Research On Analysis Method And Prediction Of Production Decline For Gas Well In Carbonate Triple Media Reservoir

Carbonate gas reservoirs have always been very important in the global oil and gas resources,and the efficient development of carbonate gas reservoirs has long-term strategic significance for the protection of oil and gas supply in China.In this paper,the gas reservoir of carbonate with caved-fractured-porosity triple medium was studied.Based on the filtration theory,gas reservoir engineering theory and mathematical physics method,this paper firstly established pressure test model for triple porosity reservoir with fracture matrix and vug.And then,the production decline analysis method called normalized pressure integral and the production prediction of production were studied.The main target tasks should be accomplished in this paper are as follows:(1)First,a mathematical model for the test well of triporate-uniphase flow-parallel cross flow model without considering the effect of wellbore storage and skin factor was established.Through the Laplace transform and the Duhamel principle,the bottom pseudopressure solution with considering the effect of wellbore storage and skin factor was obtained by solving the model.Then,the pseudopressure and derivative log-log charts were drawn using program and influences were analyzed.By combining normalized pressure integral methods,we got the type curve of NPI production decline analysis method for triporate-uniphase flow-parallel cross flow model.Next step was analyzing the affecting factors of sample curve.(2)Triporate-uniphase flow-step by step cross flow model was established and solved,and the bottom pseudopressure solution with considering the effect of wellbore storage and skin factor for this model was obtained.Then,the pseudopressure and derivative log-log charts for this model were drawn using program and influences were analyzed.We got the type curve of NPI production decline analysis method for triporate-uniphase flow-step by step cross flow model by combining normalized pressure integral methods.After that,we analyzed influential factors of sample curve(3)Triporate-biphase flow model was established and solved,and the bottom pseudopressure solution with considering the effect of wellbore storage and skin factor for this model was obtained.Next,the pseudopressure and derivative log-log charts for this model were drawn using program and influences were analyzed.Besides,by combining normalized pressure integral methods,we got the sample curve of NPI production decline analysis method for triporate-biphase flow model.And then,The key factors affecting sample curve was investigated.(4)Forecasting method of production with constant rate of flow first and then constant pressure was studied with material balance method.Then the corresponding program was developed using Matlab 2014a.The key factors affecting well production was investigated using the software,such as flow coefficient,storage ratio,skin factor and dimensionless radius of well control.(5)Based on production decline method analysized in this paper,the actual production data of a production well was analyzed and the reservoir parameters were obtained.Based on the previous research on filtration theory about gas reservoir of carbonate with caved-fractured-porosity triple medium,this paper further deepens the study of gas well production decline analysis,and provides certain theoretic reference for performance prediction of gas well in carbonate formation with caved-fractured-porosity triple medium.