Technical Analysis of Horizontal Section Geosteering

The angle between borehole trajectory and formation interface is the key parameter of horizontal section trajectory control in the geosteering process of horizontal wells. In order to reduce the probability of drilling out the reservoir in horizontal section, a new method is proposed to calculate the angle between trajectory and formation boundary in horizontal section under different drilling formation polarity types. The mathematical formulas that included the formation attitude of horizontal well, the bit lie in the target formation position, the drilling formation polarity type of the trajectory, the relative angle between the bed boundary and trajectory are put forward. According to the drilling reservoir scenario of the horizontal trajectory and the principle of trajectory adjustment, the reasonable relative angle and the trajectory design during trajectory control based on the drilling formation polarity type are determined to improve the net to gross rate of high-quality reservoirs. The practical application shows that this method can judge the inclination angle deviated from the formation boundary in advance, which provides a quick method for the adjustment of the horizontal section trajectory. The research results provide a intuitive and quantitative method for pre-drilling trajectory design of horizontal section, trajectory warning and adjustment in geosteering.