中国古生界海相地层油气勘探

影响中国古生界海相油气勘探并且需要加强研究的主要问题是:保存条件的认识与有利区预测;有效烃源岩与资源潜力;储层的复杂性及其对非构造圈闭的影响。保存条件分为三个层次:含油气盆地的保存、含油气系统的保存、油气藏的保存。塔里木、四川、鄂尔多斯三大克拉通盆地是中国古生界保存较好的盆地,是海相油气勘探的战略目标区,另外还有准噶尔、楚雄等盆地。盆地斜坡相泥岩及泥状灰岩是海相油气勘探的主要烃源;海陆过渡相烃源岩发育区是重要战略方向;陆表海碳酸盐岩烃源岩区是中小油气田勘探领域。从储层条件来说,下古生界应以非砂岩岩溶储层为主要勘探对象,溶蚀不整合面广泛发育,已发现的下古生界大中型油气田仅见于碳酸盐岩溶储层;上古生界以孔隙性碎屑岩及碳酸盐岩储层为主要勘探对象,晚古生代的构造一古地理演化为这两类储层的广泛发育提供了条件。

Petroleum Exploration on Paleozoic Marine Strata in China

The petroleum exploration of the Pareozoic marine Strata is pessimistic “chicken rib” or optimistic replacing domains for China in the future?It is an important problem faced by China's explorers.The exploration experiences in the past five decades have proved that objective factors for restricting the petroleum exploration are multiple tectonic movements,dis- cussible resource rock criterion,complicated reservoir rocks and tight cap wanted.And the subjective factors are explo- ration technology development,geology cognition,exploration investment and so on.It is considered that Paleozoic marine strata will be one of the main exploration domains in 21 century after analyzing the favorable areas and resources potentialities in the light of petroleum geological particularities.According to the restrict factors and particularities mentioned above,some principles should be followed for selecting favorable exploration areas;a)Large stable rudimental blocks after last hydrocar- bon trapping,b)Favorable tectonic locations for forming source rocks,such as rift basins,aulacogens and their mar- gins.c)Favorable sedimentary facies such as the lower Pale- ozoic nonsandstone reservoirs,especially karst reservoirs re- lated with unconformity,and the upper Paleozoic sand reser- voirs or porous carbonate reservoirs,d)Strata,lithology or structural trap types under the paleo-uplift background,e)Un- conformity interfaces,large sand bodies and convergent zones of fractures as main migrating ways.It is suggested that Tarim,Ordos and Sichuan craton basins are the strategic ex- ploration regions where Paleozoic marine strata are well pre- served.The slope facies mudstones are the main source rocks for the marine strata.The areas where there are marine/conti- nental transitional facies source rocks are the important explo- ration targets.The areas where there are epicontinental sea facies carbonate rocks are the domains for seeking middle and/or oil fields.As for reservoir condition,the exploration target of the lower Paleozoic strata should be karst reservoirs of nonsandstone as the discovered large and/or middle fields are only lower Paleozoic carbonate karst reservoirs.The target of the upper Paleozoic strata should be porous clastic rocks and carbonate reservoirs as late Paleozoic tectonic and paleo- geographical evolvements supplied conditions for the wide de- velopments of the two kinds of reservoirs.