提高煤系页岩储层TOC计算精度的改进方法

A method to improve the accuracy of TOC calculation for coal- measure shale reservoirs

1.长江大学地球物理与石油资源学院,湖北武汉 430100;
2.长江大学油气资源与勘探技术教育部重点实验室,湖北武汉 430100;
3.中国科学院深海科学与工程研究所,海南三亚 572000;
4.中国石油川庆钻探工程有限公司苏里格项目经理部,四川成都 610051

1. College of Geophysics and Petroleum Resources,Yangtze University,Wuhan 430100,China;
2. Key Laboratory of Oil and Gas Resources and Exploration Technology,Ministry of Education,Yangtze University,Wuhan 430100,China;
3. Institute of Deep-sea Science and Engineering,Chinese Academy of Sciences,Sanya 572000,China;
4. Sulige Project Management Department of Chuanqing Drilling Engineering Company Limited,CNPC,Chengdu 610051,China

总有机碳含量(TOC)是决定烃源岩质量的最重要参数。为了准确评价煤系页岩气储层的TOC参数,以四川盆地Q区龙潭组C1井海陆过渡相页岩气储层为例,对提高储层TOC参数计算精度的方法进行了研究。根据研究区的地质特点,结合自然伽马能谱测井数据,对原始Δlog R方法进行改进,形成了基于自然伽马能谱测井的双Δlog R方法。首先,将岩心TOC数据按岩性分为煤层和非煤层,然后,将自然伽马能谱测井数据(钍钾比(Th/K)和钍铀比(Th/U))分别与煤层TOC和非煤层TOC进行相关性分析,各自选择最高相关性的数据与Δlog R拟合,计算煤层和非煤层的TOC。结果表明,基于自然伽马能谱测井的双Δlog R方法和传统方法相比,C1井煤层和非煤层TOC计算相关性最高可以提高到0.78和0.85,煤层和非煤层TOC的绝对误差最低都可以降到0.01%,煤层和非煤层TOC的相对误差降低到14.93%和12.53%。将基于自然伽马能谱测井的双Δlog R方法应用于四川盆地S区Y组C2井,取得了较好的效果。改进的方法适用于研究区页岩气储层黏土含量高,非均质性强,且存在黑色煤层的页岩储层,有效弥补TOC与铀(U)含量无明显相关性的不足,具有较好的适用性和推广性,可以有效辅助研究区页岩气储层的勘探开发。

Total organic carbon (TOC) content is the most important parameter in determining the quality of source rocks.In a case study of a transitional shale gas reservoir in the Longtan Formation at Well C1 in area Q,the Sichuan Basin,our efforts focus on how to improve TOC calculation for coal-measure shale gas reservoirs.Based on the geological characteristics of the study area and natural gamma ray spectral log data,the Δlog R method is modified to formulate a dual Δlog R method based on natural gamma ray spectroscopy logging.The reservoir is lithologically divided into two types:coal seam and non-coal seam,according to core TOC data.Th/K and Th/U correlations with TOC contents in coal seams and non-coal seams are analyzed to select the data with the highest correlations for TOC calculation using Δlog R at coal seams and non-coal seams.The results show improved correlations up to 0.78 and 0.85,decreased absolute errors to 0.01% and 0.01%,and decreased relative errors to 14.93% and 12.53% for TOC calculation at coal seams and non-coal seams,Well C1,respectively compared with the traditional method.The dual Δlog R method based on natural gamma ray spectroscopy logging is also successfully applied to the Y Formation at Well C2 in area S,the Sichuan Basin.The improved method is feasible in the context of high clay content,strong heterogeneity,and black coal seams in the study area;the problem of the low correlation between TOC content and U content could also be solved.This method could be applied to similar prospects and offer technical support to shale gas exploration and production.

油气资源与勘探技术教育部重点实验室(长江大学)开放基金资助项目(K2021-08)资助。

10.12431/issn.1000-1441.2024.63.04.010