崖南凹陷Y1井崖三段煤系烃源岩发育规律

Development Regularities of the Coal-measure Source Rock in Ya-3 Member of Yacheng Formation,Well Y1,in Yanan Depression within Qiongdongnan Basin

基于Y1井煤系烃源岩样品微量元素分析、 煤岩显微组分及热解测试结果, 结合小波分析的米氏旋回划分结果, 系统研究了崖南凹陷Y1井崖三段煤系烃源岩特征及发育规律.研究表明①以104和260尺度结合岩芯沉积序 列及地球化学测试结果, 将崖三段划分为2 个中期和5 个短期米氏旋回, 垂向上表现为旋回厚度及烃源岩比例向上增 大的趋势, 中期旋回上部为烃源岩优势发育层位, 其中 IA2、 IA3和 IB2为煤系烃源岩发育的优势旋回;②煤系烃源 岩有机显微组分表现为富镜质组、 贫惰质组、 贫壳质组＋腐泥组, 镜质组含量为44%-100%, 平 均 为 83%, 以基质镜质 体及镜屑体为主, 烃源岩类型以Ⅲ型（ 腐殖型） 有机质为主, 少量为Ⅱ2型（ 腐泥-腐殖型） 有机质, 烃源岩以产气为主, 其成熟度较低, R值平均为1.12%, 处于生烃阶段初期;③煤系烃源岩发育受多种因素控制, 其中断陷盆地向坳陷 盆地的转化时期是成煤的关键构造时期、 强烈进积作用使得煤系烃源岩保存不全、 区域海平面上升时期是成煤的关 键时期、 短期旋回小波曲线右偏拐点处为煤系烃源岩相对发育层位.

Based on the analysis of trace element, maceral and the results of rock pyrolysis of the coal-measure source rock samples from Well Y1, the development regularities of the coal-measure source rock in Ya-3 member of Yanan depression were systematically studied combining the Milankovitch cycle division results of wavelet analysis. This re-search shows that： （1）Based on the 104 and 260 wavelet scale of Milankovitch cycling, combined with the sequence of core and geological test results , two medium cycles and five short-cycles were identified in Ya-3 member, which points out that the coal-measure source rock tends to thicken visibly in vertical direction, and the proportion of the source rock increases clearly upward in each cycle and it is mainly developed on the top of the medium cycle, in which I A2, I A3 and I B2 are the dominant cycles ; （2）As for organic macerals, the source rock is vitrinite-rich, inetinite-poor , exinite-poor and sapropelinite-poor. Of all the organic macerals, the average concentration of vitrinite is 83%, which accounts for 44% ？100% of the total content. The vitriniteis mainly composed by desmocollinite and vitrodetrinite, and the kerogen types of the source rock are primarily Type III （ humus type） and some Type II （ sa-propelic-humus type） organic matter. Besides, the source rock generates gas prevailingly, and it is in the initial stage of hydrocarbon generation with low maturity. The average value of Rois is 1.12; （3） The development of the source rock in the study area is controlled by multiple factors, and the period in which the faulted depression basin trans-formed into a sag basin is a critical tectonic stage of coal formation. The incomplete preservation of the source rock re-sulted from the process of strong progradation, and the time in which regional sea level rising was also a critical period of coal formation, and the toward-right inflection point of the short-cycle represented layer which was relatively rich in coal-measure source rock.