鄂尔多斯盆地靖边西南马五5储层特征及主控因素分析

Characteristics and main control factors of M5_5 submember of Majiagou Formation in southwest of Jingbian Gasfield,Ordos Basin

奥陶系马家沟组马五_5亚段作为鄂尔多斯盆地油气勘探的新层段已经取得了突破,显示出巨大的勘探潜力,马五_5储层特征及主控因素的研究有助于进一步扩大鄂尔多斯盆地马五_5的勘探成果。通过岩心观察、薄片鉴定、物性分析等手段,对靖边气田西南部奥陶系马五_5的白云岩储层特征进行研究,并对影响储层发育的主控因素进行探讨。研究表明:储集层岩性主要为粗粉-细晶白云岩及泥晶白云岩,属于白云岩型储层;储集空间以晶间孔和粒间溶孔为主,具有低孔、低渗特征;优质储层的发育明显受沉积相、成岩作用和岩溶古地貌的控制;颗粒滩为马五_5储层发育的有利微相带;溶解-中等充填粒(晶)间孔白云岩相为有利成岩相带;沟槽对储层的岩溶改造作用改善了储集空间并提供了天然气运移的通道。最终优选出三个Ⅰ类有利区。研究成果对于该区天然气勘探及储层预测具有重要指导意义。

In recent years,taken M5 5 submember of Ordovician Majiagou Formation as new layers for oil-gas exploration of Ordos Basin,the breakthrough has been obtained,indicating huge exploration potential.So the studies on reservoir characteristics and controlling factors are helpful to further enlarge the exploration achievements of M5 5.According to the observation of core samples and identification of thin section and physical analysis,it was carried out studies on reservoir characteristics of dolostone and main control factor affecting on reservoir development for M5 5 submember of Ordovician Majiagou Formation in southwest of Jingbian Gasfield.Research results indicated that reservoir lithology belongs to dolostone type reservoir,which mainly consists of siltcrystal-micrite dolostone and micrite dolostone.The reservoir spaces,which are intercrystalline pores and intercrystalline dissolved pores in dominant,have characteristics of low porosity and low permeability.The development of high quality reservoirs is obviously controlled by sedimentation,diagenesis,and palaeogeomorphology of karsts.The grainstone shoals are favorable sedimentary microfacies and the dolostone tidal flats are favorable diagenesis facies.The reservoir space is improved by the karst of reservoir reformed by groove,providing a natural migration path.Finally,three favorable exploratory areas of classⅠwere optimized.The research results have an important guiding significance to natural gas exploration and reservoir prediction in the study area.