Abstract
In the oil industry, the measurement-while-drilling (MWD) systems are usually used to provide the real-time position and orientation of the bottom hole assembly (BHA) during drilling. However, the present MWD systems based on magnetic surveying technology can barely ensure good performance because of magnetic interference phenomena. In this paper, a MWD surveying system based on a fiber optic gyroscope (FOG) was developed to replace the magnetic surveying system. To accommodate the size of the downhole drilling conditions, a new design method is adopted. In order to realize long-term and high position precision and orientation surveying, an integrated surveying algorithm is proposed based on inertial navigation system (INS) and drilling features. In addition, the FOG-based MWD error model is built and the drilling features are analyzed. The state-space system model and the observation updates model of the Kalman filter are built. To validate the availability and utility of the algorithm, the semi-physical simulation is conducted under laboratory conditions. The results comparison with the traditional algorithms show that the errors were suppressed and the measurement precision of the proposed algorithm is better than the traditional ones. In addition, the proposed method uses a lot less time than the zero velocity update (ZUPT) method.
Highlights
In the oil industry, borehole trajectories needs to be measured accurately in drilling engineering and geological work [1,2]
The main motivation of this paper is to develop a fiber optic gyroscope (FOG)-based MWD
The balance tangent method (BTM) assumes that the measuring section is a line which is composed of half of the length of the two measuring section, and the direction of the well is consistent with the direction of the upper and lower measuring points
Summary
Borehole trajectories needs to be measured accurately in drilling engineering and geological work [1,2]. Fiber optic gyroscopes have many advantages over MEMS gyroscopes, such as shock and vibration force resistance, immunity from magnetic interference, and high reliability These advantages make FOG-based inertial measurement units (IMUs) perfect candidates for MWD surveying systems, and this has attracted much interest [6,7,13]. For long-term and high accuracy surveying of FOG-based MWD, the zero velocity update (ZUPT) method is adopted [14]. As an alternative to ZUPT, the in-drilling alignment (IDA) method has been previously proposed and theoretically demonstrated as an approach for limiting the error growth [9,16]. To suppress the INS error growth, a long-term surveying method is proposed based on the drilling feature. The semi-physics simulation is conducted to verify the proposed method based on the FOG-based MWD prototype
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