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四川盆地缝洞型碳酸盐岩气藏多属于有水气藏,气水两相渗流机理复杂。目前气水两相微观渗流可视化模型多是基于理想孔隙结构或铸体薄片图像制作,无法还原储层中真实孔、缝、洞分布,且机理研究多集中于孔隙型和裂缝型储层,缺少对孔洞型和缝洞型储层的认识。通过将岩心CT扫描与激光刻蚀技术结合,以四川盆地震旦系储层中裂缝型、孔洞型和缝洞型碳酸盐岩岩心CT扫描结果为模板,设计并研制了3类岩心的可视化模型,据此研究了气水两相微观渗流机理及封闭气、残余水形成机理,通过Image J灰度分析法实现了气水分布的定量表征。研究结果表明:3类模型水驱气和气驱水过程中的渗流规律各不相同;绕流、卡断、盲端和角隅处形成的封闭气普遍存在于3类模型中,此外还在“H型”孔道处、“哑铃型”通道处和微裂缝缝网处形成特殊封闭气;孔道、裂缝壁面上的束缚水膜,溶洞中部的圆润水团,狭窄喉道处的卡断水柱和狭长孔道处的滞留水柱是残余水的主要形式;裂缝型模型水窜最严重,无水采收期最短,采出程度最低,而孔洞型模型水驱前缘推进均匀,无水采收期最长,采出程度也最高。该研究实现了对缝洞型碳酸盐岩不同类型储层气水两相微观渗流规律的精准刻画,为类似气藏的高效开发提供了理论依据。
Most of the fractured-hole carbonate reservoirs in Sichuan Basin belong to a gas reservoir, and the mechanism of gas-water two-phase seepage is complex. At present, most of the visualization models of gas and water two-phase micro-seepage are based on the ideal pore structure or casting sheet images, and can not restore the true distribution of holes, seams and holes in reservoirs. The mechanism studies mostly focus on pore-type and fracture-type reservoirs, Knowledge of hole type and fracture-cavity type reservoir. Through the combination of core CT scanning and laser lithography techniques, three types of core visualization were designed and developed based on the CT scanning results of fractures, vugs and fractured-hole carbonate cores in the Sinian reservoir in the Sichuan Basin Model, the micro-seepage mechanism of gas-water two-phase flow and the mechanism of formation of closed gas and residual water were studied. The quantitative characterization of gas-water distribution was achieved by Image J grayscale analysis. The results show that the seepage laws of water flooding and gas flooding are different in the three models. The closed gas formed around the flow, stuck off, blind end and corner is commonly found in three kinds of models, “H-type” channel, “dumbbell-type” channel and micro-crack seam network to form a special closed gas; channel, the bound water film on the crack wall, the cave in the middle of the round water, the narrow throat card The water column at the water column and the narrow channel is the main form of residual water. The water channeling of the fractured model is the most serious with the shortest water recovery period and the lowest recovery rate. The water front of the water hole model is even, The longest receipt, mining the highest degree. The study realizes the precise characterization of micro-seepage law of gas and water in different types of reservoirs of fractured-cavity carbonate rocks and provides a theoretical basis for the efficient development of similar gas reservoirs.