松辽盆地南部十屋断陷天然气成藏条件定量研究

天然气成藏条件定量研究,实际上就是运用天然气成藏的聚散动平衡理论,对天然气的生气量、运移量、散失量和聚集量进行定量的研究.天然气能否成藏,取决于天然气的聚散动平衡.当天然气聚集量大于散失量时,气藏就能形成;反之气藏就不能形成.这种动平衡关系必须是在定量研究的基础上才能体现出来.松辽盆地是我国最大的陆相含油气盆地.盆地南部天然气资源应是相当丰富,但天然气勘探目前仍未获突破,一个重要原因就是勘探思路受"背斜"论严重束缚,对天然气成藏的定量研究太薄弱.运用天然气的聚散动平衡理论,以松辽盆地南部十屋断陷为研究对象,应用新的地质模型及相应的数学模型,模拟计算了十屋断陷西部的生气量、排气量、残留量、渗流(漏)量、扩散量,得出了可能的最大聚集量.研究结果表明,该区是一个生气量很大的地区,但区域内构造高点上是一个保存条件较差的残留气田,今后应将十屋断陷勘探重点向构造翼部和深凹鞍部等相对低部位转移,开展非构造油气藏的研究与勘探.依据该研究成果部署的松南76井,获得稳产天然气13×104m3/d的高产商业气流,并发现了松辽盆地南部最大的天然气田--孤家子气田.研究实践证明:在松辽盆地南部地区,构造斜坡和鞍部的低幅度构造-岩性圈闭可以形成优于构造高点的高产油气田(藏).在今后油气勘探中,应该对占该区总面积70%的尚未钻探的斜坡和向斜等非构造领域进行重新评价研究.图3参4 (孙大明摘)

A Quantitative study on formation of gas pool in Shiwu fault depression of Songliao basin

The main method of quantitative study on formation of gas pool is the quantitative modelling of gas generation, migration, dispersion, and accumulation. Whether a hydrocarbon pool can form or not depends on its dynamic-equilibrium of accumulation and dispersion. If gas accumulation volume is greater than its dispersion amount, gas pool will form. On the contrary, it will not. Songliao basin is the largest continental-petroliferous basin of China. Based on a large amount of geological, geochemical, geophysical and engineering data on Shiwu fault depression of Songliao basin, studies of regional structure evolution, fault distribution, characteristics of depositional stratigraphy and trap characters of source rock, reservoir rock, cap rock and gas migration as well as their simulation matches are conducted in the paper. On the basis of these above, the quantities of gas generation, residue, diffusion, dispersion and accumulation are calculated by the means of new geological modelling and relevant mathematical modelling. From these results, we can get the possible largest accumulation quantity. The results of modelling confirm that gas pool at the regional structural high is a residual gas field, the amount of gas generated is large, but preservation condition is poor. From now on, the focal point of prospecting would be searching for various low-relief structural-lithologic gas pools, so that the study and prospecting of stratigraphic traps in lower places should be strengthened.