松南长岭断陷火山岩亚相约束下的气层测井识别评价

松辽盆地长岭断陷营城组火山岩包括4相12亚相;优质储层主要见于爆发相热碎屑流、喷溢相上部和下部、火山通道的火山颈等4亚相.火山岩气藏普遍含CO2,部分为纯CO2气藏.基于26口重点探井的自然伽马、电阻率、声波时差和中子等测井参数分析,建立了岩相亚相-测井识别模式;进而在亚相约束下,用声波-中子-密度三种孔隙度叠置图进行...

Log identification of volcanic gas zone under volcanic facies in Changling sag, south Songliao Basin

The volcanic gas-reservoir of Changling sag is an important deep exploration and development goal in South Songliao Basin. The volcanic rock lithology and lithofacies of Yingcheng Formation in the research area are complicated and multiple, including four facies and twelve subfacies. Volcanic gas-reservoirs generally contain CO₂ gas and the CO₂ contents are high in part wells. All of these make some difficulties in gas zone accurate identification. Through the analysis of natural gamma ray, electrical resistivity, acoustic time, neutron porosity and other parameters of 26 wells, the logging identification models of hot debris flow subfacies, upper subfacies, lower subfacies and diatreme subfacies are made, which control high quality reservoirs development. The method of logging accurate identification of gas zone is discussed under the restriction in the subfacies. Based on logging data, the three porosity overlay figures of acoustic, neutrons and density are drawn, and the one with acoustic porosity greater than neutrons porosity indicates the possible gas zone. Three types of the two kinds of porosity overlay curves are recognized: high porosity-double porosity similar type, low porosity-double porosity dissimilar type and low porosity-double porosity similar type. The subfacies are identified in possible gas drilling sections. The possible gas drilling sections can be interpreted as gas zone, bad gas zone or dry zone by corresponding relationship between subfacies types and overlay curves types. Hydrocarbon gas zone(CH₄)or non-hydrocarbon gas zone is identified by the method of three porosity overlaying. The difference between acoustic porosity and density porosity is small in hydrocarbon gas zone, but it is very different in CO₂ gas zone. This method can improve the accuracy for identification of volcanic gas zone.