Deviation Analysis and Correction of Direction Control for Horizontal Directional Drilling Crossing

Crossing by Horizontal Directional Drilling (HDD), characterized by short construction period, high quality and little impact on environment, is widely used in pipeline crossing engineering. Deviation between the practical and theoretical exit point, where the bit unthreads, is difficult to control. Excessive deviation could not only cause unconformity of requirement, but also expand the correction and make re-drilling more difficult. In sum, accurate controlling of the drilling direction is the key to the success of the crossing. Fortunately, wired directional control system is fit for the crossing of deep and long pipelines for large or middle scale directional drill rigs due to its high precision. Based on the working principle of the system, possible reasons causing deviation are analyzed, some methods for deviation correction are proposed, and the operation for lateral deviation controlling in a practical construction is studied. The results indicate that, there are many factors that can lead to the deviation, such as the precision of a directional apparatus, theoretical error of the directional crossing, the error of measurement and interference sources on the ground or underground. However, according to the practical situation, the deviation could be confined in a required range as the construction required through the combination of tru-tracker system and some proper control measures.