鄂尔多斯盆地延长组储层致密化及其影响下的致密油充注特征

通过对鄂尔多斯盆地延长组储层成岩作用、致密历史、油水分布特征的分析，并结合充注动力与阻力的计算，探讨了储层早期致密化影响下的致密油充注特征。结果表明，延长组长6-长8段储层孔隙演化经过4个阶段，在中成岩阶段A1期基本达到致密，而此时油气大规模充注尚未开始。储层早期致密化形成的高充注阻力导致浮力难以成为驱替致密油运移的有效动力。同时，结合该区具有紧邻源岩的致密砂岩普遍含油、"甜点"富油且流体分异性差的特征，认为广泛发育的长7段烃源岩与长6和长8段储层间的剩余压力差是致密油充注的主要动力，且是导致致密砂岩含油而甜点富油的重要因素。

Reservoir densification and tight-oil charging in Yanchang Formation,Ordos Basin

The Yanchang Formation in Longdong area, Ordos Basin, is characterized by low porosity and permeability and is considered as a tight-oil reservoir. However, reservoir densification and its influence on oil charging are not well-understood. Based on the analysis of reservoir diagenesis, densification history, oil-water distribution, driving force and resistance, the oil charging process in tight-sand reservoirs was discussed. The results showed that porosity evolution of the Chang 6-Chang 8 reservoirs has gone through four stages, and they became tight during the diagenetic A₁ stage, which was prior to oil charging. And the large resistance due to narrow pore throats made it impossible for buoyancy to be a driving force. Since the tight-sand reservoir is currently oil-saturated with "sweet spots" in locally high-quality reservoir, the excess pressure difference between the Chang 7 source rock and the Chang 6-Chang 8 reservoir is considered to be the main driving force for oil charging in the tight reservoirs.