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将致密砂岩气聚集带划分为连续带和过渡带,并建立相应的地质模型。连续带位于构造低部位或斜坡处,砂岩直接覆盖在烃源岩之上,具有天然气大面积连续分布,上部不受盖层控制,下部无明显底水等特点;过渡带紧邻连续带,位于斜坡的上倾方向或构造较高部位,砂岩与烃源岩没有直接接触,天然气主要分布在储层物性相对较好的“甜点”中,天然气藏具有常规气和连续气2种特点。连续带以纳米级孔喉结构为特征,天然气运聚主要驱动力为生气产生的超压;过渡带以微米级孔喉结构为特征,天然气运聚主要驱动力为浮力。基于上述认识,建立“排挤式”和“置换式”致密砂岩气聚集数值模型。该模型在四川盆地合川地区的应用效果符合率达到90%,指出还有一半的天然气资源未被发现,主要分布在合川地区东北部、潼南地区北部和潼南地区东南部。
The tight sandstone gas accumulation zone is divided into continuous belt and transition zone, and the corresponding geological model is established. The continuous belt is located at the lower part of the structure or slope. The sandstone directly overlies the source rock with the continuous distribution of a large area of natural gas, the upper part is not under the control of the cap rock and the bottom has no obvious bottom water. The transition zone is adjacent to the continuous belt and is located on the slope , And the sandstone does not directly contact with the source rock. Natural gas is mainly distributed in sweet spots with relatively good reservoir properties. Natural gas reservoirs have two characteristics: conventional gas and continuous gas. The continuous belt is characterized by nanoscale pore-throat structure. The main driving force of natural gas migration and accumulation is overpressure caused by gas generation. The transition zone is characterized by micron-scale pore-throat structure. The main driving force for natural gas migration and accumulation is buoyancy. Based on the above understanding, numerical models of tight sandstone gas accumulation with “crowded” and “permutation” are established. The coincidence rate of application of this model in Hechuan area of Sichuan Basin reached 90%, indicating that half of the natural gas resources have not been found. They are mainly distributed in the northeastern Hechuan area, the northern part of Tongnan area and the southeast of Tongnan area.