东营凹陷北部陡坡带深层砂砾岩扇体成岩圈闭有效性评价

Evaluation on trap effectiveness for deep fan diagenetic trap in the northern steep slope zone of Dongying sag

东营凹陷北部陡坡带深层砂砾岩扇体发育扇根封堵的成岩圈闭岩性油藏,圈闭的形成受不同沉积相带沉积组构与成岩作用差异的影响,而圈闭有效性评价是预测圈闭含油气性的关键。为了有效预测成岩圈闭的含油气性,从扇根地质特征和油藏特征分析入手,剖析研究区扇根封闭机制和圈闭评价原则,在此基础上,利用不同勘探阶段的相关资料,建立适用的圈闭有效性评价方法。研究结果表明:扇根亚相泥质杂基含量高、压实与杂基重结晶作用强烈,纵向上叠置的扇根可作为侧向封堵层和局部盖层;成岩圈闭的主要封闭机制是物性封闭,扇根与扇中之间的突破压力差决定了封堵油气的高度;利用全直径取心油驱水实验数据对压汞实验测定的汞驱气突破压力进行校正,并分别利用核磁共振测井和常规物性资料建立油驱水突破半径的计算方法,进而求得油藏条件下油驱水的突破压力差,对圈闭的有效性进行评价。应用结果表明,建立的圈闭有效性评价方法合理、可行,可有效指导勘探部署。

The deep fan diagenetic trap developed widely in the northern steep slope zone of the Dongying sag and the differences in sedimentary fabric and diagenesis play important role in the reservoir forming. How to evaluate the trap effectiveness is the key to exploration. By analyzing geological characteristics of root-fan and oil reservoir,the object of trap evaluation,the root-fan sealing mechanism and evaluation principle were determined to predict oil-bearing properties of diagenesis trap effectively. Based on this,according to different data at different exploration stages,the trap effectiveness evaluation methods suitable for different exploration stages were established. The results show that the root-fan developed high clay heterobase and strong compaction and heterobase recrystallization so the root-fan could be a lateral sealing seal or a local seal. The main seal mechanism of diagenetic trap was capillary sealing,the difference of displacement pressure between root-fan and mid-fan determined oil column height. Mercury injection data should be corrected by experimental data of oil displacing water in whole diameter core,and the method of calculating breakthrough radius of oil displacing water using NMR data or routine physical data were established,by which the breakthrough pressure difference under oil reservoir condition can be obtained to evaluate the trap effectiveness. The analysis of the applied result shows that this evaluation method can be used to guide exploration.