Evoluation Of Volcanic Reservoir And Gas-water Relation In Songnan Gas Field Of Songliao Basin

Songnan Gas Field locating in the central sag zone within Changling Fault Depression of Songliao Basin is a major breakthrough of volcanic rocks in the deep reservoir exploration of Sinopec. Volcanic gas reservoir is extremely special. The complex geological conditions, rapid changes in lithology lithofacies, reservoir development of micro-cracks, poor physical properties, strong reservoir heterogeneity, and complex gas-water relation, unconspicuous gas-water interface, water-flooded in the development are the bottleneck problems of restricting volcanic gas reservoir effective exploitation. In order to resolve classification evaluation and prediction of volcanic reservoir and gas-water distribution, the author have studied volcanic lithology, lithofacies and characters of reservoir in Yingcheng Formation. Based on the above-mentioned study, we can conclude:Volcanic lithofacies in the study area are divided into two groups, that is lava and volcaniclastic rock. Lava mainly contains acid ~ in acidic rhyolite, dacite, etc; and volcaniclastic rocks consist of ignimbrite, rubble ignimbrite, rhyolitic volcanic breccia, etc. Volcanic lithofacies in the study area are composed by eruption facies and effusion facies. Effusion facies of the reservoir properties are better than that of eruption facies , Which is major volcanic gas reservoir of Yingcheng Formation.Types of pore in the study area are mainly original gas-pore, secondary dissolved pore (intergranular dissolved pore, matrix emposieu and porphyroblast-hole), secondly are intergranular cracks and fracture pore; cracks make up of high-lead joints and micro-cracks. Reservoir of Yingcheng Formation is divided into I-1, I-2, II, III-1, III-2. I type at the top of effusion facies have better property and farther horizontal distribution; II type of hot debris-flow facies in eruption facies have medium property with vertical thickness; III type with poor property developing in central and lower of effusion facies are close to air-water interface and bigger exploitation risk.The study area is not a uniform gas reservoir. Deep fault and volcanic eruptions had affected the distribution of gas reservoir, which cause different gas reservoir has its own independent air-water interface and distribution. The conclusions have significant instruction for next geometric arrangement of wells.