鄂尔多斯盆地中东部奥陶系马家沟组沉积相演化模式研究

通过野外露头、岩心和薄片观察,结合测井资料,综合古气候、古沉积格局分析,系统地总结了鄂尔多斯盆地中东部奥陶系马家沟组沉积微相类型,并建立了沉积相演化模式。研究表明:(1)鄂尔多斯盆地中东部马家沟期具有"隆洼相间型"和"平底锅型"两种古沉积格局并存的特征;(2)主要发育9种微相类型,根据不同海平面高度的沉积微相平面组合类型,可将一个完整的海侵—海退旋回细分为海侵初期、中期和末期,海退初期、中期和末期等6个演化阶段;(3)古气候、古沉积格局和海平面升降变化共同控制了马家沟组生储盖分布,指出位于海侵期的东部隆起带及邻近区域发育的颗粒滩和白云岩坪,具有良好的成藏条件,有望成为一个碳酸盐岩勘探新领域。

Sedimentary Facies Evolution Model of Ordovician Majiagou Formation,Central-Eastern Ordos Basin

Based on the observation of outcrops, cores and thin sections, and analysis of logging data and experiment data, the sedimentary microfacies of Ordovician Majiagou Formation in Ordos Basin are studied systematically. Furthermore, the evolution models of sedimentary facies are established by synthetic analysis of paleoclimate and paleo-sedimentary patterns. It is indicated that: (1)There are two types of paleo-sedimentary framework of Majiagou Formation: sag-and-swell type and single-sag type; (2)Nine types of microfacies are developed in Ordovician Majiagou Formation. According to the combination of these sedimentary microfacies in the lateral direction at different sea level, a complete transgressive-regressive cycle can be subdivided into six stages: early, mid and late stages of transgression and early, mid and late stages of regression; (3)The distribution of sources, reservoirs and cap rocks of Majiagou Formation is controlled by paleo-climate, paleosedimentary pattern and sea-level fluctuation. It is concluded that the grain bank and dolomite flat developed in eastern uplifted zone and adjacent areas during transgressional period have a good reservoir-forming condition and can be expected to be a new favorable potential area of carbonate exploration.