层序地层学在油田开发中的应用实践

总结了依据地层基准面原理进行开发调整阶段储层精细对比和油藏精细描述的方法。以湖泛面为层序界面,在濮城油田沙三中6-10油藏内识别出超短期、短期、中期和长期四级界面和基准面旋回,短期旋回是油藏细分开发调整的最小单元。短期基准面上升期,形成向上物性变差、高渗段位于砂层下部的层内非均质模式,而短期基准面下降期,形成向上物性变好、高渗段位于中上部的层内非均质模式。中长期基准面较低部位沟道较为发育,砂体厚度大、分布广、物性较好,而在中长期基准面较高部位沟道不发育,砂体厚度薄、面积小、储层物性较差。中长期基准面上升旋回内形成向上物性变差的层间非均质格局,而在中长期下降期则形成向上物性变好的非均质性格局。在水下扇前缘区,近湖心剖面砂体中的沟道成份较小,砂体连通性、连续性及物性较差,而向岸方向储层相对较连续,物性较好。基准面低位处的砂体油气储量和储量丰度均较高,而基准面高位处砂体油气储量和丰度较低。基准面低位处砂体物性较好,较易动用,采出油气数量和采出程度较高,但由于其本身的储量较大,剩余油仍占据着主要的地位。基准面高位处砂体物性较差,储量较难动用,采出油量和采出程度均较小,但受其本身储量的限制,剩余油量在剩余可采储量中的比例较小。

Application of Sequence Stratigraphy to Improving Mature Oil Field Recovery

Pucheng oil field is located in the Dongpu depress, Henan province. Four scales of sequence cycles are distinguished in study area, including very short term cycle, short term one, medium term one and long term cycle. The heterogeneities study indicates that base level controlled sand distribution and the reservoir heterogeneities. In the rising semi-cycle of short cycle , the property are better at the bottom of the sands and becoming poorer to top, while with a totally different way in the falling semi-cycle. At the lower position of medium and long term cycles, braided channel are well developed with a widespread area and good property, while at the high position of the cycles, the braided channel are small and the sand spread area are limited with poor property. In the rising semi-cycle of long-and medium-cycles, the reservoir become poorer from bottom to top, while it becomes better in the falling semi-cycle. From the bank to lacustrine center, the braided channel becomes weaker and smaller, and the reservoir architecture turns to be mainly of sheet-like sands near the front of middle fan from mainly of channel sands near the middle fan, and finally of lacustrine mud at the lake center. The distribution of OOIP(original oil in place) and the residual oil are also controlled by the baselevel framework. OOIP is high at the low baselevel place in the framework, and high while the baselevel is at the high place. Sandbody at the low baselevel place is always with good property and easy to be diploid, so it is often placed on the important place in the development, and with large output. But with high OOIP, its remaining amount is always in large quantities. Sandbody at the high baselevel is always with poor property and difficult to deploid, and be put in the secondary place in the development, so its output is little. But with low OOIP, its ratio of remaining oil in the reservoir is not important.