The current study tested the gas component and carbon isotopic composition of gas samples from 6 oilgas fields at the northern margin of Qaidam Basin, and established a chart to quantitatively identify the mixing rati...The current study tested the gas component and carbon isotopic composition of gas samples from 6 oilgas fields at the northern margin of Qaidam Basin, and established a chart to quantitatively identify the mixing ratio of source-mixed gas. Besides, this research quantitatively investigated the natural gas generated by different types of organic matter. The results show that different ratios of source-mixed gas exist in the 6 oil-gas fields at the northern margin of Qaidam Basin. Among them, Mabei has the highest mixing ratio of coal-type gas, followed by Nanbaxian, Mahai, Lenghu-4, Lenghu-3 and Lenghu-5, with the ratios of coal-type gas 91%, 87%, 83%, 66%, 55% and 36%, respectively. Lenghu-3 and Lenghu-4 oil-gas fields were mainly filled by coal-type gas earlier. For Lenghu-3, the gas was mainly generated from low matured source rocks in lower Jurassic Series of Lengxi sub-sag. For Lenghu-4, the gas was mainly generated from humus-mature source rocks in lower Jurassic Series of the northern slope of Kunteyi sub-sag. Gas in Lenghu-5 was mainly later filled oil-type gas, which was generated from high matured sapropelics in lower Jurassic Series of Kunteyi sub-sag. Earlier filled coal-type gas was the main part of Mahai, Nanbaxian and Mabei oil-gas fields. Gas source of Mahai was mainly generated from high mature humics in lower Jurassic Series of Yibei sub-sag; for Nanbaxian, the gas was mainly generated from high matured humics in middle-lower Jurassic Series of Saishiteng sub-sag; for Mabei, the gas was mainly generated from humus-mature source rocks in middle Jurassic Series of Yuqia sub-sag.展开更多
For the next exploration direction and integrated evaluation and optimization of targets for the northern continental margin of the South China Sea,this paper proposes the concept of the“total natural gas play system...For the next exploration direction and integrated evaluation and optimization of targets for the northern continental margin of the South China Sea,this paper proposes the concept of the“total natural gas play system”based on the principles of systems theory.Integrating over 60 years of exploration achievements in the four major basins,the paper studies the basic geological conditions,hydrocarbon accumulation models and distribution characteristics of the system.With the core principle of“source-heat controlling natural gas and play-stratigraphy controlling accumulation”,it analyzes the distribution law of natural gas reservoirs covering“intra-sag,sag margin,extra-sag”and multi-stratigraphic sequences.The study shows that under the joint control of source and heat,the northern continental margin of the South China Sea can be divided into two major gas areas:the southern area dominated by coal-type gas and the northern area dominated by oil-type gas,with the former as the main body.Based on the distribution location of hydrocarbon kitchen,the total gas plays are classified into three types:intra-sag,sag margin and extra-sag.In the oil-type gas area of the northern coastal zone,the proportion of intra-sag natural gas is relatively high;in the coal-type gas area of the southern offshore zone,the proportions of intra-sag and sag margin natural gas are relatively large;while the scale of gas accumulation in the extra-sag plays is relatively small.Finally,it is clearly pointed out that the southern offshore zone is the main direction for the next natural gas exploration in the northern South China Sea.Specifically,in the offshore zone,the intra-sag play and middle-deep layers of the sag margin play in the Yingzhong sag should be focused for the Yinggehai Basin;the intra-sag play and sag margin play in the central depression are targets for the Qiongdongnan Basin;the middle-deep layers of the intra-sag play are targets for the Baiyun sag of the Pearl River Mouth Basin.Furthermore,in the northern depression zone of the Pearl River Mouth Basin within the coastal zone,the main exploration directions include the middle-deep layers of the intra-sag play in the Huizhou sag and the middle-deep layers of the intra-sag play in the Enping sag;in the Beibu Gulf Basin,the main directions are the middle-deep layers of the intra-sag play in the Weixinan sag and the middle-deep layers of the intra-sag play in the Haizhong sag.展开更多
