鄂尔多斯盆地怀远运动期岩溶古地貌恢复及油气地质意义  

The restoration of palaeokarst geomorphology during Huaiyuan Movement and its petroleum geological significance in Ordos Basin

作　　者：吴淳 刘波[1] 魏柳斌[2] 刘新社[2] 芦飞凡 石开波[1] Wu Chun;Liu Bo;Wei Liubin;Liu Xinshe;Lu Feifan;Shi Kaibo(School of Earth and Space Sciences,Peking University,Beijing 100871;Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi'an 710018)

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]中国石油长庆油田分公司勘探开发研究院,西安710018

出　　处：《地质科学》2024年第3期732-743,共12页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：中国石油长庆油田公司重大科技专项“鄂尔多斯盆地中元古界-奥陶系构造沉积演化、成源机制与勘探新领域研究”(编号:ZDZX2021)资助。

摘　　要：怀远运动不整合面附近是鄂尔多斯盆地寒武系的勘探新方向。在地层的暴露剥蚀和大气淡水的淋滤溶蚀作用下,寒武系顶部发育了风化壳岩溶储层,但岩溶古地貌尚未得到恢复,难以满足勘探的要求。本文基于录井、测井、岩心及野外剖面等资料,通过地层划分、对比和等时地层格架的建立,在寒武系上覆地层中优选马三段顶面作为岩溶古地貌恢复的基准面。根据寒武系顶部与马三段顶面之间的印模厚度,绘制地层等值线图,并恢复岩溶古地貌。基于此,可以划分出岩溶高地、岩溶斜坡和岩溶盆地共3个古地貌单元,在岩溶斜坡中可划分出次一级地貌单元——残丘。研究区在怀远运动期为西高东低的地貌格局,西部庆阳、同心、鄂尔多斯一带为岩溶高地,中部条带状岩溶斜坡区发育乌审旗、大荔等残丘地貌,东部吕梁一带为岩溶盆地。根据古地貌单元与储层发育的关系,岩溶高地和岩溶斜坡内的残丘有利于储层的形成,是天然气勘探的有利方向。The unconformity of Huaiyuan Movement is a new exploration direction of Cambrian in Ordos Basin.The weathering crust karst reservoir developed at the top of the Cambrian under the exposure and leaching of meteoric water,but the paleokarst geomorphology has not been restored and it is difficult to meet the requirements of exploration.Based on the data logging,cores and field section,this work selects the top of Ma-3 member as the base level of palaeokarst geomorphology restoration in the overlying strata of Cambrian by stratigraphic classification,correlation and establishment of isochronous stratigraphic framework.According to the strata thickness of impression between the top of Cambrian and the top of Ma-3 member,the contour map of strata is drawn and the palaeokarst geomorphology is restored.Based on this,three paleogeomorphic units can be divided:karst highland,karst slope and karst basin,and the secondary geomorphic unit-monadnock can be divided into karst slope.During the Huaiyuan Movement,the study area was high in the west and low in the east topographically.The Qingyang,Tongxin and Erdos areas in the west were karst highlands,the Wushenqi and Dali monadnocks developed in the central belted karst slope,and Lüliang area in the east was karst basin.According to the relationship between palaeokarst geomorphic units and karst reservoirs,karst highlands and monadnocks in karst slopes are conducive to the formation of reservoirs and are favorable directions for natural gas exploration.

关 键 词：古地貌恢复 怀远运动 风化壳岩溶 岩溶储层 鄂尔多斯盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]