厚层辫状河道期次厘定与多期砂体叠置规律

Stacked rule and stage-time division for thick-layer, multi-period braided river sandbodies

厚层复合辫状河道砂体由于叠置切叠程度较深,两期叠置的河道砂体间无明显岩电响应特征,给砂体期次厘定带来较大难度,从而影响单期河道平面组合与砂体平面追踪对比的准确性。为对完全复合在一起的厚层河道砂体进行分期,利用测录井等资料,在标志层拉平基础上,通过"去压实效应邻井单期河道标定法",完成复合河道砂体的分期,然后,如果具备连续取芯资料,可辅助验证分期结果的可靠性。在单井垂向分期基础上,采用"单期砂厚中心连线法",结合基于连井剖面的单一河道识别结果,完成单期河道平面延伸轨迹的追踪和对比。结合野外露头、现代卫片和经典地质概念模式,将多个单期河道按发育先后有规律叠置在一起,总结其沉积与演化规律,最终完成复合辫状河道沉积过程与历史重建。厚层辫状河道砂体期次厘定与平面单期河道砂体分布规律研究,有助于揭示砂体空间富集规律,进而提高砂体钻遇率。

The thick braided river sandbodies whose incised degree was deeper, so it was no obvious mark between electrical response characteristics between two stages channel sandbodies, determined to the stage-time division difficultly, further, the accuracy of single stage channels combination and tracking comparison in the plane were affected. In order to conduct identification and classification for fully complex channels, the “relaxation rebound techniques” based on removal compaction effects were adopted to finish the stage-time division complex river stage by logging, detection logging datum and so on. Then, the reliability of the results was used to test and verify the continuous coring data. On the basis of vertical stage-time division of single well, the tracking and comparison were done by using “the sand thickness center line connecting method” based on modern sedimentary and geological models and theories, and the multiple single period channels were regularly stacked together to summarize the rule of sedimentary evolution. At last, the deposition process and historical reconstruction of complex braided channels were finished. The research results can help to reveal the rule of stacked sands and improve the rate of sand drilling.