基于动态时间规整算法的方位伽马导向穿层识别方法

Formation-Penetration Identification Method in Azimuthal Gamma Geosteering Based on Dynamic Time Warping Algorithm

  • 摘要: 方位伽马测量具有测量方式灵活、解释复杂度低等优势,广泛用于地质导向钻井决策,但尚未实现方位伽马随钻自动解释。针对该问题,采用动态时间规整算法,识别导向过程中轨迹方向和靶层存在相对夹角情况下的轨迹穿层特征,并引入分段线性逼近和皮尔森系数等方法改进动态时间规整算法,解决了传统动态时间规整算法计算量和奇异点影响程度大的问题;利用上、下伽马和左、右伽马分别指导井斜和方位的导向决策调整,并进行了实例分析。结果表明,改进后算法的计算复杂度大幅下降,运行速度满足随钻过程中实时导向分析需求;相比人工识别精度更高,不仅可以识别导向轨迹在靠近层界面时的穿层特征,还可以对不易分辨的层间特征进行准确识别,有助于改善因伽马测量探测深度浅而被动导向的情况。应用该方法可将超薄层、窄河道等复杂油气藏导向钻井储层钻遇率提升至90%以上。基于动态时间规整的方位伽马导向穿层识别方法改变了依赖人工经验的传统分析模式,为随钻智能化应用提供了新的技术途径。

     

    Abstract: Azimuthal gamma measurement has the advantages of flexible implementation and low interpretation complexity and is widely used in geosteering drilling decision-making. However, the automatic interpretation of azimuthal gamma while drilling has not yet been achieved. Therefore, the dynamic time warping algorithm was adopted to identify the trajectory formation penetration characteristics when there is a relative angle between the trajectory direction and the target layer during the geosteering process. Methods such as piecewise linear approximation and Pearson correlation coefficient were introduced to solve the problems of high computational complexity and singular points in the algorithm. The up and down gamma and left and right gamma were utilized to guide the geosteering decision adjustments for well inclination and azimuth, respectively, and case analyses were conducted. The results indicate that the computational complexity of the improved algorithm is significantly reduced, and the running speed meets the real-time geosteering analysis requirements while drilling. Compared with manual identification, it has higher accuracy. It can not only identify the formation penetration characteristics when the geosteering trajectory approaches the layer interface but also accurately identify the interlayer characteristics that are difficult to distinguish, which helps to improve the passive geosteering situation caused by the shallow detection depth of gamma measurement. The application of this method can increase the drilling encounter rate of geosteering in complex oil and gas reservoirs such as ultra-thin layers and narrow fluvial channels to over 90%. The formation-penetration identification method in azimuthal gamma geosteering based on dynamic time warping algorithm changes the conventional analysis mode relying on manual experience, providing a new technical approach for intelligent application while drilling.

     

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