准连续型致密砂岩气藏地质条件和成藏特征——以鄂尔多斯盆地中部上古生界山西组为例

摘要

With massive data on well drilling,well logging,geological logging and production testing,combined with core observation and wafer analysis,the lithology,diagenesis,physical properties and pore characteristics of quasi-continuous tight sand reservoirs of Shanxi Formation of the upper Paleozoie in the Ordos Basin were analyzed comprehensively,and source rocks,reservoir,reservoir cap rock assemblagecharacteristics and forming models were studied in reservoir to probe into the forming characteristics of the Shanxi Formation.The results showed that the Shanxi Formation of the upper Paleozoic in the Ordos Basin belongs to the category of quasi-continuous tight sand gas reservoirs,and in early Cretaceous a great amount of hydrocarbon source rocks generated into gas.The formation has the characteristics of a near source reservoir,quasi-continuous distribution of sand,a tight reservoir,a number ofdiageneses,complex pore-throat structure,poor physical properties and a favorable type of source rocks.The lower parts of the Shanxi Formation has been mainly developed from wide premium source rocks and its upper parts are of mostly tight reservoirs.Gas migrates to reservoirs through micro fractures and is quasi-continuously distributed.A comprehensive analysis of the quasi-continuous tight sand gas of the Shanxi Formation of upper Paleozoic in the Ordos Basin revealed huge potentials and superior exploration prospects.%通过大量钻井、测井、录井以及试气资料,结合岩心观察和薄片鉴定,对鄂尔多斯盆地上古生界山西组准连续型致密砂岩储层的岩石学特征、成岩作用、物性特征和孔候特征进行综合分析,并对山西组的成藏特征从烃源岩特征、储层特征、储盖组合特征以及成藏模式4个方面进行研究.结果表明:鄂尔多斯盆地上古生界山西组属于准连续型致密砂岩气藏,烃源岩在早白垩世末大量生气,具有近源成藏、砂体大面积准连续分布、储层致密、成岩作用类型多、孔喉结构复杂、物性普遍较差、烃源岩类型好等特征.山西组下部主要广覆式发育优质烃源岩,上部主要为致密储层,天然气通过微裂缝进入致密储层中进而成藏,在地层中呈准连续分布.综合分析鄂尔多斯盆地上古生界山西组准连续型致密砂岩气资源潜力大,具有广阔的勘探前景.