A Long-Term Performance Enhancement Method for FOG-Based Measurement While Drilling

Self Cite

The stability of a fiber optic gyroscope (FOG) in measurement while drilling (MWD) could vary with time because of changing temperature, high vibration, and sudden power failure. The dynamic Allan variance (DAVAR) is a sliding version of the Allan variance. It is a practical tool that could represent the non-stationary behavior of the gyroscope signal. Since the normal DAVAR takes too long to deal with long time series, a fast DAVAR algorithm has been developed to accelerate the computation speed. However, both the normal DAVAR algorithm and the fast algorithm become invalid for discontinuous time series. What is worse, the FOG-based MWD underground often keeps working for several days; the gyro data collected aboveground is not only very time-consuming, but also sometimes discontinuous in the timeline. In this article, on the basis of the fast algorithm for DAVAR, we make a further advance in the fast algorithm (improved fast DAVAR) to extend the fast DAVAR to discontinuous time series. The improved fast DAVAR and the normal DAVAR are used to responsively characterize two sets of simulation data. The simulation results show that when the length of the time series is short, the improved fast DAVAR saves 78.93% of calculation time. When the length of the time series is long (6×105 samples), the improved fast DAVAR reduces calculation time by 97.09%. Another set of simulation data with missing data is characterized by the improved fast DAVAR. Its simulation results prove that the improved fast DAVAR could successfully deal with discontinuous data. In the end, a vibration experiment with FOGs-based MWD has been implemented to validate the good performance of the improved fast DAVAR. The results of the experience testify that the improved fast DAVAR not only shortens computation time, but could also analyze discontinuous time series.

Section: Structure Of the Fog-based Mwdmentioning

confidence: 99%

“…Long working hours: the FOGs-based MWD system keeps working underground for more than 200 h. Putting the MWD system down into the well and pulling it up to the ground costs too much time and money [25]. …”

Section: Structure Of the Fog-based Mwdmentioning

confidence: 99%

Application of Fast Dynamic Allan Variance for the Characterization of FOGs-Based Measurement While Drilling

Wang

Zhang

Gao

et al. 2016

Self Cite

“…To weaken magnetic interference from metallic drilling equipment, a magnetometerbased MWD system is typically mounted inside an expensive non-magnetic drill collar [6]. This can effectively remove magnetic interference, due to the metallic materials of the drill collar; however, use of a non-magnetic drill collar imposes the problem of high cost [7]. The removal of magnetic interference via software offers an alternative approach by which to cancel out the magnetic interference that derives from metallic materials and is achieved by characterizing mathematical models of these materials [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

IMU/Magnetometer-Based Azimuth Estimation with Norm Constraint Filtering

Yang,

Zeng,

Xiong

et al. 2024

A typical magnetometer-based measurement-while-drilling (MWD) system determines the azimuth of the bottom hole assembly during the drilling process by employing triaxial accelerometers and magnetometers. The geomagnetic azimuth solution is susceptible to magnetic interference, especially strong magnetic interference and so a rotary norm constraint filtering (RNCF) method for azimuth estimation, designed to support a gyroscope-aided magnetometer-based MWD system, is proposed. First, a new magnetic dynamical system, one whose output is observed by the magnetometers triad, is designed based on the Coriolis equation of the desired geomagnetic vector. Second, given that the norm of the non-interfered geomagnetic vector can be approximated as a constant during a short-term drilling process, a norm constraint procedure is introduced to the Kalman filter. This is achieved by the normalization of the geomagnetic part of the state vector of the dynamical system and is undertaken in order to obtain a precise geomagnetic component. Simulation and actual drilling experiments show that the proposed RNCF method can effectively improve the azimuth measurement precision with 98.5% over the typical geomagnetic solution and 37.1% over the KF in a RMSE sense when being strong magnetic interference environment.

“…Directional drilling refers to the type of drilling where the upper part of the reservoir cannot be accessed on land due to buildings or gravity. Drilling starts from adjacent areas and after a certain amount of drilling, starts on a detour and continues to the desired point using an internal tubing cutter [ 1 ]. In achieving this predetermined goal, a number of parameters need to be measured using various types of Measuring While Drilling (MWD) tools.…”

Section: Introductionmentioning

confidence: 99%

Auto-Calibration and Fault Detection and Isolation of Skewed Redundant Accelerometers in Measurement While Drilling Systems

Moosavi

Moaveni

Moshiri

et al. 2018

The present study designed skewed redundant accelerometers for a Measurement While Drilling (MWD) tool and executed auto-calibration, fault diagnosis and isolation of accelerometers in this tool. The optimal structure includes four accelerometers was selected and designed precisely in accordance with the physical shape of the existing MWD tool. A new four-accelerometer structure was designed, implemented and installed on the current system, replacing the conventional orthogonal structure. Auto-calibration operation of skewed redundant accelerometers and all combinations of three accelerometers have been done. Consequently, biases, scale factors, and misalignment factors of accelerometers have been successfully estimated. By defecting the sensors in the new optimal skewed redundant structure, the fault was detected using the proposed FDI method and the faulty sensor was diagnosed and isolated. The results indicate that the system can continue to operate with at least three correct sensors.