柴达木盆地一里坪坳陷新生界咸化特征及生烃潜力分析

An analysis of Cenozoic hydrocarbon generation potential and salty characteristics of Yiliping depression in Qaidam basin

柴达木盆地目前所发现的油气都围绕着侏罗系、古近—新近系及第四系富烃洼陷区分布。近年来,围绕"富烃洼陷"油气勘探,发现了昆北和英东两个"亿吨级"油田、阿尔金山前东段"千亿方"天然气及扎哈泉"亿吨级"致密油勘探区,勘探成效显著。随着柴达木盆地建设千万吨高原油气田及新区、新领域勘探的迫切需求,借助于中国石油重大科技专项,利用硼元素及黏土矿物资料,引用科奇公式开展古水体盐度恢复,明确柴达木盆地新生界为咸化湖盆沉积。从柴达木盆地新生界咸化特征及与已知富烃洼陷进行类比,结合一里坪坳陷周缘有机地球化学测试资料,提出一里坪坳陷为潜在的生烃洼陷,可能为新的富烃洼陷,围绕该洼陷进行油气勘探将是一个新的接替领域,对柴达木盆地油气勘探具有重大战略意义。

So far, both oil and gas found in Qaidam Basin are distributed around the Jurassic, Tertiary and Quaternary hydrocarbonrichsub-sag areas. In recent years, surrounding hydrocarbon-rich depression in petroleum exploration, Kunbei and Yingdong, thetwo＂hundred million tons grade＂oilfields,＂hundred billion cubic meters＂gas in the eastern front part of Altun Mountain and＂hundred million tons grade＂tight oil in Zhahaquan exploration area have been discovered, and the exploration has made greatsuccess. Along with the construction of ten million tons of plateau oil and gas fields in Qaidam Basin and the urgent need of finding new fields and new exploration areas and with the aid of major science and technology projects of Petro China, the authors used thedata of boron element and clay minerals and employed Couch formula to carry out paleosalinity recovery, and finally confirmed thatthe Cenozoic sediment is salty lake deposition in Qaidam Basin. Comparing the Cenozoic salty characteristics of Qaidam basin withthose of known hydrocarbon-rich depression in combination with organic geochemical test data of Yiliping depression, the authorshold that Yiliping depression is a potential hydrocarbon generation depression and is probably a new hydrocarbon-rich one. The oiland gas exploration surrounding the depression will be a new successive field and should have important strategic significance in oiland gas exploration in Qaidam Basin.