| 靖边潜台奥陶系马五4亚段白云化作用研究 |
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| 引用本文： | 胡光明,罗顺社,倪,超,肖红平.靖边潜台奥陶系马五4亚段白云化作用研究[J].沉积学报,2014,32(1):110-117. |
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| 作者姓名： | 胡光明 罗顺社 倪 超 肖红平 |
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| 摘 要： | 从靖边潜台奥陶系马五段主要岩石类型出发，综合分析沉积特征和地球化学特征，认为靖边潜台奥陶系存在三种白云化作用:（1）泥粉晶云岩与硬石膏共生，形成于盐度较高的局限蒸发潮坪，为准同生白云化所形成；（2）粗粉晶云岩分布较局限，夹于与硬石膏共生的泥粉晶云岩层之间，不与硬石膏共生，但低有序度和略富钙的特征表明其为回流渗透白云化成因；（3）岩溶风化壳较发育区的孔洞缝中大量次生方解石的残余组构表明，去白云化之前的白云石以细砂晶为主，多为自形、半自形菱面体，部分具有环带构造和“亮边雾心”，形成温度为52.30℃~78.05℃，碳氧同位素特征与典型的埋藏白云石较接近，说明其为浅-中埋藏环境下形成的白云石。这三种白云化作用中，准同生白云化是最主要最普遍的白云化类型，其次是浅-中埋藏白云石，回流渗透白云化分布较局限。明确马五4亚段的白云化类型，对于重建岩相古地理、研究储层的形成机理、提高勘探的成功率有重要意义。
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| 关 键 词： | 准同生白云化 回流渗透白云化 埋藏白云化 靖边潜台 马五4亚段 |
Dolomitization Research of Ordovician Majiagou 54 Sub-member,Jingbian Platform |
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| Abstract: | In Jingbian platform, Ordovician Majiagou 5 member is an important natural gas reservoir in Changqing oilfield. But there exists a long argument about its dolomitization type. This issue has been discussed on the basis of Majiagou 54 sub-member. In this paper, after researching the sedimentary and geochemical characteristics of different rock types, the authors draw a conclusion that penecontemporaneous, reflux and burial dolomitization are main dolomitization types in this region. (1) Micritic and silt-sized crystal dolomite which is always associated with anhydrite, deposited in restricted and evaporative tidal flat with high salinity, and formed by penecontemporaneous dolomitization. (2) Coarser silt-sized crystal dolomite is distributed among the layers of micritic and silt-sized crystal dolomite with anhydrite, and its coarser crystal grain, lower degree of order and slightly richer calcium show that this type dolomite is formed by reflux dolomitization. (3) Much secondary calcite is spread in karst layer, and the metasomasis residual texture shows that the grain size of the dolomite before dedolomitization is mainly fine crystal, partially with euhedral-subhedral texture, zonal structure, and bright border with vague center. Their inclusion temperature span is from 52.30 ℃ to 78.05℃, and the characteristics of carbon and oxygen isotopes are more similar to typical burial dolomites. All these indicate that the dolomite before dedolomitization is formed in shallow and middle-depth burial diagenetic environment. Clarifying the dolomitization type of Majiagou 54 sub-member is very important to rebuild lithofacies palaeogeographic, research the reservoir formation mechanism, and improve the success possibility of exploration. |
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