光纤陀螺随钻测斜仪钻进中井眼轨迹测量方法研究

为提高光纤陀螺随钻测斜仪的井眼轨迹的测量精度,采用卡尔曼滤波组合的测量方法,对井斜、方位和工具面失准角进行估计。由于姿态失准角的估计精度与其可观测性密切相关,为了提高估计精度,文章分别在匀速、匀加速和匀速转动三种钻进运动状态下,采用分段线性定常系统(PWCS)和奇异值分解(SVD)的方法分析了姿态失准角的可观测性,并分析了钻进中井斜角和转动速率对姿态失准角估计精度的影响。由仿真结果可知,匀速钻进时,方位失准角不可观测;匀加速钻进时,方位失准角可观测且在水平井中可观测性最强,随着井斜角度增大,方位角、井斜角的测量精度逐渐提高;绕轴向匀速转动钻进时,方位失准角的可观测性和估计精度均优于匀速、匀加速钻进状态;角速率由0°/s增加到5°/s时,三个姿态失准角的估计精度均增大并逐渐趋于稳定。文中提出的轴向转动钻进运动可有效提高井眼轨迹的测量精度。

Measurement Method of Borehole Trajectory In-drilling for FOGs-Based Inclinometer While Drilling

In order to improve the measurement accuracy of borehole trajectory for inclinometer while drilling based on FOGs (FOGs-based IWD), Kalman filter is often used in combination measurement, so the misalignment angles of inclination, azimuth and tool face angle can be estimated. The estimation accuracy of attitude error is closely related to its observability, thus in order to improve the estimation accuracy, the observability in-drilling of attitude misalignment was analyzed by using piecewise linear constant system (PWCS) and singular value decomposition (SVD) under three drilling states of uniform speed, constant acceleration and uniform rotation. Then, the influences of inclination angle and rotation rate on the estimation accuracy of attitude misalignment were analyzed. Simulation results show that the azimuth misalignment angle is unobservable in uniform speed drilling. But the azimuth misalignment angle is observable in the uniform acceleration drilling and the observability is the strongest in the horizontal well. With the increase of inclination, the measurement accuracy of azimuth and inclination is improved. The observability and estimation accuracy of azimuth misalignment angle in rotary drilling are better than that in uniform and constant acceleration drilling. When the angular rate is increased from 0°/s to 5°/s, the estimation accuracy of attitude misalignment angle increases and tends to be stable. The rotation drilling movement proposed in paper can effectively improve the measurement accuracy of borehole trajectory.