面积深度法在库车坳陷北部盐下构造变形研究中的应用

塔里木盆地库车坳陷北部油气资源丰富,但由于受研究区地表和地下构造双重复杂特征及巨厚膏盐层的影响,其深层地震资料的成像质量与精度不理想,准确研究盐下构造形态存在较大难度。为此,基于前人的研究成果,根据最新的三维叠前深度偏移地震剖面,建立了克拉苏构造带盐下构造层的初始构造模型,并运用面积深度法分析了盐下构造层的变形特征和变形机制。结果表明:①盐下层构造的分布以克拉苏断裂为界线,断裂以北主要发育基底卷入的高角度逆冲构造,而断裂以南则主要发育滑脱构造;②克拉苏断裂以南区域滑脱面的位置介于8.01~10.23 km深度,推测该滑脱层为三叠系与下伏基底之间的不整合面;③博孜区域的滑脱距离为7.49 km,大北区域的滑脱距离为14.35 km,克深5区域的滑脱距离为12.46 km,克深1-2区域的滑脱距离则为1 6.32 km,该区盐下构造层的滑脱距离呈现出自西向东逐渐增加的趋势,表明从西向东构造变形越来越强烈。

Application of area-depth method in studies on the deformation of subsalt structures in the northern Kuqa Depression

The northern Kuqa Depression in the Tarim Basin contains rich hydrocarbon resources. However, due to the complicated features in surface and subsurface structures within the area, together with negative impacts of gypsum rocks with significant thicknesses, seismic data for deeper formations failed to generate satisfactory images. Consequently, significant challenges were encountered in the determination of subsalt structures. Based on the previous studies, the latest 3D pre-stack depth migration (PSDM) seismic profiles were used to construct the initial structural model for subsalt structures in the Kelasu Structural Belt. In addition, the area-depth method was deployed to analyze the features and mechanism of deformation in subsalt structural layers. The following research results were achieved. (1) Subsalt structures distribute with the Kelasu Fault as the boundary. The north of the Fault is dominated by high-angle thrust structures with the involvement of basement, whereas the south is dominated by detachment structures. (2) With detachment surfaces in the south of the Kelasu Fault distributed between 8.01 km and 10.23 km in depth, the layer was presumed to be the unconformity surface between the Triassic and the underlying basement. (3) With detachment displacements of 7.49 km in the Boze area, 14.35 km in the Dabei area, 12.46 km in the Keshen-5 area and 16.32 km in the Keshen 1-2 area, the displacements of subsalt structures in the areas increase from west to east. The trend may reflect the ever-increasing deformation intensities of structures from west to east. Relevant research results may provide reliable foundation for hydrocarbon exploration within the concerned area.