鄂尔多斯盆地西南缘镇泾油田长6-2沉积相研究

SEDIMENTARY CHARACTERS OF CHANG 6-2 MEMBER OF ZHENJING OIL FIELD IN SOUTHWEST ORDOS BASIN

延长组长6-2是鄂尔多斯盆地西南缘镇泾油田的一个重要勘探层位.通过岩心观察、测井资料、薄片研究、粒度分析,对镇泾油田长6-2沉积微相进行了深入研究.认为该区长6-2由一个完整的中期基准面旋回组成,水下分流河道主要发育在中期基准面缓慢上升初期和快速下降阶段,由于水下分流河道的强烈侵蚀作用,河口坝砂体不发育.中期基准面缓慢上升初期的河道具有深而窄的特点,砂体横向变化快,勘探难度大,而与之相对的是中期基准面快速下降阶段,水下分流河道具有厚而广的特点,为本区最为有利的勘探目的层.通过对不同可容空间下水下分流河道砂体厚度与河道宽度的研究,发现其具有很好的相关性,得出该区的砂体厚度与河道宽度的经验公式,为下一步勘探开发提供了强有力的理论依据.

Chang 6-2 member of Yanchang Formation is an important explored layer of Zhenjing oil field in southwest Ordos basin. We researched sedimentary facies of Chang 6-2 member of Zhenjing oil field carefully by looking core, researching flake, analyzing grain size. It is showed that Chang 6-2 member is composed of a whole middle base level cycle, subaqueous distributary channel appears in the phase of middle base level ascending slowly and descending quickly. Mouth bar is little because of strong erosion of subaqueous distributary channel. Channel becomes deep and narrow in the phase of middle base level ascending slowly, and channel sandstones change quickly horizontally with difficult exploration. On the contrary, subaqueous distributary channels become thick and spread in the phase of middle base level descending quickly, so they become favorable explored layers in this area. We find good relationship between subaqueous distributary channel sandstone thickness and channel width of different accommodation, and get experienced equation of width and thickness, then offer powerful theory basement for next exploration and development.