连续型油气藏形成条件与分布特征

The formation conditions and distribution characteristics of continuous petroleum accumulations

随着油气藏勘探的不断深入,岩性油气藏勘探从有明显圈闭型的油气藏,进入大规模连片储集体系的连续型油气藏;地层油气藏从东部盆底基岩潜山油气藏,进入中西部大型不整合面控制的大规模地层油气藏。根据圈闭是否具有明确界限和油气聚集分布状态,把油气藏分为常规圈闭型油气藏和非圈闭连续型油气藏两大类,明确了连续型油气藏内涵,阐述了其主要地质特征。大型浅水三角洲体系及其砂质碎屑流砂体是连续型油气藏形成和大面积分布的地质基础,成岩相定量评价是低—特低孔渗连续型储层评价的重要方法。在湖盆中心陆相沉积上,建立了以鄂尔多斯盆地长6组为代表的湖盆中心深水砂质碎屑流重力成因沉积模式,拓展了中国湖盆中心部位找油新领域;在储层评价上,以四川盆地须家河组为例,系统提出了成岩相内涵、分类和评价方法,运用视压实率、视胶结率和视溶蚀率等参数定量表征成岩相,为落实有利储集体分布提供了理论依据和工业化评价方法。中国连续型油气藏储量规模与潜力很大。

Accompanied by the great development of hydrocarbon exploration, lithologic accumulation exploration areas have changed from the reservoirs with clear traps into the continuous petroleum accumulations with geographically extensive reservoirs,while stratigraphic accumulation exploration areas have turned from the eastern pelvic floor bedrock buried hill hydrocarbon accumulations into the Midwest large unconformity-controlled large-scale stratigraphic reservoirs. Depending on whether the traps have clear boundaries and distribution of oil and gas accumulations, reservoirs are divided into trap-type and non-trap ＂continuous-type＂ . The major characteristics of continuous petroleum accumulations include lack of obvious trap boundaries, low or ultra-low porosity and permeability, in-source or near-source distribution, limited role of buoyancy in hydrocarbon accumulation, mainly non-Darcy flow, no migration or mainly primary migration, abnormal pressure, complex distribution of oil, gas and water, etc. Continental sedimentary sand bodies in the shallow-water delta depositional system and its sandy debris flow are geological foundations for continuous petroleum accumulations. Quantitative assessment on diagentic facies is an important way to evaluate the low or ultra-low porosity and permeability continuous reservoirs. Deep-water ＂sandy debris flow ＂ gravity-cause depositional model in basin centers represented by Chang 6 Formation in Ordos Basin expands new fields for oil exploration in the basin centers of China. The concepts, classification, and evaluation methods of diagenetic facies represented by Xujiahe Formation in Sichuan Basin are systematically proposed using the rate of compaction, cementation and dissolution, providing the reference and industrialization evaluation methods for the favorable reservoir evaluation. The continuous petroleum accumulations have great exploration potential in China.