189 / 2019-06-11 21:31:32

地震地貌学在碳酸盐岩中的应用——以四川盆地高磨地区寒武系龙王庙组为例（Carbonate Seismic geomorphology: A case study of Cambrian Longwangmiao Formation, Gaoshiti-Moxi area, Sichuan Basin, China）

地震地貌学；四川盆地；寒武系龙王庙组；沉积期古地貌；地震正演；颗粒滩；岩溶型储层 Seismic geomorphology, Sichuan Basin, Cambrian Longwangmiao Formation, Sedimentary paleogeomorphology, Seismic forward modeling, Shoal, Karst reservoir

地震资料是对古老地层沉积界面及沉积过程的综合反映，本次研究结合三维地震及大量实钻井资料，应用地震地貌学对川中地区寒武系龙王庙组沉积期古地貌进行分析恢复。本文充分考虑地层沉积充填特征、构造背景、沉积速率等因素，对比印模法和残厚法恢复原理，认为沧浪铺组上部泥质岩厚度能较好的反映龙王庙组沉积期古地貌；结合地震正演模拟，筛选出对沧浪铺组上部泥质岩层“敏感”的地震物理属性对龙王庙组沉积期古地貌进行重建。研究表明龙王庙组底界波谷振幅值越大，则沉积期地貌相对越高；加里东古隆起在龙王庙沉积期已初具雏形，整体呈现出北西高、南东低，中部北东—南西走向地貌低地将研究区分隔为磨溪地貌高带和高石梯地貌次高带，呈“两隆一凹”的古地貌格局。地貌展布控制了颗粒滩和储层发育，地貌高地不仅颗粒滩面积广厚度大，且更易遭受同生—准同生暴露影响，为后期顺层岩溶提供优势渗流通道，储层受岩溶改造更加强烈。志留纪磨溪主体地区龙王庙组抬升暴露，成为表生岩溶及顺层岩溶发育的优势区，因此，磨溪主体地区储层质量最好，其次为高石梯地区，而沉积地貌低地颗粒滩及储层发育欠佳。
Seismic data can comprehensively reflect the sedimentary interface and sedimentary processes of ancient strata. Based on 3D seismic data and a large number of actual drilling data, this study applied seismic geomorphology to analyze and reconstruct the sedimentary paleogeomorphology of the Cambrian Longwangmiao Formation in the central Sichuan Basin. In this paper, taking the sedimentary characteristics, tectonic setting and deposition rate into account and comparing methods of cast and isopach, it is believed that the thickness of the upper mudstone of the Canglangpu Formation can accurately reflect the sedimentary paleogeomorphology of the Longwangmiao Formation. Combined with the seismic forward modeling, the sensitive seismic physical attribute of the upper mudstone layer of the Canglangpu Formation was selected to reconstruct the sedimentary paleogeomorphology of the Longwangmiao Formation. The study shows that the larger the amplitude of the bottom boundary trough of the Longwangmiao Formation, the higher the paleogeomorphology during the sedimentary period; and that the Caledonian paleo-uplift has begun to take shape in the sedimentary period of the Longwangmiao, presenting high in the northwest and low in the southeast. And the central northeast-southwestern geomorphic lowland divided the study area into Moxi landform high belt and Gaoshiti landform subhigh belt. The paleogeomorphology controls the development of shoals and reservoirs, showing that the highland paleogeomorphology not only has a wide area of shoals, but also is more susceptible to the penecontemporaneous exposure, providing a superior porous channel for the later bedding karst which strongly modified the reservoir. The Longwangmiao Formation in Moxi area was uplifted and exposed during Silurian, and became the dominant area for epigenetic karst and bedding karst development. Therefore, the quality of the reservoir in Moxi area is the best, followed by the Gaoshiti area, while shoals and reservoirs are poorly developed in lowland.