近钻头测斜器最优八位置标定法

Optimal 8-position calibration for at-bit inclinometer

近钻头测斜器(ABI)用于石油钻井中随钻测量实际井眼轨迹,是实现钻井设备自动化和智能化的重要部件。但由于其现场标定条件限制,只能用定制双轴转台进行标定,不适合采用常规的十二位置翻滚标定法,故在分析标定原理的基础上,针对现场标定条件提出了近钻头测斜器最优八位置标定法,并定义了该方法最小二乘估计的信息矩阵,而后通过数值计算对其行列式进行优化设计,求出使其行列式最大的位置参数,确定了其最优值。通过标定实验算出近钻头测斜器最优八位置标定法得到的标定参数,并将其与常规十二位置标定法的结果进行对比,验证了该方法的精度,标度因数和零偏的相对误差在10-5量级以下,而失准角误差也在2″以内,完全能够满足实际应用需要。

At-Bit Inclinometer（ABI） is used to measure the real well trajectory while drilling, and it is important component for realizing the automation and intelligentization of drilling device. Due to the field calibration condition, ABI can only be calibrated with customized two-axis turntable, which is not suitable for traditional 12-position calibration. So, according to the field calibration condition, an optimal 8-position calibration for ABI was introduced based on the analysis of calibration principle. The information matrix of least square estimation for this method was defined, its determinant was optimized with numerical calculation, and the optimal position parameter which maximizes the determinant was found. The calibration parameters obtained by the optimal 8-position calibration for ABI with calibration experiment was compared with that obtained by traditional 12-position calibration, and the precision of this method was verified by the comparison. The results show that the relative errors of the scale factors and zero deviations between the two methods are less than 10^-5, and that the errors of misalignment angles between the two methods are less than 2＂, which can fully satisfy the requirements of practical applications.