渤海湾盆地黄骅坳陷板桥凹陷深层低渗透(致密)砂岩气藏充注特征及成藏过程

渤海湾盆地深层发育大量的低渗透(致密)砂岩气藏,但是有关深层低渗透(致密)砂岩气藏的充注特征和成藏过程缺乏系统的研究。文章以板桥凹陷为例,综合利用测井、岩心、地震和分析化验等资料,从油气的来源入手,分析天然气的充注通道、动力和阻力的关系,探讨充注方式,同时结合流体包裹体的系统测试分析,探讨了板桥凹陷深层低渗透(致密)砂岩气充注特征及成藏过程。研究结果表明,板桥凹陷深层天然气主要为凝析油伴生气和煤型气的混合气,来自于成熟-高成熟演化阶段的沙三段烃源岩。依据烃源岩和储层的空间配置关系,深层天然气的源储结构主要为源储一体型、源储相邻型和源储分离型3种类型。深部砂层中的孔隙和裂隙以及断裂均可以构成深层天然气充注的通道,天然气的充注动力比较大,其中源储一体型在7.80～7.95 MPa,源储相邻型和源储分离型在4.80～9.55 MPa。断裂带的排替压力分布在3.14～7.05 MPa,砂层排替压力分布在0.01～0.29 MPa,充注动力均大于断层的排替压力和砂层的排替压力。源储一体型中的深层天然气第一种充注方式为由烃源岩直接向砂层充注,第二种充注方式为首先通过断层垂向运移,然后再向相连的砂层...

Charging characteristics and accumulation process of deep low-permeability (tight) sand gas reservoirs in Banqiao Sag,Huanghua Depression

A large number of deep low-permeability (tight) sand gas reservoirs are discovered in the Bohai Bay Basin, but the systematic investigation of hydrocarbon charging mechanism and accumulation process related to those reservoirs is rarely seen.The study investigates the Banqiao Sag by analyzing genetic affinities among gas samples at first, and then the relationship between the charging path, dynamics and resistance, as well as discussing the charging patterns by using a series of data, including logging, core observation, seismic surveys, tests and analyses.Meanwhile, combined with the systematic test and analysis of fluid inclusions, the charging characteristics and accumulation process of deep low-permeability (tight) sand gas in Banqiao Sag are discussed.The results show that gases in the study area are primarily a mixture of condensate oil associated gas and coal-derived gas from the 3rd member of Shahejie Formation (Es³) at mature to high-mature stages.According to the spatial distribution patterns between source rocks and reservoirs, the source-reservoir assemblages can be classified into three types, namely, the united source-reservoir type, the adjacent source-reservoir type and the separated source-reservoir type.The networks of pores, fractures and faults in the deep sand beds constitute the pathways for gas charging.The charging dynamics of deep natural gas is greater than the displacement pressure of faults and sand beds with 7.80-7.95MPa for the united source-reservoir assemblage, and 4.80-9.55 MPa for the last two.Whereas the displacement pressure of fault zones and sand beds ranges from 3.14 to 7.05 MPa, and from 0.01 to 0.29 MPa respectively.There are two kinds of charging patterns for the first assemblage:the first one is that the gas can be charged directly to the sand beds through the source rocks, the primary mode for the united source-reservoir type; the second one is that natural gas has sufficient dynamic to migrate upward through faults, and then can be migrated laterally in the upper sand beds, the main mode for the last two.In addition, the multi-stage and dynamic accumulation process of the deep gas reservoirs in Banqiao Sag is described as "two stages of oil charging, that is, oil charging before gas charging, a dominant pattern in the late period", which results in a distribution of "upper petroleum and lower gas vertically, and hydrocarbon accumulation near faults".