Reservoir Characteristics And Favorable Zone Prediction Of The Majiagou 5^th Formation Of Ordovician In X-zone Of Jingbian Gas Field

In this paper,the X-area of Jingbian gas field is taken as the research block and regard the Ordovician weathering crust and the carbonate reservoir in Majiagou 5^th Formation as research object.Using drilling and logging data in the study area,analysis of core,thin sheet observation,physical properties,gas test,etc to combine geological theory with exploration practice for in-depth study on the reservoir characteristics respectively of the Ordovician Majiagou 5^th Formation in the X area of Jingbian gas field.Therefore summarise the main controlling factors of natural gas accumulation in the study area with the Ordovician Majiagou 5^th Formation stratigraphic division,sedimentary facies division,karst paleogeographic remodeling,petrological characteristics,diagenetic characteristics,reservoir pore characteristics and spatial characteristics.It has determined the carbonate reservoir of the Ordovician Majiagou 5^th Formation in the study area as the evaporative tidal phase according to the lithological distribution;established a complete tidal-intertidal-tidal full rotation mode;divided the sedimentary microfacies of the Ordovician weathering crust to eight main microfacies types;reshaped the paleo-karst geological model into a three-stage model of interlayer karst,weathering crust karst and fracture-cavity karst,which lays a theoretical foundation for predicting favorable reservoir zones.On the above basis,describe the petrological characteristics of the Majiagou 5^th Formation,the diagenesis and diagenetic facies of the Ordovician weathering crust were determined and conclude the pore characteristics of the reservoir in the study area based on the observation of thin slices.At last,revealing the main controlling factors of natural gas accumulation in the study area by superimposing various geological features.Analyze the favorable development interval of the reservoir and further predict the favorable area: the favorable exploration area of Jingbian gas field is the rolling exploration favorable area of Jingbian karst platform,Gila-Zhaohuang Temple-Ang Su Temple karst saddle valley favorable exploration area,dissolution plateau favorable exploration area in the eastern part of X area,the southern part of the Yulin-Yanchuan karst plain exploration prospect area.