琼东南盆地中央峡谷天然气成藏特征及其主控因素  

Characteristics and Key Controlling Factors of Natural Gas Accumulation in the Central Submarine Canyon,Qiongdongnan Basin

作　　者：许怀智[1,2] 张迎朝 林春明[1] 裴健翔 刘云芝 

机构地区：[1]内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院,南京210046 [2]中海石油(中国)有限公司中上海分公司,上海200030 [3]中海石油(中国)有限公司湛江分公司,广东湛江524057

出　　处：《地质学报》2014年第9期1741-1752,共12页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41272124、41402092);国家科技重大专项“大型油气田及煤层气开发项目”(编号2011ZX05025002)资助的成果

摘　　要：基于地震、测井、岩芯、岩屑和天然气样品分析化验等资料,研究了中央峡谷天然气成藏特征,探讨了成藏主控因素与成藏模式.研究结果表明,晚中新世早上新世沿琼东南盆地中央坳陷发育一条大型海底峡谷,称之为中央峡谷,峡谷内充填了多期相互叠置的浊积砂岩,平均孔隙度为15％～33％,渗透率为11×10^-3～971.3×10^-3μm^2,为较好的储层;发育了岩性和构造岩性复合两大类圈闭.峡谷的气源来自于崖城组的煤系地层,属于煤型气.烃源岩的有机质类型为Ⅱ2和Ⅲ型,以Ⅲ型为主;热演化程度处于成熟 高成熟阶段,晚中新世上新世达到生烃高峰.琼东南盆地中央坳陷是一个高温高压的坳陷,实测地温梯度平均值高达4.2～4.6℃/100m,实测压力系数为1.20～2.15.在高温高压的环境下,盆地内孕育众多的底辟构造,而峡谷下伏的底辟构造与谷内相互叠置的复合砂体在空间上有效的配置构成了天然气垂向与侧向运移的输导体系,成为峡谷天然气成藏的关键因素.Based on seismic data, logging data, analytical data of cores, cuttings and nature gas samples, the characteristics of the natural gas accumulation, key controlling factors and accumulation model of the natural gas accumulation of the central submarine canyon are studied. The results demonstrate that a large old submarine canyon, named the central canyon, developed along the axis of the central depression of Qiongdongnan basin during Late Miocene to Early Pliocene. The canyon is filled with multiphase turbidite sandstones, the average porosity of which ranges from 15% to 33% and permeability range from 11× 10^-3 to 971.3× 10^-3 μm^2 , suggesting high-quality reservoirs for natural gas. Two kinds of traps developed in the canyon- the lithologic trap and the structural-lithologic complex trap. The natural gas in the turbitide sandstones sources from coal layers of the Yacheng Formation, and is coal-type one. Organic matter of the source rock is dominated with type Ⅲ, with minor Type Ⅱ2. Thermal evolution of the source rock indicates that the hydrocarbon-generating potential of the source rock reached its maximum in Late Miocene to Pliocene, and are presently in mature and highly-mature stage. The central depression of Qiongdongnan Basin is a high-P and high-T depression, with the average geothermal gradient of 4.2℃/ 100m to 4.6℃/100m and pressure coefficients of 1.20 to 2.15. Under the high-T and high-P condition, many diapiric structures occurred in the basin, while combination of underling diapiric structures with complex sandstones formed effective channels of vertical and lateral migration of the gas, which is the key factor for accumulation of the gas in the turbidite sandstones filled the central canyon.

关 键 词：南中国海 琼东南盆地 中央峡谷 天然气成藏 底辟构造 

分 类 号：P618.13[天文地球—矿床学]