东海盆地主要地质特点及找气方向

包括东海盆地在内的中国东部大陆边缘盆地具有“内张外挤”的双带构造性质 ,裂陷内带不断由陆向洋扩张离散 ,从而形成了 2个不同时代的裂陷带 ,即晚白垩世—古新世裂陷带和始新世裂陷带。西湖凹陷是位于始新世裂陷带内的继承性凹陷 ,具有优越的生烃条件和一批大、中型构造 ,具备形成大气田的条件 ,但由于缺乏良好的区域性盖层 ,以及晚期断层强烈活动造成油气散失 ,限制了大气田的形成 ,其勘探工作应以寻找富集断块为重点 ,要“着眼构造、着手断块、探索岩性”。丽水凹陷是位于晚白垩世—古新世裂陷带内的间断型凹陷 ,其含气前景存在两大风险 ,即大规模的削蚀破坏和CO2 的存在 ;灵峰潜山披覆构造带和东次凹西坡的潜山超覆带是该凹陷优先勘探的地区

MAIN GEOLOGICAL CHARACTERISTICS AND GAS EXPLORATION DIRECTIONS IN EAST CHINA SEA BASIN

The continental margin along the eastern China, including East China Sea basin, is characterized by a double_belt tectonics of extensional inner and compressive outer. The extensional inner has a continuous opening and divergence towards the ocean, resulting in two rift zones with different ages, i.e. Late Cretaceous_Paleocene zone and Eocene zone. As an inherited sag within the Eocene rift zone, Xihu sag has remarkable conditions to generate hydrocarbon and a great number of large and medium structures, showing a likehood of forming large gasfields. However, giant gas accumulations are unlikely to form in the sag, due to lack of effective regional seals and hydrocarbon loss caused by late intensive fault activities. Thus gas exploration in Xihu sag should focus on searching for gas_rich faulted blocks, and take an approach to 'aiming at structures, starting with faulted blocks and probing into lithology'. For Lishui sag, an intermittent sag within the Late Cretaceous_Paleocene rift zone, there are two risk factors of gas accumulation, i.e. wide erosional truncation and presence of carbon dioxide, but Lingfeng drape structure zone and the overlapped buried?hill zone on the west slope of the eastern sub_sag may be considered as the preferential exploration areas.