Research Of Reservoir Characteristics And Flow Mechanism Of Fracture-cavern Carbonate Reservoirs In Lungu Oil Field Directed By Xiong Wei

Lungu oil field is the biggest marine carbonatite oil field; the main oil layer of Ordovician is cavity-fractured carbonatite in Yijianfang Formation and Yingshan Formation of middle and lower Ordovician. The main oil layer is characterized by deep burial, discrete spatial distribution, heterogeneity, complex relationship between oil and water. Currently, at home and abroad, the law of fluid flow in the cavity-fractured carbonate reservoir is not enough understanding, the development theory aimed this type of oil field has not form, the technology targeted poor, resulting in a lower level of overall development of these reservoirs.Firstly,the study on the reservoir characteristic though field data showed that the porosity and permeability in the bed rock is too low to be the effective reservoir, the fracture and cavity developed well, the main flow channel was fracture and the main storage space was cavity.Secondly, based on the characteristic of reservoir and the situation of the well drilled, the study and dipartition of unit of storage and seepage of single-well in Lungu cavity-fractured carbonatite reservoirs is carried.Thirdly, the law of flow was studyed though the physical modeling and mathmetics modeling based on the divided model of unit of storage and seepage of single-well. The study showed that the pressure and the production decrease exponentially with time in single cavity unit when bottomhole pressure is constant; the pressure and the production decrease multi-exponentially with time in multi cavity-fracture unit when bottomhole pressure is constant; the water content stepped changes with fractures in fracture aside cavity unit and the number of steps equal to that of the fractures. And formed a calculation method of the volume of water and oil in caves by production data and water-oil PVT calculationFinally, the analysis of developed wells in carbonatite reservoirs based on the theory of flow in cavity-fractured oil field showed that the theory is in good agreement with practice.The theory of flow in cavity-fractured reservoirs is the theoretical basis of identification and calculation of development indicator in unit of storage and seepage of single-well and direct the development of the cavity-fractured reservoirs.