烃浓度封闭及其在盖层封盖天然气中的重要作用

HYDROCARBON CONCENTRATION SEALING AND ITS IMPORTANT ROLE IN SEALING GAS OF CAPROCKS

烃浓度封闭是与毛细膏封闭和扭压封闭截然不同的盖层封油气机理，它虽不能对呈游离相和水溶相运移的天然气构成封盖，却可以阻滞呈分子相扩散运移的天然气，对天然气聚集与保存具有重要意义。根据地层纵向剖面中天然气在水中的浓度变化情况，提出了盖层烃浓度封闭天然气的３种模式，即无烃浓度封闭模式、部分烃浓区封闭模式和完全烃浓度封闭模式，并将其应用于松辽盆地三肇地区青山口组泥岩盖层对下伏扶余油层天然气扩散运移的浓度封闭作用的研究中，结果表明青山口组泥岩盖层在该区对扶余油层中天然气具有完全烃浓度封闭作用，凹陷中心最强，向四周减弱，充分表明了烃浓度封闭在盖层封闭天然气中的重要作用。

Hydtocarbon concentration sealing is an obviously different sealing mechanism withcapillary sealing and pressure sealing,it can not seal the gas in free and water-dissolvedphase, but it can seal the gas in diffusive phase,It is of the important significance for gas toaccumulate and Conserve. Based on the gas-bearing concentration change in the stratigaphicwater along the vertical section,this paper put forward three kinds of hydrocarbon concen-tration sealing medels:non-hydrocarbon concentration sealing model,partly hydrotrationconcentration sealling rnodel and completely hydrocarbon concentration sealing model,andused it in studying the hydrocarbon concentration sealing cf mudstone caprock of Qing-shankou Formation to the diffusive migration of gas from Fuyu oil layer in Sanzhao region ofSongliao dssin, The result indicates that mudstone caprock of Qingshankou Formation ownscompletely hydrocarbon concentration sealing to the gas of Fuyu oil layer in Sanzhao region,its sealing abilty is the strongest in the centre of depression and begins to decrease from thecentre of depression to its-surrounding area. This fully indicates that hydrocarbon concentra-tion sealing plays an important role in sealing gas of caprocks。