轮南低凸起气洗作用响应及定量评价  

Quantitative Evaluation and the Geochemical Responses of Gas Washing in Lunnan Petroleum Province

作　　者：吴楠[1,2] 蔡忠贤[1,2] 杨海军[3] 陈建渝[1,2] 刘显凤[1,2] 顾乔元[3] 

机构地区：[1]中国地质大学资源学院,湖北武汉430047 [2]湖北省油气勘探开发理论与技术实验室,湖北武汉430074 [3]中国石油塔里木油田分公司勘探开发研究院,新疆库尔勒841000

出　　处：《地球科学（中国地质大学学报）》2009年第3期486-492,共7页Earth Science-Journal of China University of Geosciences

基　　金：国家重点基础研究973计划“中国海相碳酸盐岩层系油气输导体系与运聚机理”项目(No.2005CB422105)

摘　　要：自喜山期,过量干气自东向西对轮南低凸起原始油藏的大规模侵入、冲刷,诱发本区持续性气洗分馏作用的发生.在各组分气液溶解平衡的格架下,气洗作用将导致残余油中正构烷烃的大量损失以及次生凝析气藏的形成.地球化学研究表明,残余油与凝析油中轻烃组分(C6-C8)的变化趋势具有典型的气洗分馏特征.同时,基于气洗作用模型,通过对各层系原油正构烷烃相对蒸发量(Q)的计算,定量描述了轮南地区气洗作用的强度.计算结果显示,奥陶系的油气藏曾遭受强烈的气洗作用,原油中正构烷烃的相对蒸发量由东向西表现出依次递减的特征.其中,轮古东地区Q值高达97%;位于轮南低凸起中部的轮古2井以及轮古18井地区,正构烷烃相对蒸发量较小(Q=20%～76%);而在更加靠近西部的轮古17及轮古100井,其原油中正构烷烃分布正常(Q=0),并未发生气洗分馏作用.另一方面,石炭系以及三叠系的油气藏均表现出未遭受气洗作用的特征,证实了喜山期大量干气的优势运移通道被限制于海西早期运动所形成的奥陶系岩溶缝洞体系中的事实.因此,奥陶系,尤其是位于临近气源区的轮古东地区,是轮南地区气藏的有利靶区.Lunnan hydrocarbon province has recently experienced intensive gas invasion since the Himalayan movement, and some of the oils in the Ordovician reservoir show characteristics of progressive fractionation by gas moving. Based on the frame-work of the components phase equilibrium, the process of gas washing can deplete the n alkanes of the oil and produce the subsequent condensates. Geochemistry analysis shows that both the residual oil and the condensates indicate the phase fractionation characteristics on their light ends （C6-C8）. Moreover, gas chromatogram data show that the altered oils are depleted of light n-alkanes. Through calculating the mass depletion of oil in n-alkanes relative to an unfractionated oil （Q）, it determines that oils in the Ordovician reservoir experienced great alternation of gas washing, and the Q value decreases westward. However, oils in the Carboniferous and Triassic reservoir show no depletion of the n-alkanes.

关 键 词：气洗作用 正构烷烃相对蒸发量 轮南低凸起 蒸发分馏作用 定量化 

分 类 号：P618[天文地球—矿床学]