松辽盆地南部白垩系天然气成藏条件

应用地震、地质、地化、测井资料对松辽盆地南部进行成藏条件分析。气藏分为:下部断陷地层煤型气气藏、上部坳陷地层伴生油型气气藏、浅层生物气藏。断陷地层气藏可以分为两种类型:原生气藏与次生气藏。原生气藏分布在断陷地层内及上覆坳陷地层的底部(泉一段下部),油气成藏取决于圈闭发育状况及距源岩的远近;油气藏的保存条件取决于后期构造运动的改造程度,气层具有连片分布的特征;次生油气藏分布在坳陷地层的泉头组中上部,油气成藏取决于三个条件:圈闭发育状况,深部气源,沟通浅部圈闭与深部气源的断裂。松辽盆地南部的油型伴生气以溶解气为主,只在中央坳陷边缘部位存在气顶气藏和气藏,资源量有限。松辽盆地南部青山口组及嫩江组的成熟源岩分布有限,其丰富的生物气资源亦应作为以后的天然气勘探目标。

Accumulation and distribution conditions of natural gas from Crom Cretaceous of southern Songliao Basin

On the basis of data about seism, geology, geochemistry and well-logging, the authors analyzed the oil-gas pool forming situation in southern Songliao Basin. The results show that the gas pool was divided into three series: coal-related gas in lower fault depression, associated oil pool in upper depression and shallow biogas pool. Oil and gas pools can be divided into two kinds: the primary and the secondary oil and gas pools. The former is distributed in the fault sags and the bottom of the depression (Quan_ -1 Member of Quantou Formation, K_2q_1). Its main conditions of accumulating oil and gas pools were based on the situation of traps and the distance away from the source rocks; the retention condition of oil and gas pools depended on the degree of reconstruction in the late tectogenesis; and the gas layers had the character of regional distribution. The latter formed in the mid-upper of Quantou Formation. Its main conditions of accumulating oil and gas pools were as follows: the situation of traps, the situation of the deep gas source, and the faults connected with the upper traps and the lower gas source. The oil-gas is mainly appendix product of oil exploration in the southern Songliao Basin, most of which is solute gas, and the gas pool or pneumatic gas pool is only located at the margin of the center depression; what is more, the whole resources are limited. The mature source rocks are limited in Qingshankou and Nenjiang formations in the Southern Songliao Basin, but the rich biogas resources ought to be prospecting target in the future.