中国海相碳酸盐岩层系油气勘探特殊性问题

中国至少有3 0 0×1 08t的海相碳酸盐岩油气资源量,是十分重要的勘探领域。在近5 0年的勘探历程中虽有塔河、普光等碳酸盐岩大油气田的发现,但探明储量仍然很低,这与勘探投入低有关,但更主要的原因在于中国海相碳酸盐岩油气地质的特殊性。经研究其特性可概括为7个方面:(1)碳酸盐岩层系形成于多旋回的叠合盆地;(2)碳酸盐岩层系时代老,埋藏深;(3)烃源岩具有多元、多期生烃;(4)储集层类型多、非均质性强;(5)圈闭类型多样,以隐蔽圈闭和复合圈闭为主;(6)油气藏改造、破坏严重,保存条件复杂;(7)油气藏分布复杂,预测难。要尽快实现碳酸盐岩油气探明储量的快速增长,缓解国内油气资源供需矛盾,必须加强碳酸盐岩油气富集与分布规律的理论研究和勘探技术攻关。文中将中国海相碳酸盐岩油气富集理论的研究凝练为三个方面的科学问题:(1)海相碳酸盐岩层系发育环境、构造演化及其对有效烃源岩的控制作用;(2)海相碳酸盐岩介质油气运聚机理;(3)海相碳酸盐岩层系油气多期成藏与保存机理;同时指出要加大碳酸盐岩地区的地震、钻井和测井等系列技术的攻关力度,以提高勘探的成功率。

Particularity of petroleum exploration on marine carbonate strata in China sedimentary basins

Marine carbonate strata,at least bearing 300×10~8 t petroleum,is very important exploration objective in China.Although some large carbonate oil-gas fields such as Tahe oilfield and Puguang gasfield have been found for last 50 years,the found petroleum reserves in carbonate strata is still small.This is due to low investment of exploration,but the main reason lies in the particularity of petroleum geology of marine carbonate layer in China,including the following 7 aspects:(1)carbonate strata are buried in multiple cyclic superimposed basins;(2)the depth to the carbonate strata is large and its age is old;(3)the source rocks are characterized by multiple lithology and multi-stage hydrocarbons generation;(4)types of reservoir rocks are diverse and the heterogeneities are strong;(5)types of trap are diverse and mainly subtle and compound;(6)the reservoirs were generally adjusted and destroyed and its condition of preservation is complex;(7) the distribution of reservoirs are complex and it is difficult to be predicted.In order to discover more petroleum in carbonate strata and to lighten the conflict of supply and demand of petroleum resources,research on theories of the laws of the petroleum distribution and exploration technologies in marine carbonate basin should be strengthened.On basis of petroleum geologic characteristics of carbonate strata,three theoretical problems to be solved of petroleum accumulation in Chinese marine carbonate basins are put forward as follows:(1) the developing environment and evolution of tectonics of marine carbonate strata and their control of effective source rocks;(2)hydrocarbon accumulation mechanism in the carbonate carrier beds;(3)mechanisms of multi-stage hydrocarbon accumulation and preservation.The paper also suggests that seismic method,drilling and well logging should be improved in exploration for petroleum in carbonate strata.