鄂尔多斯盆地西区油田延长组长8储层特征及影响因素

Influential factors and characteristics of Chang 8 Formation reservoir in Xiqu Oilfield, Ordos Basin

通过岩心观察、测井及各类分析测试资料,对西区油田长8储层岩石学、孔隙结构和储层物性等特征进行了研究.结果表明:研究区延长组长8储层为典型的特低孔-特低渗储层,层内非均质性较强,主要呈强-中等非均质型;储层砂体为成分成熟度和结构成熟度都较低的岩屑质长石砂岩和长石质岩屑砂岩;储集空间主要为粒间孔和长石溶孔;孔隙结构类型以小孔中细喉型和小孔微细喉型为主;研究区长8储层物性受沉积微相、孔隙结构、成岩作用的共同影响;不同沉积微相储层的物性差异较大;成岩作用对储层物性的影响具有两面性,压实作用、胶结作用导致储层致密,物性变差;溶蚀作用与烃类充注改善了储层物性.

Based on core observations, logging data and sample tests, the reservoir petrology, pore structure, physical properties and other reservoir characteristics of Chang 8 in Xiqu Oilfield were discussed and the research demonstrated the reservoir of Chang 8 to be of especially low porosity-low permeability. The intraformational heterogeneity is stronger, and the main property is of strong-medium heterogeneous type. The reservoir is constituted of lithic feldspathic sandstones and feldspathic lithearenite sandstones with a low compositional and textural maturity. The pore space is of mainly intergranular pores and feldspar solution pores. The pore structure is of small holes with micro throats. The main factors contributing to the physical properties are deposition property and the diagnostic and accumulation properties are various in the different sediments. Micro-facies digenesis has altered the physical properties in two opposite aspects. Compaction and cementation have reduced the physical properties, and dissolution and hydrocarbon filling have made it better.