CAJ | 학술논문

野外露头剖面和井下岩心的岩石学与岩相组合、沉积特征与岩相标志、室内砂岩碎屑矿物组成及其平面分布规律的研究结果表明,鄂尔多斯盆地东部盒8致密砂岩以岩屑砂岩为主,其次为岩屑石英砂岩,主要为深灰色、灰色、灰白色中砂岩和粗砂岩.研究区从北到南依次为冲积扇、辫状河及辫状河三角洲沉积体系.冲积扇以扇中和扇端为主,主要由冲积水道块状构造含砾粗砂岩组成.往南演化为辫状河沉积,主要包括河道砂坝和泛滥平原微相,其中河道砂坝为其骨架相,由大型交错层理和平行层理发育的粗砂岩和含砾粗砂岩组成.南部发育辫状河三角洲平原和前缘沉积,进一步划分出分流河道、泛滥平原、水下分流河道和分流间湾微相,其中分流河道及水下分流河道为其骨架相,类似于河道砂坝沉积,主要由板状、槽状交错层理粗砂岩及中-细砂岩组成,纵向上多期砂体叠置,横向上叠合成片,成为盒8致密砂岩气藏的良好储集层.
야외로두부면화정하암심적암석학여암상조합、침적특정여암상표지、실내사암쇄설광물조성급기평면분포규률적연구결과표명,악이다사분지동부합8치밀사암이암설사암위주,기차위암설석영사암,주요위심회색、회색、회백색중사암화조사암.연구구종북도남의차위충적선、변상하급변상하삼각주침적체계.충적선이선중화선단위주,주요유충적수도괴상구조함력조사암조성.왕남연화위변상하침적,주요포괄하도사패화범람평원미상,기중하도사패위기골가상,유대형교착층리화평행층리발육적조사암화함력조사암조성.남부발육변상하삼각주평원화전연침적,진일보화분출분류하도、범람평원、수하분류하도화분류간만미상,기중분류하도급수하분류하도위기골가상,유사우하도사패침적,주요유판상、조상교착층리조사암급중-세사암조성,종향상다기사체첩치,횡향상첩합성편,성위합8치밀사암기장적량호저집층.
Studies of the petrology, facies assemblages, sedimentary and facies characteristics by typical outcrops and well cores as well as detrital minerals in sandstones and their distribution characteristics indicate that the tight sand of He 8 formation in eastern Ordos Basin is mainly lithic sandstone and subordinately lithic quartz sandstone whose colors are dark gray,gray and grayish white,with the grains being medium sand and coarse sand. There develop three sedimentary systems from north to south which include alluvial fan, braided channel and braided delta. Alluvial fan facies involve chiefly middle-fan and margin-fan subfacies which consist of gravel grit which exhibits massive structure and was derived from alluvial channel. There exists river deposition southward which includes river channel sand dam microfacies and floodplain microfacies, in which the river channel sand dam constitutes the framework made up of grit and gravel grit that exhibit cross stratification and parallel stratification structure. In the south of the study area braided delta plain and braided delta front are developed, in which distributary channel, flood plain, subaquatic distributary channel and interchannel mi-crofacies can be recognized. Among them, the distributary channel and subaquatic distributary channel are skeletons which are analo- gous to river channel sand dam and consist of grit and medium-fine sandstone assuming tabular cross bedding and trough cross stratifi-cation structure. The sand bodies are superimposed upon each other vertically and jointed into pieces horizontally, thus serving as fa-vorable reservoirs for He 8 tight sand gas accumulation.