鄂尔多斯盆地华池地区X96井长7烃源岩地球化学特征及其对致密油成藏的意义

为深化致密油成藏机理，优选湖盆中部华池地区X96井展开全取芯的有机碳、热解、饱和烃色谱色质、干酪根镜检等分析及排烃、成藏等综合地质研究。重点利用这些分析测试资料对X96井长7烃源岩地球化学特征展开详细评价并探讨优质烃源岩在致密油成藏中的作用。X96井长7烃源岩包括油页岩、泥岩与粉砂质泥岩等3种类型，其中油页岩的有机质丰度高(平均15.8%)，有机质组分以无定形体为主，有机质类型好(Ⅰ型为主)，并处于生油高峰阶段，属于优质烃源岩。优质烃源岩生烃量大，强大的体积膨胀作用为其提供了充足的排烃动力，排烃作用较强，造成油页岩相对较低的残留沥青“A”转化率、饱和烃/芳烃值与产率指数，排烃效率超过70%。区域上，油页岩稳定分布于长7底部，上覆大范围致密砂岩，源储直接接触。此类广覆式展布的优质烃源岩大范围、高强度的排烃作用为致密油成藏提供了物质基础与动力来源，对近源致密油的成藏意义重大。

Geochemical Characteristics of Chang-7 Source Rocks from Well X96 in Huachi Area of Ordos Basin and Their Significance on Tight Oil Accumulation

Well X96 from the central lacustrine basin in Huachi area of Ordos Basin was selected to carry out a whole core analysis including organic carbon content, pyrolysis, gas chromatography-mass spectrometry of saturated hydrocarbons, kerogen observed under microscopy, etc., and comprehensive geological research on hydrocarbon expulsion, accumulation, etc., for further study on tight oil mechanism. The detailed evaluation of the geochemical characteristics of Chang-7 source rock and the relationship between high-quality source rock and tight oil accumulation using various analytical data were focused. There are three kinds of source rocks of Chang-7 from Well X96, including oil shale, mudstone and silty mudstone. The oil shale has high content of organic carbon (mean content of 15.8%), its organic matters are mainly amorphous mass with fine organic matter type (mainly type Ⅰ), and it is in the peak stage of hydrocarbon generation, so the oil shale belongs to the high-quality source rock. The high-quality source rock has high quantities of hydrocarbon generating, and the strong action of hydrocarbon generation expanding can provide enough energy for oil primary migration, which can cause strong hydrocarbon expulsion. As a result, the oil shale has low conversion rate of chloroform bitumen “A”, low ration of saturated hydrocarbon to aromatic hydrocarbon, and low yield index, and the hydrocarbon expulsion efficiency can more than 70%. Regionally, the oil shale is stably distributed at the bottom of Chang-7 with large-scale overlaying tight sandstone, the reservoirs contact with the source rocks directly. This kind of widely distributed high-quality source rock with large-scale and strong hydrocarbon expulsion is significant in the near-source tight oil accumulation providing both materials and powers.