大型坳陷湖盆定量化沉积相编图新方法——以鄂尔多斯盆地中部长7油层组为例

A new quantitative method of sedimentary facies mapping of large lacustrine depression:a case from Chang 7 reservoir in central Ordos Basin

为满足现今非常规油气勘探需求,提高沉积相编图的精度和效率,以鄂尔多斯盆地三叠系延长组长7油层组为研究对象,对其沉积岩相、分布特征、组合规律、演化趋势等进行了系统研究,综合录井图分析表明:长7油层组共发育10种岩性,其中以细砂岩、泥质粉砂岩、粉砂质泥岩、泥岩和页岩等5种岩性为主,占地层厚度的97%左右。通过岩心观察和统计分析,建立了每种沉积微相或亚相对应的5种主要岩性厚度比例组合,提出了利用主要岩性厚度比例组合实现定量化沉积相编图的新方法。利用该方法在长7油层组主要岩性厚度百分比等值线叠加图上,识别并精细划分出各类沉积微相或亚相,包括三角洲平原分流河道、三角洲前缘水下分流河道、水下分流间湾、远砂坝、河口坝、前三角洲、砂质碎屑流、浊流和半深湖—深湖等。

In order to meet the needs of unconventional hydrocarbon exploration nowadays and improve the accuracyand efficiency of sedimentary facies mapping,the lithofacies classification,facies distribution,lithologycombination proportion and sedimentary environment evolution of Triassic Chang7reservoir in Ordos Basinwere analyzed.There are ten types of lithology recognized from the sieve residue log plot.Five of them are dominated,including fine sandstone,argillaceous siltstone,silty mudstone,mudstone and shale,of which the thicknessis about97%of the strata.Based on core observation and statistical analysis,the thickness composition ofeach microfacies with the five types of lithology was established,which can be used to implement quantitativesedimentary facies mapping.By overlapping the thickness percentage isoline maps of the five types of lithologyin Chang7reservoir,various microfacies can be intensively identified,including delta plain distributary channel,delta front subaqueous distributary channel,subaqueous distributary channel,distal bar,mouth bar,prodelta,debris flow,turbidite,semi-deep to deep lacustrine.