超压泥岩盖层封闭水溶相天然气能力的评价方法

A method for evaluating sealing ability of over-pressured mudstone caprock for gas in water-dissolving phase

在分析泥岩超压形成机制及条件的基础上,研究其水溶相天然气的封闭机理,得到超压泥岩盖层主要依靠下致密层的吸附阻力封闭水溶相天然气,超压不能对水溶相天然气直接封闭,但超压值可以反映超压泥岩盖层最低的封闭水溶相天然气能力.利用超压值及空间分布,可以定量评价超压泥岩盖层对水溶相天然气最低的封闭能力及空间分布.将此评价方法应用于大庆长垣以东地区青山口组超压泥岩盖层对水溶相天然气的最低封闭能力的评价,得到该区青山口组泥岩盖层对水溶相天然气具有好的最低封闭能力,有利于该区扶余和杨大城子油层水溶相天然气聚集与保存,这是扶余和杨大城子油层能找到大量天然气的一个重要原因.

Based on the analysis of formation mechanism and conditions of overpressure of mudstone,the seal mechanism of over-pressured mudstone caprock for gas in water-dissolving phase was studied.Gas in water-dissolving phase was considered to be sealed by adsorptive force of lower tight layer.Overpressure can't seal gas in water-dissolving phase directly,but it can reflect the minimum sealing ability of over-pressured mudstone caprock for gas in water-dissolving phase.The method was applied in evaluating the minimum sealing ability of Klqn over-pressured mudstone caprock for gas in water-dissolving phase in Daqing Placanticline and its east.Klqn over-pressured mudstone caprock was considered to have minimum sealing ability for gas in water-dissolving phase in most of Daqing Placanticline and its east.It is favorable for gas in water-dissolving phase to accumulate and preserve.It is one of the important conditions that a lot of gas reservoirs can be found in F,Y oil layers of Daqing Placanticline and its east.