鄂尔多斯盆地奥陶纪盐系地层烃源岩特征及资源远景

 盐系地层所指示的古沉积环境更有利于优质烃源岩的发育.通过对551 块纵向连续碳酸盐岩样品进行热解测试,利用降解率法对有机碳恢复处理,得到可供烃源岩评价的热解数据,结合单井岩相特征综合分析显示:镇钾1 井马家沟组烃源岩整体有机地化指标偏低,部分为中-好级别烃源岩,主要分布于马五段相.马家沟组有机质丰度指标总有机碳(TOC)平均值为0.18%,各组中马二段TOC 平均值最高,为0.28%;TOC 最大值出现在马五段,为1.04%.镇钾1 井有机质类型多数为III型干酪根,但仍发育有一定量的I型和II1型干酪根,分布在马五段和马四段.整体上,马家沟组烃源岩已高过成熟,进入生气为主的演化阶段.泻湖相最有利于发育烃源岩,开阔台地相次之;黑灰色泥晶灰岩-(膏质)准同生灰色云岩-烟灰色岩盐的蒸发旋回中常见相对高的TOC 值.研究表明,烃源岩有机参数纵向变化特征显示马五段最有利于发育烃源岩,是天然气、石盐、钾盐等多种资源蕴藏的有利层位.

Characteristics and Resource Prospection of Hydrocarbon Source Rocks in Ordovician Salt-bearing Strate in Ordos Basin,China

The sedimentary environment of salt-bearing strate is more advantageous than the source rock, and there are many kinds of other minerals. The vertical continuous 551 hydrocarbon source rock continuous geochemical data for Well Zhenjia1 are obtained by the pyrolysis experiments, and by the degradation ratio method after restoring the organic carbon, combined with a comprehensive analysis of the single well facies display, it is shown that the geochemical indicators of Majiagou Formation source rock in Well Zhenjia1 are in overall low,a part of the samples are in normal- good level, mostly in the 5^th Majiagou member. The organic abundance as well as the TOC averaged value are 0.18%, the TOC of the 2^nd Majiagou member is the highest, with the average value of 0.28%, and the 5^th Majiagou member has the highest value of 1.04%. The types of organics in Well Zhenjia1 are mainly type III kerogen, with type I and II kerogen, distributed in the M₄ and M₅ in the source rock in some parts of the well. On the whole, the maturity of the source rock of Majiagou Formation is over-high, and the main production is gas. The lagoon facies is most conducive to the development of hydrocarbon source rocks, and the open platform facies takes the second place. Relatively high TOC value is usually seen in the dark grey micritic limestone-(gypsum) penecontemporaneous gray dolomite-in smoke gray halite evaporation cycle, which is a common phenomena in the 5^th Majiagou member. With respect to the vertical variation characteristics of organic parameters of hydrocarbon source rocks, it is shown that the 5^th Majiagou member is the most favorable strata for development of source rocks, at the same time, this layer is also the most favorable strata for potash and halite deposits. Coupling of multiple potential mineral resources indicate that the 5^th Majiagou member is a favorable metallogenic strata for gas, halite and potash, which provides some hints for future investigations of mineral resources.