鄂北HJQ地区微幅岩溶古地貌恢复技术及实践

鄂尔多斯盆地北部HJQ地区地层接触关系不稳定, 马四段目的层构造幅度低, 残余厚度变化小, 且受煤层影响地震分辨率不足, 故现有标志层难以满足古地貌恢复精度的要求。采用基于连续小波变换的地震频谱延拓技术(FSE), 大幅提高了地震资料信噪比和分辨率, 井震对比标定证明了地震资料具有较高的保真度。利用高分辨率地震资料拾取了更为精确的目的层顶、底界面, 降低了上覆煤层干扰, 使得岩溶地貌的地质细节更丰富自然; 在测井-地震联合分析的基础上, 将山西组一段底部一套稳定的煤层-泥岩组合标志层作为新的印模基准面, 恢复的前石炭纪古地貌微幅特征清楚, 精度得到大幅提高, 实际钻井充填特征及测试产能的快速变化现象与恢复的地貌单元具有良好对应关系, 证明古地貌斜坡的残丘及沟谷周边为岩溶缝洞有利储层发育区, 洼地及沟谷中心部位泥质充填程度高, 为下一步滚动勘探指明了方向。

Carbonate reservoirs developed during the Ordovician Ma 4 Formation in the HJQ area of the northern Ordos Basin generated beneficial conditions for hydrocarbon accumulation.High-precision paleogeomorphic restorations have been proven to effectively identify reservoir locations.However, under the influence of unstable stratigraphic contact, low variations in residual thickness, interference of the coal seam, and insufficient seismic resolution, the existing marked stratum is insufficient for precise paleogeomorphological restoration.In this study, the application of seismic spectrum continuation technology based on the continuous wavelet transform significantly improved the signal-to-noise ratio and resolution and simultaneously premised high fidelity.With sufficient quality control analysis, the boundary of the target layer can be carved more accurately, and valid information concealed by the overlying coal seam can be observed.Hence, geological details of karst landforms are more abundant.The analysis of the joint logging-seismic data defines a set of stable combinations of the coal seam and mudstone located at the bottom of the Shanxi Formation as the datum to rebuild the pre-Carboniferous micro-paleogromorphic restoration.The results support a good correspondence between the different restored micro-paleogeomorphic units and the rapid changes in the filling characteristics and test productivity from actual drilling.This study confirmed that the reservoir zones of karst fractures and caves are concentrated around the residual hills and gullies of the paleogeomorphic slopes.Moreover, the degree of mud filling was high in the center of the depression and gullies.This improved understanding provides a direction for future rolling explorations.