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在对低孔渗大气区地质特征、控制因素分析的基础上,剖析了不同类型气藏的形成机制.低孔渗砂岩连续型大气区的主要地质特征表现在:大范围、低丰度、连续分布、大气区的天然气聚集特征;广覆式优质烃源岩与紧密接触式生储盖组合;主要发育于大型陆相坳陷或海陆交互相浅水河流三角洲体系;大范围准层状岩性型、成岩型和毛细管压力型为主的多种圈闭类型共生;存在达西流和非达西流双重渗流机理;多种类型气水关系并存,气水分布复杂化;甜点高产、带状富集、宏观连片的资源分布规律.低孔渗砂岩大气区形成的主要控制因素是:稳定的动力学背景和平缓的构造格局控制广覆式砂泥岩大范围交(间)互分布;大型缓盆弱水动力条件控制大范围浅水三角洲连续性低孔渗储层的形成;区域性差异成岩作用和非均一性成岩相控制有利储层和成岩圈闭群的发育;弱小弥散的成藏动力导致大范围连续分布的气藏资源丰度低.不同圈闭类型的低孔渗砂岩大气区具有不同的成藏机制:岩性圈闭气藏的分隔式压差交互机制;成岩圈闭气藏的分流式差异汇聚机制;毛细管压力圈闭气藏的非达西渗流机制.研究结果对深化和完善我国天然气地质理论,实现低孔渗天然气的预测评价和有效勘探具有一定的实践意义.
Based on the analysis of the geological characteristics and control factors in the low permeability air zone, the formation mechanism of different types of gas reservoirs is analyzed. The main geological features of the continuous atmospheric zone with low porosity and permeability are as follows: large-scale, low-abundance, continuous Distribution and atmospheric zone. The broad-cover high-quality source rocks are combined with close contact type reservoirs and caprocks. They are mainly developed in large continental depressions or deltaic system of shallow water rivers with sea-land interaction. Large-scale quasi-stratiform lithology , Diagenesis and capillary pressure type symbiosis; there are Darcy flow and non-Darcy flow dual seepage mechanism; the coexistence of many types of gas and water, gas and water distribution complex; dessert high yield, banded And macroscopical contiguous resources.The main controlling factors for the formation of the low-porosity sandstone atmosphere are: steady dynamic background and gentle tectonic setting to control the inter-distribution of widely distributed sand-shale rocks; Basin weak hydrodynamic conditions control the formation of a continuous low porosity and permeability reservoir in a wide range of shallow water delta; regional differential diagenesis and heterogeneous diagenetic facies control the development of favorable reservoirs and diagenetic trap groups; weak The accumulative motivation of scattered formation leads to low abundance of gas reservoirs with a large range of continuous distribution.The different trap types of low porosity and permeability sandstone have different gas accumulation mechanisms in the atmosphere: compartmentalized differential pressure interaction mechanism of lithologic trap gas reservoir, diagenesis Shunting differential convergence mechanism of trapped gas reservoirs and non-Darcy seepage mechanism of capillary pressure trapped gas reservoirs.The results of this study have certain practical significance for deepening and perfecting the geological theory of natural gas in our country and realizing the prediction and evaluation of low porosity gas and effective exploration.