Study On Application Of High-Precision Directional Drilling Technology In The CBM

According to the "twelfth-five" plan, exploitation quantity of CBM will reach30billion cubic meter in our country by2015, however, in2010, the exploitatity was only1.5billion cubic meter. This means lots of CBM wells need to be drilled in the next few years. Our country CBM exploration is mainly to adopt the method of a vertical wells before, however, vertical well not only take the low efficiency but high production costs and land area, greatly increasing the cost of CBM. But directional drilling technology for CBM exploration has is of important significance.This dissertation based on a project of2D plexus type of directional drilling for CBM exploration in Baode block, in order to study how to reduce the cost and accident of directional drilling, in the mean time, improve the precision and efficiency. First of all, by contrasting the working principle and field test of cabled inclinometer and wireless inclinometer, we got the conclusion that in shallow directional wells(within1000m), the cabled Inclinometer is more suitable for CBM exploration directional wells for its cost, efficiency and durability. Second, by establishing the mathematical model of the straight-growth-stable wellbore trajectory, can calculate the optimum wellbore trajectory of each directional wells by Matlab software. Finally, by studing the theoretical formula of well track and the theory of well bore trajectory control with the practice, the previous theory formulas can determine the body coordinate of directional wells accurately, but they are not practical on directional drilling. Through space transformation changed the original formula to a set of new formulas that can get the offset of drilling trajectory exactly. These formulas are very suitable for directional drilling. By analysising and improving the relationship of pitch angle and inclination and azimuth angle, the directional adjustment angel is concluded, make the directional control more convenient and accurate. This set of directional control system for2D plexus type directional drilling has got a well validation in the scene. For dozens of directional wells drilling in the last year, no one undershoot, and set a record that finish one well only using32h.