Evaluation of Deep Carbonate Source Rocks with Low TOC and Contribution to Oil-Gas Accumulation in Tazhong Area,Tarim Basin
Huo Zhipeng
Jiang Tao
Pang Xiongqi
Wang Wenyang
Chen Junqing
Song Jianyang
Shen Weibing
Pan Zhihong
Abstract：As oil and gas exploration is conducted in deep and super-deep layers,effectiveness and contribution to oil-gas accumulation of carbonate rocks with high thermal evolution and low organic matter abundance (TOC≤0.5%)in deep layer need to be reevaluated. This is a key scientific issue for oil and gas exploration in carbonate rocks in China.Taking Tazhong area as an example,a qualitative discriminating criterion for carbonate source rocks was established by determining the lower limit of TOC,analyzing logging response and influencing factors of organic matter abundance.Geochemical and geological characteristics of carbonate source rocks with low TOC (CSRLTOC)in Tazhong area were studied,and their contribution to oil-gas accumulation was evaluated by numerical simulation and hydrocarbon generation potential.Results show that the lower limit of TOC for effective carbonate source rocks with immature, mature,high mature and over mature stages are TOC=0.50%,TOC=0.30%,TOC=0.20%and TOC=0.15%,respectively.The log responses of carbonate source rocks have some differences from those for mudstone.The relationship of TOC,natural gamma, acoustic slowness and elastic parameter are better.The organic matter abundance is influenced by sedimentary environment,color of rock,and lithology.Based on above results,the discriminating criterion was established.In the Tazhong area,the CSRLTOC is less than none source rocks,with 24-500 m,accounting for 37%of the total thickness.The thickness of CSRLTOC is 1.54 to 5.92 times of those source rocks with high TOC (TOC>5%).On the basis of the amounts of hydrocarbon expulsion,the amounts of effective hy-drocarbon expulsion,the amounts of hydrocarbon accumulation and the amounts of oil-gas resources,the contributions of the CSRL-TOC to oil-gas accumulation are 32.6%,27.4%,30.7%and 29.6%,respectively.Therefore,CSRLTOC should not be neglected in the theoretical research and resource evaluation.
Keywords：carbonate source rock with low TOCeffective source rockdiscriminating criterionevaluation of source rockcontribution to oil-gas accumulationdeep layerTazhong areapetroleum grology
Publication Date：2016-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：15( 2061-2074,2087 )