陕甘宁盆地下奥陶统马家沟组层序地层与天然气的关系

Sequence stratigrapgy and its bearings on the gas accumulation in the Lower Ordovician Majiagou Formation, Shaanxi Gansu Ningxia Basin

陕甘宁盆地马家沟组可划分出３ 个层序，每个层序均由海侵体系域及高位体系域所组成，海平面变化是控制层序形成的主要因素。此外，盆地基底构造对层序地层的分布也具有重要的影响，在盆地中部发育浅水层序，在盆地西部及南部则发育较深水层序。在盆地中部浅水层序的高位体系域中，生储盖组合最佳。

The Lower Ordovician Majiagou Formation, Shaanxi Gansu Ningxia Basin may be divided into three sequences, each of which consists of both transgressive and highstand systems tracts. The sea level changes are considered to be the main factors controlling the formation of the sequences. In addition, the basal structures of the basin also have important effects on the distribution of sequence stratigraphy in the formation. Broadly speaking, the shallow water sequences occur in the middle part, whereas the deep water sequences appear in the western and southern parts of the basin. The source reservoir cap rock associations are preferred in the highstand systems tracts of the shallow water sequences in the middle part of the basin, which indicate significant hydrocarbon potential.