徐家围子断陷火山岩气藏主控因素及有利区

Main controlling factors and favorable area prediction of gas reservior of deep volcanic rock in Xujiaweizi fault depression

徐家围子断陷是我国东部富含火山岩天然气藏的重点断陷.探讨徐家围子断陷火山岩气藏基础地质条件和火山岩含气系统,分析火山岩气藏主控因素及耦合关系,揭示火山岩天然气成藏规律.结果表明:徐家围子断陷火山岩气藏控制因素包括优质、成熟的气源岩为火山岩气藏提供充足的气源条件;原生和后期改造型火山岩体为火山岩气藏提供有利的储集空间;基底断裂控制火山岩体的分布并提供天然气高效运移的疏导通道;火山岩气藏成藏主控因素、时空匹配关系控制天然气富集.火山岩气藏主要分布于构造高部位和斜坡带,全区发育原生型火山岩气藏,徐中地区和安达地区发育后期改造型火山岩(风化壳)天然气藏.徐家围子地区存在一定范围的风化壳,厚度在100m左右,主要分布于安达地区和徐中地区;距火山岩风化壳顶面由近及远,单井日产气量从26×104 m3降至8×104 m3,火山岩孔隙度从26%降至8%,风化剥蚀改善火山岩储集性能.

Xujiaweizi fault depression is the key fault-depression of abundant gas-bearing reservoir of the eastern of China.The paper discussed in detail the fundamental gas accumulation and gas-bearing system of volcanic rock in Xujiaweizi fault depression,analyzed the reservoir controlling factor and coupling relationship of volcanic gas,revealed reservoir-forming rule of volcanic gas in Xujiaweizi fault depression.The reservoir controlling factors are as follow:1)high quality,mature source rocks provides ample gas condition for volcanic gas reservoir;2)native and reformation volcanic body provides favorable reservoir space for volcanic gas;3)basement faults control the distribution of volcanic rock body and provide efficient natural gas migration channel dredge;4)time-space matching relation and main controlling factors of volcanic gas reservoir control gas enrichment.Reservoir-forming rule of volcanic gas are:Volcanic gas reservoir are mainly distributed in the structural high position and slope,native volcanic gas reservoirs are widespread distributed in the whole Xujiaweizi fault depression and reformation volcanic(weathering crust)gas reservoir are segmentally distributed in the Xujiaweizi fault depression.And we get the following understanding:there are a range of weathering crust in Xujiaweizi fault depression,the thickness about 100 m,mainly distribute in Anda area and Xuzhong area;From the top surface of the volcanic weathering crust to farness,single well gas output amount fluctuate from 26×104 m3 to 8×104 m3.Volcanic porosity varies from 26%to 8%.Weathering erosion improved volcanic reservoir performance.