of flow coefficient in these two kinds of dual media, after amending the SIGMA of numerical simulation software, fracture-caverncarbonate reservoir can be simulated.(4) According to the intrinsical geological features of fracture-cavern carbonate reservoirs, the stepwise regression analysis method in multiple regression analysis is used to establish a reasonable recovery rate model at the early stage of depletion development in fracture-cavern carbonate reservoirs. In this way, oil recovery rates of different fracture-cavern carbonate reservoirs and production wells can be predicted.(5) The simulation software of ECLIPSE is used to investigate the depletion development mechanism of Sangnanxi carbonate reservoir in Lungu and make a performance prediction about depletion development. The research result shows that the depletion development has a preferable exploitation effect on Sangnanxi carbonate reservoir in Lungu.