王府断陷小城子气田火石岭组气藏天然气成藏模式及富集规律

Natural gas accumulation models and enrichment patterns of the Huoshiling Fm reservoirs in the Xiaochengzi gas field, Wangfu fault depression, Songliao Basin

松辽盆地王府断陷小城子气田具有上千亿立方米的天然气储量规模,其中,以上侏罗统火石岭组原生气藏的储量规模为最大。为了更有效地指导该区天然气勘探部署,从地层、构造、岩性—岩相和含气性等方面对该区火石岭组气藏的成藏特征和富集规律进行了研究,总结了天然气成藏模式。结果表明:(1)火石岭组气藏发育下部和上部两套含气层系,下部含气层系分布在粗安岩段上部,上部含气层系主要分布在流纹岩段;(2)流纹岩段最有利于天然气成藏,但天然气成藏的主体层段却在粗安岩段;(3)天然气主要富集在火山口杂岩相带,其次是火山斜坡相带;(4)山东屯构造带是天然气的主要富集区,在南北方向表现出分区性,主要包括3个成藏区,即X12井成藏区、X14井—X13井—X18井成藏区和X4井成藏区;(5)共有4种成藏模式,即反转背斜—地层成藏、断块成藏、岩性—断块成藏和断块—反转背斜—地层复合成藏,其中以断块成藏和岩性—断块成藏模式为主;(6)具有"断控—层控—体控"复合型天然气聚集规律。

The geological natural gas reserves of the Xiaochengzi gas field in the Wangfu fault depression, Songliao Basin, amounts to more than 100 billion ma, among which the primary gas reserves in the Late Jurassic Huoshiling Fm are in the greatest scale. To have a better exploration planning in this study area, we discussed the characteristics of gas accumulation and enrichment patterns of the Hu-oshiling Fm gas reservoirs in the Wangfu fault depression, and summarized accumulation models in terms of stratigraphy, structure, li- thology-lithofacies, gas-bearing properties, etc. The findings were obtained as follows. ① The Huoshiling Fm gas reservoirs contains two suites of gas-bearing series, the bottom one distributes in the upper part of the andesitoid member, and the upper one mainly distributes in the rhyolite member. ② Rhyolite is the most favorable rock type for gas accumulation, while andesitoid is the main part for gas accumulation. ③ Natural gas is mainly enriched in areas of crater facies, next, in areas of volcanic slope facies. ④ The Shandongtun structural belt is the main area for natural gas accumulation, and the gas reservoirs can be divided into three accumulation areas through wells from the north to the south, i.e. Well X12, Wells X14-X13-X18 and Well X4. ⑤ Four kinds of gas accumulation models were summarized, in- cluding reversed anticline-stratigraphy accumulation model, fault block accumulation model, lithology-fault block accumulation model, and fault block-reversed anticline-stratigraphy accumulation model. Fault block accumulation model and lithology-fault block accumulation model are the main types. ⑥ Gas accumulation in the Wangfu fault depression is controlled by fault, stratigraphy and volcanic edifice together.