Well Test Theory Study On Fractured Wells In Tight Gas Reservoirs

As a very important unconventional oil and gas resource,tight gas can relieve the supply pressure of oil and gas,and promote the economic growth of the oil and gas industry.Therefore,the development of tight gas resources is getting more and more attention.The characteristics of tight gas reservoirs such as strong heterogeneity,low porosity,and low permeability lead to the development of tight gas reservoirs to be difficult and different compared with conventional gas reservoirs’.Therefore,we cannot directly use the conventional gas reservoir seepage theory to refer to the development of tight gas reservoirs.Although,attention has been paid to the study of tight gas reservoir seepage and well testing theory at home and abroad,there are still many deficiencies in the research at the present stage,such as consideringtoofewfactors and the model being too simple,which is quite different from the actual flow of tight gas reservoirs.Aimingatthe above problems,on the basis of extensive investigations of domestic and foreign research and in-depth analysis of the seepage mechanism of tight gas reservoirs,with consideration of stress-sensitive effect in tight gas reservoirs and non-Darcy flowin local area after fracturing,combining with various well types and fracture network,different tight gas reservoir test models have been established,and semi-analytical solutions have been carried out.Combining with computer programming,the well test curves of tight gas reservoir fractured wells(including fractured vertical wells and multi-stage fractured horizontal wells)have beendrawn and analyzed in depth.The main contents and results of this article are as follows:(1)Considering the stress-sensitive effect,well test models of fractured vertical wells in single medium,double medium and composite tight gas reservoirs have been established Among them,the establishment and analytical solution of the well test model forfractured vertical wells in composite tight gas reservoirs with consideration of stress-sensitive effect has not yet been published in other research;(2)Considering the stress-sensitive effect,well test models of multi-stage fractured horizontal wells in single medium and double medium have been established;(3)Considering the stress-sensitive effect,well test models of multi-wings fractured vertical wells in composite tight gas reservoirs has been established,which has not yet been published in other research;(4)Considering the non-Darcy flow which may occur in the near-wellbore area after fracturing,a single-medium tight gas reservoir and a dual-medium tight gas reservoir test modelshave beenestablished.This section have not yet been published in other research;(5)By the Pedrosa transformation,perturbation transformation,Laplace transformation,these models have been solved.Based on the results,the pressure and pressure derivative curves of tight gas reservoirs have been plottedusing Stehfest numerical inversion programming,and the typical curves and the effect of each parameter has been analyzed;(6)Combining with field data,the well test models established has been usedto analyze the field cases;The models presented in this paper can better describe the transient performance of fractured vertical wells and multi-stage fractured horizontal wells in tight gas reservoirs and provide more accurate and more comprehensivekinetic parameters for the development of tight gas reservoirs,and thus have an important guidance fortight gas reservoirs development.