特低渗—致密砂岩储层成藏模拟试验与成藏机理

Simulation Experiment of Petroleum Migration and Accumulation Mechanism for Extra-low Permeability and Tight Sandstone Reservoirs

对采自鄂尔多斯盆地延长组的8块渗透率为（0.050-2.812）×10-3 μm2的特低渗—致密砂岩岩芯样品进行石油驱替成藏模拟试验。试验采用驱动压力分段逐级提升式连续油相充注。结果表明：特低渗—致密砂岩储层石油运移、聚集、成藏机理与常规储层明显不同。随着石油不断注入和驱动压力的不断增高,岩芯中孔隙水逐渐排出,含油饱和度随之增高,并且增高趋势呈现先快后慢的指数式特征;样品最终含油饱和度与渗透率相关关系不显著,与孔隙度呈正相关;特低渗—致密储层具有原油活塞式驱替运移的成藏机理,成藏效率高,石油成藏富集受到油源规模、驱动压力、成藏流体性质等因素的影响;优质烃源岩是特低渗—致密储层石油富集的主控因素。

Petroleum displacement reservoir was simulated with 8 extra-low permeability and tight sandstone core samples （the permeabilities were （0. 050-2. 812） × 10.3 μm2） from Yanchang Formation of Ordos Basin. Oil continuous charging with piecewise and constant pressure was used in the experiment. The results show that the mechanism of petroleum migration and accumulation of extra-low permeability and tight sandstone reservoir is totally different from conventional reservoir; with the increase of displacement pressure and oil continuous injection, pore water of core is gradually discharged, and oil saturation increases accordingly with an exponential feature that the increasing trend of oil saturation is slow after the first fast; the relationship between final oil saturation of sample and permeability is not significant, while the final oil saturation is positively correlated with porosity; the accumulation mechanism of extra-low permeability and tight sandstone reservoir is crude oil displacement migration with piston style, accumulation efficiency is high, and the petroleum accumulation and enrichment are influenced by the scale of oil source, displacement pressure, accumulation fluid property, and so on; high-quality source rock is the main controlling factor of petroleum accumulation andenrichment in extra-low permeability and tight sandstone reservoirs.