塔河油田海西早期岩溶水文地貌特征及其演化

Hydrogeomorphologic characterization and evolution of the Early Hercynian karstification in Tahe oilfield,the Tarim Basin

塔里木盆地塔河油田海西早期形成了复杂的碳酸盐岩岩溶缝洞系统,其发育规模在塔河油田东部主体区和西部外围区表现出显著的差异性。岩溶水作为岩溶发育的关键因素,在不同地质背景下表现出的水文学特征及水动力作用与岩溶缝洞系统的发育密切相关。为了深入认识和阐述东、西部岩溶储层发育机制,以现代岩溶理论为指导,基于高精度三维地震资料,利用地震属性提取技术及地震成像相关技术,对埋深5 000 m以下的古岩溶地貌和古水文网络进行了恢复。通过对东、西部水文地貌特征的精细描述,厘定了岩溶演化阶段。研究结果表明:1)东部主体区为岩溶高原区,以峰丛、溶丘等高幅差地貌为主,地表水强烈的垂向侵蚀作用形成了干谷、盲谷、伏流、峡谷、天生桥等地貌组合,同时,发育了完整的地表-地下双重水系网络。该水文地貌特征反映了东部主体区经历了一段长期稳定的岩溶作用阶段。2)西部外围区为岩溶盆地区,地形较为平缓,发育低幅度溶丘;地表水以侧向溶蚀、侵蚀为主,展现出蛇曲状网络结构,尚未形成连续的地下水系网络,说明西部外围区岩溶作用时间相对有限。综合区域构造演化史,认为塔河油田东部主体区岩溶发育阶段处于壮年期,西部外围区岩溶发育阶段处于青年期。

Complex karst fracture-vuggy systems formed during early Hercynian of Tahe Oilfield show greatly disparities in scales and distributions in the east （blocks of interests） and west （peripheral area） parts of the oilfield.Karst water was thought to be the key factor during the karstification under varying hydrogeomorphology and hydrokinetic conditions against different geological settings.To deeper understand and interpret the mechanisms behind the development of karst reservoirs in western China,the authors restored paleokarst geomorphology and hydrology networks buried in a depth less than 5000m with modern karst theories as guidance,and high-precision 3D seismic data,seismic attribute abstraction and seismic images,as basis.A fine description of hydrogeomorphology of the east and west parts of the oilfiled were also carried out to help define the evolution stages of the karstification.The results show that the east part was developed into karst plateau with high-relief peak clusters and karst mounds as the primary landform units.Typical landscape combinations consisting of dry valleys,blind valleys,swallet steams,canyons and natural bridges,were formed by strong vertical erosion from surface water.Integrated drainage systems made up of both surface and underground hydrologic networks were also formed there.These features reveal that the part had gone through a long and stable period of karstification.The results also point out that the west part is mostly a karst depression holding gentle topography gradient and karst mounds with relatively lower relief.The surface water network was observed to erode largely laterally into snaking networks in the part.However,continuous underground water networks failed to come into being,indicating a shorter period of karsitification in the part.Combining these observations with regional tectonic evolution data,the authors suggests that the karst re-servoirs in the east of the oilfield are still in their stage of maturity and those in the west are during their adolescence phase.