盖层封闭天然气藏定量评价模型

Quantitative Evaluation Model of Gas Sealing Ability of Cap-rock

为了定量评价盖层封闭天然气性能,分别建立了散失过程开始、封闭气柱最大高度、突破时间、逸散速率等指标的数学模型。依据东营凹陷深层泥岩实际地质资料,利用测井资料拟合出经验公式用以求取封盖参数;综合考虑盖层固有封盖性能、盖层阻滞天然气通过的阻力与气藏驱动力之间的差值、天然气突破时间与气藏成藏时间对比等因素,对东营凹陷沙一段和沙三中、下亚段泥岩盖层封闭性能进行了评价,结果表明沙一段盖层封闭天然气最有利地区为民丰洼陷,利津洼陷、博兴洼陷沙一段盖层不利于天然气的保存成藏;沙三中、下亚段泥岩盖层封闭性能较好的区域分布于利津洼陷、民丰洼陷,其次为牛庄洼陷。

In order to quantitatively evaluate the cap-rock sealing ability,some mathematic models were established which included the indexes of the beginning of effusion,the highest gas column,breakthrough time and effusion rate.According to the theoretical analysis and measured data in Dongying Depression,empirical formula was obtained for deriving sealing parameters with the highest amount by using the geological data of deep layer mudstone and logging data of Dongying Depression.The factors of natural sealing performance of the cap-rock,the difference between its resistance and driving force of gas reservoir and the comparison between breakthrough time and reservoir forming time were comprehensively considered,the mudstone cap-rocks of Es1 and middle and lower members of Es3 were evaluated.The results show that the best area of mudstone cap-rock of Es1 is Minfeng Depression but the worst ones are Lijin Depression and Boxing Depression; the best ones of members of Es3 are Lijin Depression and Minfeng Depression ,the next is Niuzhuang Depression .