本文選題：漂白砂巖 + 不整合結構��； 參考：《地質(zhì)學報》2017年06期

【摘要】：鄂爾多斯盆地東北部侏羅系延安組頂部的砂巖漂白現(xiàn)象是油氣運移逸散的重要證據(jù),但前人僅從油氣蝕變角度對漂白砂巖進行研究,而忽視了其形成地質(zhì)環(huán)境。漂白砂巖分布在不整合面之下的風化殼中,指示不整合結構是其形成的重要地質(zhì)背景。本文結合野外觀察、礦物學和地球化學分析,對該區(qū)侏羅系不整合結構特征進行重點剖析,并對漂白砂巖成因進行探討。結果表明,研究區(qū)侏羅系不整合風化黏土層不發(fā)育,不整合結構可劃分為具半風化巖石和缺失半風化巖石兩種類型。半風化層上部砂巖礦物成分以石英和高嶺石為主,溶蝕孔隙發(fā)育,黑云母普遍發(fā)生高嶺石化,砂巖中堿、堿土金屬元素(K,Na,Ca,Mg)大量流失。半風化層下部砂巖鉀長石含量偏高,黑云母不完全蝕變?yōu)樗谠颇?砂巖中殘留K和Mg。風化殼內(nèi)細碎屑沉積巖物性條件差,與外部流體溝通有限,早期風化蝕變和后期烴類蝕變均較弱。漂白砂巖中的高嶺石主要為風化淋濾的產(chǎn)物,砂巖因風化作用物性得以改善而成為重要的油氣運移通道,同時富集鐵氧化物而呈紅色。風化殼內(nèi)紅色砂巖后期受到烴類的還原蝕變而發(fā)生褪色漂白,由于先后經(jīng)歷了風化淋濾和烴類還原兩種蝕變作用,延安組頂部砂巖表現(xiàn)為膠結程度差、易遭受流水侵蝕的特性。碎屑巖古風化殼中的漂白現(xiàn)象是識別不整合結構參與油氣運移成藏的重要標志。
[Abstract]:The phenomenon of sandstone bleaching at the top of Jurassic Yanan formation in northeastern Ordos Basin is an important evidence of oil and gas migration and dissipation. Bleached sandstone is distributed in the weathered crust below the unconformity surface, indicating that the unconformity structure is an important geological background for its formation. Combined with field observation, mineralogical and geochemical analysis, the unconformity structure characteristics of Jurassic in this area are analyzed emphatically, and the origin of bleached sandstone is discussed. The results show that the unconformable weathered clay layer of Jurassic in the study area is not developed and the unconformity structure can be divided into two types: the semi-weathered rock and the missing semi-weathered rock. The mineral composition of sandstone in the upper part of the semi-weathered layer is mainly composed of quartz and kaolinite, the dissolution pores are developed, kaolinite is generally occurred in kaolinite, alkali and alkali earth metal elements (K _ (Na) Na ~ (2 +) (mg) are largely lost in sandstone. The content of potassium feldspar in the sandstone of the lower part of the semi-weathered layer is high, the biotite is not completely eroded into hydrobiotite, and K and mg remain in the sandstone. The physical properties of fine clastic sedimentary rocks in weathering crust are poor, the communication with external fluids is limited, and the early weathering alteration and late hydrocarbon alteration are weak. The kaolinite in bleached sandstone is mainly the product of weathering and leaching. Because of the improvement of weathering physical properties, kaolinite becomes an important hydrocarbon migration channel and is red with the enrichment of iron oxides. The red sandstone in weathering crust is decolored and bleached by hydrocarbon reduction and alteration in late stage. Because of weathering leaching and hydrocarbon reduction alteration successively, the top sandstone of Yan'an formation is characterized by poor cementation degree and easy to be eroded by flowing water. The bleaching phenomenon in clastic paleo-weathering crust is an important indicator to identify unconformity structure and participate in hydrocarbon migration and accumulation.
【作者單位】： 西安石油大學地球科學與工程學院;西北大學地質(zhì)學系大陸動力學國家重點實驗室;中國海洋石油(中國)有限公司天津分公司;
【基金】：中國地質(zhì)調(diào)查局項目(編號12120114009201) 國家自然科學重點基金項目(編號41330315,91214301) 西北大學研究生自主創(chuàng)新項目(編號YZZ13013)聯(lián)合資助成果
【分類號】：P534.52;P618.13

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