Study On Productivity Decline Rule In The Process Of Relying On Natural Energy Development In Extra-low Permeability Reservoir

Recent years, the low permeability reservoir reserve is the main type of increasing reservoir and production in Chinese petroleum industry. Effective exploitation of low permeability resources has important political and economic significance, which can alleviate domestic oil demand and guarantee energy security. There are many researches on production law of low permeability reservoir at home and abroad, however, the analysis on influencing factors is still not perfect. Considering these influencing factors, the Steady-state replacement method and numerical simulation method are established, and the verification of the methods developed in this thesis is achieved by combining with the specific situation of the actual field.Flooding is difficult in abnormal high pressure and pressure sensitive low permeability oil reservoir, so, artificial fracturing is used based on natural depletion development. During the development, the production of producers is affected by many factors, such as the attenuation of formation energy, threshold pressure gradient and the attenuation of fracture flow capacity. Based on the factors mentioned, the fluid-solid coupling mathematical model is established with the consideration of pressure sensitive effect and the dynamic attenuation of fracture flow capacity. The research also establish another semi-analytic mathematical model, which consider the attenuation of formation energy, threshold pressure gradient, pressure sensitive effect and the attenuation of fracture flow capacity. Based on the mentioned, the Steady-state replacement mathematical model is established, and the software is developed. Both of the soft-wares are developed for the fast prediction of production decline laws. The concept model for abnormal high pressure and pressure sensitive low permeability oil reservoir is built, and its production decline law is studied. The results indicate: shorter well spacing means poorer bottom hole pressure maintenance and faster attenuation of fracture flow capacity, and lower threshold pressure gradient, and faster decline of formation pressure means faster production decline rate; when pressure sensitive effect is taken into account the production decline rate is obviously faster than that without the consideration of pressure sensitive effect. Both methods are applied to the adaptation and prediction of production decline laws in Block Liang112 in Boxing depression, and good results are achieved.