| The static connectivity of sandstone carrier bed is the frontier and weak link of current sedimentary disciplines.Its connectivity affects oil and gas migration path and zone characteristics,and is a key factor in controlling oil and gas distribution.The Qijia area is located in the northern part of the Qijia-Gulong sag in the Songliao Basin,the destination horizon is the Gaotaizi oil layer with simple structure and poor fault development,the sandstone carrier bed constitutes the main path for hydrocarbon migration.The Gaotaizi oil layer in Qijia area is a large-scale outside source rock and simple slope sandstone carrier bed transport system.To clarify the control effect of static connectivity of the Gaotaizi reservoir sandstone carrier bed on oil and gas distribution in Qijia area,the relevant predecessor research results are fully investigated,core,logging,outcrop data,modern sedimentation and 3D seismic data are comprehensively used,and the hydrocarbon accumulation theory and percolation theory are guided for this study.Firstly,single sandstone carrier bed were divided based on the high-frequency sequence evolution.Secondly,based on phase-controlled three-dimensional stochastic geological modeling technology,the key threshold of net to gross of static connectivity of sandstone carrier bed are defined,and a set of sand body static connectivity characterization method based on sedimentary environment,evaluation scale,sand body geometry and net-to-gross is formed.Finally,the control of the static connectivity of sandstone carrier bed on oil and gas distribution is summarized,and the favorable target zones of oil and gas distribution in different sandstone carrier bed are predicted.The paper has mainly achieved the following research results:(1)The Gaotaizi oil layer in Qijia area is dominated by sub-facies of delta-wave common-controled delta fronts.The types of microfacies are mainly underwater channels,mouth bar and sand sheet.The width of the underwater channels is concentrated in the range of 50?250m,the thickness range 2.5m to 5m,width-to-thickness ratio range 20?90;mouth bar sand body width range 200?5000m,length range 250?15000m,thickness range 2?6m,length-width ratio range 1.2?3,sand sheet thickness range 1?5m,area range 0.05km~2?50km~2.(2)It is recognized that there are 4 sets of single sandstone carrier bed in the G?group to the GIV group in Qijia area,they are upper GIII group sandstone carrier bed(G?1?G?12),lower GIII group sandstone carrier bed(G?13?G?23),upper G?group sandstone carrier bed(G?1?G?7)and lower G?group sandstone carrier bed(G?8?G?18),and each single sandstone carrier bed uses the regional lake intrusive rocks as the top and bottom plate interface.(3)The control factors of static connectivity of sand bodies are clarified,and it is recognized that the static connectivity of sandstone carrier bed is mainly controlled by net-to-gross ratio,and also affected by sedimentary environment,evaluation scale and sand body geometric parameters,and the characterization method of sand body static connectivity based on the above four factors was formed,and the initial connectivity threshold and complete connectivity threshold of net to gross of different sedimentary environments under zone evaluation scales were determined.Among them,the inner delta front subfacies are 0.1 and 0.5,and the outer delta front subfacies are 0.05 and 0.4.(4)Clarified the favorable oil and gas zones in the large-outside simple slope area,it is proposed that the oil and gas are mainly distributed in the zone between the initial connectivity threshold and the complete connectivity threshold of the single sandstone carrier bed in the Qijia area,the distribution of oil and gas in each single sandstone carrier bed is predicted,and four favorable zones are proposed. |
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