不同地质条件下页岩气水平井地质导向方法研究

Research of Shale Gas Horizontal Well Geosteering in Different Conditions

南方下古生界海相页岩分布广泛,累积厚度大,其中志留系龙马溪组页岩有机热演化程度适中,分布连续、广泛,是我国页岩气勘探开发的重要目标层系。以川东南彭水—南川地区为例,探讨分析了该地区地质特点以及甜点段选择依据。水平井钻井过程中主要解决三个问题:①利用测、录井资料准确拾取层位,做好层位对比;②利用不同计算方法预测地层倾角;③根据地质特征利用不同方法求取靶点垂深。在确定靶点空间位置后,入靶姿势的选择会在一定程度上影响后续施工难度,文章针对三种主要地质情况提出了不同的入靶策略。该地区的现场应用结果表明,已完钻的28口水平井中,平均水平段长1 540m,优质页岩钻遇率达98.6%,纵向资源利用率在较高水平。结论认为,在充分的地质认识以及物探资料基础上,合理地运用不同地质导向方法可实现水平井准确入靶以及精准穿行。

The lower palaeozoic marine shale in Southern China is widely distributed and has a large cumulative thickness, of which the Longmaxi Formation shale of Silurian strata whose organic heat evolution is moderate, continuous and widespread, is the most potential target in exploration and development. By taking Pengshui-Nanchuan work area in Southeastern Sichuan Basin as an example, this paper explores and analyzes the geologic characteristic of this area and how to select target layer. There are three key issues that should be done during the geosteering of horizontal wells. （1） using logging data to accurately pick upthe horizon and making a good contrast of the horizon; （2）calculating apparent formation dip with different methods;（3）getting target＇s vertical depth by different methods in different conditions. After determining the target position, the selection of target position will affect the difficulty of subsequent construction to a certain extent. In this paper, different strate- gies for target entry are put forward in view of the three main geological conditions. Field application results in this area show that the average horizontal section of the 28 drilled wells is 1 540 meters long and the drilling ratio of high quality shale reaches up to 98.6 % the level of resource utilization is high in vertical dimension. It can be concluded that it is possible to apply different geological guidance methods to accurately target and pass through horizontal wells on the basis of ploration data. full geological understanding and geophysical exploration data.