# A Model-Based Intelligent Adjustment Method of Toolface for Bent-Housing Motor
## 1 Introduction  
In engineering practice, we often need to calculate or predict some parameters in advance, so as to formulate measures early, improve efficiency, and avoid adverse consequences. The toolface adjustment of the bent-housing motor is a typical representative of this kind of situation. At present, the bent-housing motor is still widely used in the construction of directional wells and horizontal wells due to its economy and adaptability to complex well conditions such as high temperature and high pressure [1]. In the process of controlling well trajectory with BHA (bottom hole assembly) containing a bent-housing motor, the orientation of the motor's bending angle needs to be adjusted frequently. The traditional toolface adjustment process is very time-consuming and laborious [2]. Whether the adjustment is in an on-bottom condition or off-bottom condition, the downhole toolface needs a certain response time to reach a stable state after the wellhead drill string rotates at an angle. Once the toolface is stable and recorded by MWD (measure while drilling), it will take several minutes to be uploaded to the drilling platform. If the toolface is not expected,it needs to be readjusted repeatedly until the toolface meets the expectation. Therefore, the traditional toolface adjustment not only increases the abnormal drilling time, but it also relies heavily on the experience of operators. It is very significant to adjust the toolface quickly and accurately to save the drilling cost and improve the drilling efficiency. To some extent, the application of the automation system in drilling has improved the adjustment efficiency of the bent-housing motor toolface. In the directional steering control system proposed by [PERSON] [1; 2], through the joint work of PLC (programmable logic controller), sensor package, HMI (human machine interface), and control package, the toolface of the bent-housing motor can be monitored in real time, and can be adjusted by inputting the rotation angle of the wellhead drill string through HMI, which reduces the labor intensity of manual adjustment and saves the adjustment time of the toolface to a certain extent. In China, [PERSON] [3] also proposed a top-drive-based steering control system for sliding drilling similar to that proposed by [PERSON]. [PERSON] [4; 5] specially carried out the indoor experiment of the asynchronous machine toolface dynamic control system, which verified that the angle accuracy of its driving wellhead drill string rotation is less than 2\({}^{\circ}\), and the drive time is less than 5 s. However, the above-mentioned toolface automation adjustment methods rely on computer-based feedback control, and their effectiveness is largely affected by wellbore friction. Through experiments, [PERSON] [6] found that when there is a large frictional force on the drill string, toolface hysteresis will ensue. When the toolface hysteresis exists, the purpose of rapid and accurate adjustment of the downhole toolface cannot be achieved only by relying on the wellhead automatic drill string torsion system. Without knowing the relationship between the wellhead rotation angle and the change value of the downhole toolface, the toolface still needs to be adjusted repeatedly, and the toolface hysteresis greatly extends the abnormal drilling time. Therefore, the most ideal state is when the downhole toolface can reach a predetermined angle after the wellhead drill string rotates one time. In recent years, some researchers have tried to use dynamics models to describe the relationship between the rotation of the wellhead drill string and the change in the bottom hole toolface. [PERSON] [7; 8] proposed a model-based method for the rapid adjustment and control of the toolface of the bent-housing motor. The simulation example shows that this method can achieve the control goal in a short time, whether for toolface setting off-bottom or correction on-bottom.