| Gujiazi gas field is located in Gujiazi Township,Lishu County,Jilin Province.It is a anticline located in the southwest of central structural belt of Shiwu fault depression.The structure is divided into three fault block including Gudong,Guzhong,and Guxi by four west dipping faults and one east dipping falut.The main gas-bearing interval including Nong IX to Nong XI?Xiao I to Xiao III.Sand body is typical low porosity,low or extremely low permeability reservoir.Since the development of the field in 1996,it has been developed in the late stage of development with high producing reserves,outstanding well condition problems and poor well patten adaptability.Based on the detailed description of the gas reservoir,a geological model is established by the method of combining dynamic and static parameters and the precision of the model is verified by linear fitting.The dynamic reserve calculation method of low permeability gas reservoir is considered by analyzing the difference of production capacity and water flooding law.This paper deduces the reasonable spacing between two fracturing wells,and describes the principle of residual gas distribution in order to improve the recovery of gas field.The paper research results in the following results:(1)Through a small layer correlation and research of sedimentary facies,puts forward that Gujiazi gas field's main gas-bearing section is in delta sedimentary system,subordinate to the sedimentary microfacies are underwater distributary channel of the delta front,mouth bar and front delta mud deposits.(2)Due to the influence of natural fracture development and reservoir fracturing,logging permeability has some error and cannot be directly used in the fine modeling of gas reservoir.On the basis of gas reservoir description,the paper puts forward some methods to constrain the model like correcting logging permeability,additional dynamic analysis results of low permeability gas reservoir.The linear fitting accuracy of this model is significantly higher than the conventional static model and the success rate of history matching can reach 53.8%.(3)Without considering the effect of slippage effect,stress sensitivity and start-up pressure gradient factor,traditional low permeability gas reservoir dynamic reserve calculation has its limitation.This paper built a capacity formula considering the combined impact of these factors,derived the relation to the material balance equation,fitted the bottom hole pressure and the volume of gas production,and determined the reasonable dynamic reserve calculation method for low permeability gas reservoir.This method has solved the limitation of small amount of pressure data of the gas field by converting formation pressure into bottom hole pressure.The research shows that the dynamic reserves of low permeable gas reservoirs decrease with the increase of start-up pressure gradient and stress sensitivity.(4)The distribution of pressure gradient can determine the drive area ratio,effective flow radius ratio and effective pressure gradient ratio in the flow unit,derive the relationship between pressure gradient and the start-up pressure gradient in the streamline field,establish the calculation method of reasonable well spacing calculation for low permeability gas reservoir natural energy development.The research shows that the reasonable well spacing between the two fracturing gas wells increases with the increase of production pressure difference,and the larger the effective flow,the smaller the reasonable well spacing.Based on the research of the law of residual gas distribution,the method to calculate rational well spacing of low permeability gas reservoir fracturing wells can be applied to the Gujizi gas reservoir,and it can provide the basis for the deployment of new fracturing wells in the gas enrichment area. |
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