Reservoir Characteristics and Exploration Implications of Gas Hydrate Enrichment Area,Qiongdongnan Basin
Gas hydrate is an important development of marine new energy,and the Qiongdongnan basin of the South China Sea is a hydrate enrichment and hot research area.In order to further understand hydrate reservoir characteristics of the Qiongdongnan area,thermal insulation and pressuring coring sampled by domestic technical equipment were selected for analysis and first-hand data were obtained.By comprehensive analysis of grain size,rock and mineral analysis(including electron microscope scanning),LWD,thermal imaging,chloride ion saturation method,etc.,it is measured that the reservoir is mainly composed of siliceous and aluminous clay deposits composed of quartz(23%content),plagioclase(17%content),sericite(15%content),albite(14%content),etc.,and the median grain size of reservoir is 15.1 μm to 34.1μm and the saturation distribution is 3%to 54%.It reveals six characteristics of hydrate reservoir:"fine-grained,unconsolidated,easily disintegrate and disperse,high resistance,high acoustic velocity,and strong heterogeneity".Combined with gas source,reservoir analysis and exploration knowledge,a reservoir formation model of"off-site thermogenic gas injection,local microbial gas supplement,accumulation at top of gas chimney,and horizontal formation in the submarine fan reservoir"has been established.Focusing on the X-ray and CT scanning of 123 mbsf and 153 mbsf in-situ pressure-retaining cores,two main types of reservoirs are identified:argillaceous silt pore-type reservoir(submarine fan)and argillaceous silt micro-fractured reservoir(gas chimney fluid reconstruction),a new discovered type of hydrate reservoirs in the South China Sea.Exploration inspirations are put forward,"study the occurrence and resource potential of shallow scaled sand-bodies of geological events in the Zhujiangkou and Qiongdongnan sea,and strengthen research on heat and mass transfer of reservoir formation mechanism and resource evaluation".The research will provide important scientific reference for hydrate research and production test of the South China Sea.
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