Reservoir Evaluation And Natural Gas Accumulation Condition Analysis Of Chang Shen-6 Well

ChangShen-6 well is a wildcat well in Jilin Oilfield of PetroChina Company Ltd,which is located in the southeast, 3.0 km away from the C well in Qian’an County,Songyuan city, Jilin province and deployed in southern subsag of Heidimiao structure in Changling fault depression of Songliao Basin.The article is based on the research of ChangShen-6 well, its volcanic reservoir lithology, lithofacies, reservoir space types, reservoir properties and gas genesis and composition are determined according to the technical means of core observation, thin section identification, FMI Well Logging, NMR Logging Technique and mercury intrusion. Besides, the research reveals the spatial distribution and developmental status of volcanic rocks, the contribution of different causes of natural gas to volcanic gas reservoirs and controlling factors of different types of gas reservoirs distribution.Thus the volcanic reservoir forming rules are summarized. From rational development of excellent reservoir and dividing of favorable facies zone, a set of prediction and interpretation of volcanic reservoir and gas origin is established. Understanding and major achievements are as follows:Yingcheng Formation of ChangShen-6 well is divided into five lithology :volcanic breccia, volcanic agglomerate, rhyolite, rhyolitic tuff, tuff, with volcanic breccia and rhyolite the main lithology, while Denglouku Formation is divided into six lithology: unequal particle quartz sandstone, siltstone, silty mudstone, mudstone,argillaceous siltstone, sandy conglomerate, fine sandstone, with siltstone the main lithology. The whole Yingcheng Formation of ChangShen-6 well is volcanic rock which is divided into two sedimentary facies: burst facies and effusive facies, while braided channel dominates mainly in Denglouku Formation.Volcanic reservoir of ChangShen-6 well mainly develops in rhyolite, tuff and volcanic breccia, crack mainly develops rhyolite and tuff in the middle of volcanic,while pore is in volcanic breccia and tuff. The main reservoir type is pore-fractured.The merits and demerits of the reservoir is that burst facies dominates the best, while volcanic debris flow facies is better than effusive facies. Reservoir develops mainly in volcanic debris flow facies and effusive facies.Clastic rock gas reservoir of Denglouku Formation in ChangShen-6 well belongs to structural lithological reservoir. Volcanic reservoir in Yingcheng Formation below is classified as fornix gas reservoir. Inorganic gas holds large proportion of between 57.1% ~ 64.7% in Alkane mixture, while organic origin gas is less than 42.9%.Mainly inorganic origin CO2 in Yingcheng Formation takes up 87.8%~96.5%. By establishing ChangShen-6 well accumulation model, accumulation model of deep fracture creep and shallow volcanic conduit infill injection is determined.