塔中地区上奥陶统良里塔格组白云石化作用成因机理

发布时间：2018-03-27 23:32

本文选题：塔里木盆地中部　切入点：晚奥陶世　出处：《天然气工业》2017年03期

【摘要】：上奥陶统良里塔格组是塔里木盆地中部地区(塔中)重要的油气储集层,其主体岩性为石灰岩,存在白云石化现象,过去对这一现象成因机理的研究较少。为此,综合岩心和镜下薄片观察、主量和微量元素、碳氧同位素定量分析等多种分析测试结果,研究了良里塔格组白云石的岩石学特征和地球化学特征。结果表明:(1)该区白云石具有高Fe、Mn,低Sr、Na,δ~(13)C低正值,δ~(18)O高负值的特征,指示其为埋藏成因模式,与热液作用无关;(2)Ce轻微负异常,Eu中度亏损指示该区白云的形成环境为弱氧化—弱还原;(3)白云石化过程持续时间较长,存在多期白云石;(4)白云石化流体来自于浅埋藏期富Fe、Mn的高盐度地层卤水,以缝合线和溶孔作为运移体系,形成了良里塔格组白云石沿缝合线和溶孔发育的特征。结论认为:由于白云石化过程持续时间长,若白云石交代后周围仍有孔隙空间,则晚期胶结的白云石将围绕早期白云石继续生长直至完全充填孔隙空间,因而白云石化作用对良里塔格组储层主要起到了破坏性作用。
[Abstract]:The Upper Ordovician Litag formation is an important oil and gas reservoir in the central part of Tarim Basin. Its main lithology is limestone and there is dolomitization. Synthesizing core and microscopic thin slice observations, principal and trace elements, quantitative analysis of carbon and oxygen isotopes, and other analytical and testing results, The petrological and geochemical characteristics of dolomite in the Lianglitag formation have been studied. The results show that dolomite in this area has the characteristics of high Fefern, low Srnna, low positive value and high negative value, indicating that the dolomite is a burial genetic model. The moderate depletion of EU indicates that the formation environment of the white clouds in this area is weak oxidation-weak reductive nitrite 3) the dolomitization process lasts a long time. The dolomitization fluid is derived from the brine of high salinity formation rich in Fe and mn in the shallow burial period, and takes suture lines and dissolved pores as the migration system. It is concluded that due to the long duration of dolomitization, if there is still pore space around dolomite after metasomatism, Later cemented dolomite will continue to grow around the early dolomite until the pore space is completely filled, so dolomitization plays a destructive role in the reservoir of the Lianglitag formation.
【作者单位】：北京大学石油与天然气研究中心;北京大学地球与空间科学学院;中国石油塔里木油田公司勘探开发研究院;中国石油学会;
【基金】：国家自然科学基金项目(编号:41572117) 中国地质调查局地质调查项目(编号:DD20160175-1-1) 中国石油塔里木油田公司科研项目(编号:041014120099)
【分类号】：P618.13

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