准噶尔盆地西泉地区石炭系火山岩型油藏形成及分布

The Formation and Distribution of Volcanic Reservoirs in the Xiquan Area of Junggar Basin

准噶尔盆地西泉地区在构造上位于北三台凸起西斜坡,是有利油气聚集区。虽然已取得了一些勘探成果,但该区油藏控制因素复杂,纵横向分布规律认识不清,致使探明程度低、勘探难度大。利用钻井、测井、录井、试油、岩芯分析化验等资料,结合地震资料,查明了该区石炭系储层岩石学特征、储层特征。研究结果表明:西泉地区石炭系火山岩主要为火山熔岩类、火山碎屑岩类;火山岩储层物性北部较差,南部较好,有利储层主要是喷发相火山角砾岩、溢流相安山岩、英安岩等。该区油藏分布的主要控制因素:1)垂向上油藏主要分布于风化壳附近; 2)岩性的侧向变化控制了油藏的平面分布范围; 3)不整合面的发育与油藏的分布关系密切。进一步阐明了研究区油藏的分布规律,油气主要聚集于不整合面附近,且呈北东南西向条带状分布。油层的纵向分布与不整合面的风化淋滤带的深度有关,南北差异较大,储层的非均质性影响油藏的连片分布。

The Xiquan area is tectonically at the west ramp of the Beisantai salient and is suitable for oil and gas accumulation.Although a few Carboniferous reservoirs were found in past decades,because of the complex controlling factors and confused distribution in both longitudinal and horizontal directions of reservoirs in this area,the proved rate is low,and further exploration is difficult.This paper clarifies the petrologic and reservoir characteristics of Carboniferous reservoirs.The results include that Carboniferous reservoirs in the Xiquan area consist mainly of lava and pyroclastic rock;that reservoir physical properties in the South are better than in the North;and that favorable reservoirs have mainly developed in eruptive volcanic breccia and effusive facies of andesite and dacite.On this basis,the main controlling factors of reservoir distribution have been clarified:1)reservoirs mainly concentrate near the weathering crust in the vertical profile,2)the lateral variation of lithology controls the plane distribution of the reservoirs,and 3)reservoir distribution is closely related to the development of unconformities.In addition reservoir distribution laws have been summarized:oil and gas mainly concentrate near unconformities and stretch from Northeast to the Southwest like stripes;the vertical distribution of oil layers is related to the depth of eluvial zones of unconformity and is different between South and North;and heterogeneity influences contiguous distribution in the reservoir plane.