基金Financial support from the National Natural Science Foundation of China (No. 40730422)the Priority Academic Program Development of Jiangsu Higher Education Institutions of Chinadata provided by Jurassic Project Department in Research Institute of Petroleum Exploration and Development of China are gratefully acknowledged
文摘The current study tested the gas component and carbon isotopic composition of gas samples from 6 oilgas fields at the northern margin of Qaidam Basin, and established a chart to quantitatively identify the mixing ratio of source-mixed gas. Besides, this research quantitatively investigated the natural gas generated by different types of organic matter. The results show that different ratios of source-mixed gas exist in the 6 oil-gas fields at the northern margin of Qaidam Basin. Among them, Mabei has the highest mixing ratio of coal-type gas, followed by Nanbaxian, Mahai, Lenghu-4, Lenghu-3 and Lenghu-5, with the ratios of coal-type gas 91%, 87%, 83%, 66%, 55% and 36%, respectively. Lenghu-3 and Lenghu-4 oil-gas fields were mainly filled by coal-type gas earlier. For Lenghu-3, the gas was mainly generated from low matured source rocks in lower Jurassic Series of Lengxi sub-sag. For Lenghu-4, the gas was mainly generated from humus-mature source rocks in lower Jurassic Series of the northern slope of Kunteyi sub-sag. Gas in Lenghu-5 was mainly later filled oil-type gas, which was generated from high matured sapropelics in lower Jurassic Series of Kunteyi sub-sag. Earlier filled coal-type gas was the main part of Mahai, Nanbaxian and Mabei oil-gas fields. Gas source of Mahai was mainly generated from high mature humics in lower Jurassic Series of Yibei sub-sag; for Nanbaxian, the gas was mainly generated from high matured humics in middle-lower Jurassic Series of Saishiteng sub-sag; for Mabei, the gas was mainly generated from humus-mature source rocks in middle Jurassic Series of Yuqia sub-sag.
基金Supported by the NSFC-Industry Joint Fund for Innovative Development(U24B2016)China National Science and Technology Major Project(2025ZD1402700)。
文摘For the next exploration direction and integrated evaluation and optimization of targets for the northern continental margin of the South China Sea,this paper proposes the concept of the“total natural gas play system”based on the principles of systems theory.Integrating over 60 years of exploration achievements in the four major basins,the paper studies the basic geological conditions,hydrocarbon accumulation models and distribution characteristics of the system.With the core principle of“source-heat controlling natural gas and play-stratigraphy controlling accumulation”,it analyzes the distribution law of natural gas reservoirs covering“intra-sag,sag margin,extra-sag”and multi-stratigraphic sequences.The study shows that under the joint control of source and heat,the northern continental margin of the South China Sea can be divided into two major gas areas:the southern area dominated by coal-type gas and the northern area dominated by oil-type gas,with the former as the main body.Based on the distribution location of hydrocarbon kitchen,the total gas plays are classified into three types:intra-sag,sag margin and extra-sag.In the oil-type gas area of the northern coastal zone,the proportion of intra-sag natural gas is relatively high;in the coal-type gas area of the southern offshore zone,the proportions of intra-sag and sag margin natural gas are relatively large;while the scale of gas accumulation in the extra-sag plays is relatively small.Finally,it is clearly pointed out that the southern offshore zone is the main direction for the next natural gas exploration in the northern South China Sea.Specifically,in the offshore zone,the intra-sag play and middle-deep layers of the sag margin play in the Yingzhong sag should be focused for the Yinggehai Basin;the intra-sag play and sag margin play in the central depression are targets for the Qiongdongnan Basin;the middle-deep layers of the intra-sag play are targets for the Baiyun sag of the Pearl River Mouth Basin.Furthermore,in the northern depression zone of the Pearl River Mouth Basin within the coastal zone,the main exploration directions include the middle-deep layers of the intra-sag play in the Huizhou sag and the middle-deep layers of the intra-sag play in the Enping sag;in the Beibu Gulf Basin,the main directions are the middle-deep layers of the intra-sag play in the Weixinan sag and the middle-deep layers of the intra-sag play in the Haizhong sag.
