综合地化、储层、地震、测井、测试等相关资料,详细调查了莺歌海盆地坳陷斜坡带乐东峡谷水道已发现气藏特征及成藏关键地质因素,结果表明:该区中新统气藏具有“三低一高”(低孔、低渗、低含气饱和度及异常高压)和流度低的特点,类似于高温高压的致密砂岩气藏.坳陷斜坡具有形成低孔低渗砂岩气藏的有利条件:①发育高成熟富陆源有机质的中新统烃源岩及渐新统崖城组合煤烃源岩,烃源条件好;②中新统三角洲及水道-海底扇砂岩受强烈压实作用以及钙质胶结的影响,具低孔特低渗特征,分布较广且厚度大,构成了天然气的重要聚集场所;③天然气通过隐伏断裂沟源+接触式充注,“甜点”储层富集成藏.初步预测坳陷斜坡带南段具备千亿立方米以上天然气储量规模,勘探潜力大.%This paper,through comprehensive analysis on geochemical,reservoir,seismic,well logging and formation testing data,investigated characteristics of the gas reservoirs discovered in Ledong area channel fillings on the depression slope belt,Yinggehai basin and its geological conditions of gas accumulation.The result shows that the Miocene gas reservoir in this zone has characteristics of "three low (low porosity,low permeability,low gas saturation) & one high (abnormal overpressure)" and slow fluidity,which is similar to the features of tight sandstone gas reservoir with high pressure and high temperature.Available data indicate that the zone is of the conditions beneficial to the formation of low porosity and low permeability gas reservoirs:① there are terrigenous organic-rich Miocene source rocks and Oligocene Yacheng coal-bearing source rocks with high thermal evolution degree,supplying abundant gas;) the Miocene delta and channel-submarine fan sandstone reservoirs experienced strong compacting action and calcite cementing,and formed the features of low porosity and ultralow permeability,with large gross thickness of sand bodies and wide distribution,which offered important space for gas accumulation;③ gas migrated into reservoir through pathways of "hidden fault" and contact-type charging,and reservoir "sweet spots" are more favorable for gas accumulation.Preliminary study results reveal that the southern section of the depression slope zone has relatively great exploration potential with the gas reserve exceeding 100 billion cubic meters.
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