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天然气的成藏过程是指天然气从源岩排出后的运移、聚集和散失过程,这一过程的有效性可以用气藏成藏保存阶段单位圈闭面积内的充注速率与散失速率的差值,即天然气净聚集速率定量表征。根据净聚集速率的高低,可将天然气成藏过程的有效性划分为高效、中效和低效3个级别。根据对典型气藏的解剖和大量气田的统计,天然气成藏过程的有效性主要受气藏成藏期源储剩余压力差、输导体系的类型和输导效率、盖层的厚度和排替压力3方面因素的控制。在我国含油气盆地的地质条件下,中、高效成藏过程的的主要地质条件是天然气成藏期的源储剩余压力差大于25MPa,具有汇聚型输导体系,气藏盖层厚度大于40m和排替压力大于15MPa。利用上述指标可以对盆地范围内天然气成藏过程的有效性进行定量或半定量评价和预测高效气藏的分布。
The process of gas accumulation refers to the process of migration, accumulation and dissipation of natural gas after it is discharged from the source rock. The validity of this process can be expressed as the difference between the filling rate and the rate of loss within the trap area per unit area Value, which is the quantitative characterization of the net rate of natural gas accumulation. According to the net aggregation rate, the effectiveness of natural gas accumulation can be divided into three levels: high efficiency, medium efficiency and low efficiency. According to the anatomy of typical gas reservoirs and the statistics of a large number of gas fields, the effectiveness of natural gas accumulation process is mainly affected by the residual pressure difference of source reservoirs during reservoir formation, the type of conductivity system and conductivity, the thickness of caprock and displacement pressure 3 factors control. Under the geological conditions of petroliferous basins in China, the main geological conditions for medium and high-efficiency hydrocarbon accumulation processes are that the residual pressure difference between source and reservoir during natural gas accumulation period is more than 25MPa, with convergent conductivity system, the cover thickness of gas reservoir is more than 40m and Replacement pressure greater than 15MPa. The above indexes can be used to quantitatively or semi-quantitatively evaluate the effectiveness of natural gas accumulation in the basin and predict the distribution of high-efficiency gas reservoirs.