一种基于旋转调制的高精度近钻头井眼轨迹随钻测量方法研究

Wellbore trajectory surveying is one of the critical technologies in the oil prospecting and geological exploration. Since the measurements are precise, independent, and unrestricted from the magnetic interference, inertial measurement technology has become one of the developing directions for the advanced surveying techniques. Fiber optic gyroscopes (FOG) which is the core component in the inertial measurement unit (IMU) have the potential to be an ideal candidate both for the near-bit measurement while drilling (MWD) and for the cased well survey. Based on our previous studies on inertial measurement technologies and fiber optic gyroscopes, we propose the exploration of methods and theories for high quality measuring of wellbore trajectory using FOG-based IMU. To meet the application environment challenges in reality for directional drilling, on the one hand, due to the influence from the wide temperature range, strong shocks and vibrations in the harsh application environment, many errors generate in the sensor measurements as well as in the system measurements. After carefully analyzing the error mechanisms, modeling and compensation techniques are implemented in order to address the environmental adaptability problems of FOG-based IMU. On the other hand, effective external information which is to be integrated with the navigation algorithm is systematically examined and developed, thus the accumulated errors of the inertial system in extended surveys can be well eliminated. The proposed content and methodology in this research is innovative. It is the expansion of our studies on inertial drilling measurement theory over the years. The results of this research can be used in drilling measurement, geological survey and other fields. This research have urgent requrements in MWD and broad perspectives in applications.

高精度井眼轨迹随钻测量是石油和地质勘探的关键技术之一。惯性测量因其精度高、自主性强、不受地磁干扰等优势成为高精度井眼轨迹测量的新方向。随着技术的发展，光纤陀螺成为近钻头随钻测量和套管井轨迹复测的理想选择。课题结合本单位在惯性测井和光纤陀螺的研究基础和优势，提出一种基于光纤陀螺的高精度井眼轨迹近钻头惯性测量方法，并针对定向钻井应用中的科学问题，一方面，从随钻测量应用中空间狭小、温度变化范围大、冲击振动强等恶略环境引起的惯性器件的误差机理进行分析建模与补偿研究，解决光纤陀螺器件在随钻测量中的环境适应性难题；另一方面，通过近钻头钻具的旋转调制，探索通过特有的外部信息提高长时间惯性测量精度的新方法，解决惯性测井误差随时间积累的难题。该课题研究是课题组多年来惯性测井理论研究积累的进一步深化。研究成果在定向钻井随钻测量、金属套管井定位、地质勘探等领域具有迫切的需求和广泛的应用。

针对目前光纤陀螺在随钻测量应用中面临空间狭小、温度变化大、振动冲击大、工作时间长等因素，进行了基于旋转调制的高精度近钻头油井轨迹测量方法的研究。主要内容包括3个方面：.（1）结合钻具组合的一体化光纤陀螺温度梯度误差机理及补偿方法研究.（2）基于钻具旋转“调制”的高精度惯性组合测量误差机理及补偿方法.（3）基于光纤陀螺的高精度近钻头随钻测量实验验证研究.通过以上理论分析和和实验研究，取得如下的研究成果：.（1）建立了一体化小型三轴光纤陀螺温度模型，揭示了井下环境大范围温度梯度造成的光纤陀螺的误差漂移机理，为光纤陀螺温度补偿方法提供了依据。.（2）结合随钻测量钻具“旋转调制”、“零速修正”、“轨迹井深”及“钻进速度”多种外部有效信息，进行了惯性为主的组合导航算法研究，解决了随钻测量中惯性器件随机常值漂移导致的长时间连续测量定位误差随工作时间积累的难题。.（3）对组合导航方法、惯性+磁性组合定位方法进行了实验室内的仿真研究，在此基础上，对油井轨迹惯性测量进行了温度特性和转台的实验研究，验证了所提理论方法的正确性，为进一步的工程应用提供了依据。