松辽盆地南部长岭断陷营城组火山岩天然气成因与成藏

Origin and Accumulation of Natural Gas in Volcanics of Yingcheng Formation of Changling Fault Depression,Southern Songliao Basin

为了搞清长岭断陷混合气、CO2成因,寻找烃类气聚集区带,以火山岩岩石学、油气成藏理论为指导,利用地震、测井、综合录井、天然气化验分析及相关测试资料,采用天然气成因图版、激光拉漫光谱、埋藏史、天然气成藏演化等技术方法,开展了混合气、CO2成因及气源特征研究,进行了成藏条件分析,探讨了成藏组合及模式。结果表明:(1)长岭1号烃类气为有机与无机烷烃混合气,有机成因气为同源不同期的煤成气;(2)长岭断陷CO2含量大于20%,N2含量4.8%~7.8%,δ13CCO2为-0.006 8‰^-5.45‰,3He/4He为2.61×10-6~2.91×10-6,R/Ra为1.86~2.29,为岩浆-幔源成因气;(3)长岭1号混合气成藏的关键要素是哈尔金断洼烃源岩、近火山口相火山岩、古构造背景、沟通气源的哈尔金大断裂;(4)CO2富集成藏与高古地温梯度、多期次喷发火山岩规模及沟通上地幔的区域深大断裂有关。对长岭断陷火山岩天然气勘探部署具有重要的指导作用。

In order to clarify the origin of the mixturegas and CO2 in Changling Fault Depressionand explore for the hydrocarbon accumulation zones,guided by volcanic petrology and hydrocarbon accumulation theories,the genesis of the mixturegas and CO2 and the characteristics of gas source were studied,the accumulation conditions of the mixture gas were analyzed,andthe combinations and modes of hydrocarbon accumulation were discussed using seismic,logging,comprehensive mud logging,natural gas chemical analysis and related test data and by means of such technical methods as natural gas genesis map,laser diffuse spectroscopy,burial history,natural gas accumulation evolution. The results show that：（1） Changling No. 1 hydrocarbon gas is a mixture of organic and inorganic alkanes,and the organic origin gas is the coal gas with the same source and different stages.（2） CO2 content of the mixture gas in Changling Fault Depression is more than 20%,N2 content is 4. 8% ~ 7. 8%,δ13 CCO2 is-0. 006 8‰ ^-5. 45‰,3 He/4 He is（ 2. 61 ~ 2. 91） × 10-6,R/Ra is 1. 86 ~ 2. 29,the mixture gas belongs to a magmatic-mantle source gas.（3）The key elements of Changling No. 1 mixture gas reservior are Harjin fault depression source rock,volcanic rocks near the crater,paleostructural background,and Harjin fault that communicates with gas source.（4） the accumulation of CO2 isassociated with high paleo-geothermal gradient,the multi-stage eruption scale of volcanic rock and the regional deep faults that communicate with the upper mantle. The above understandings play an important guiding role in the natural gas exploration and deployment of volcanic rocks in Changling Fault Depression.