The method of selecting layer chasing or sidetracking after the horizontal section of the coalbed methane horizontal well breaks out

Abstract

The invention discloses a method for selecting a chasing layer or sidetrack drilling after a layer of a horizontal section of a coal-bed methane horizontal well is out. The method particularly comprises the steps of calculating the required time T1 of the chasing layer: T1=10*(alpha+beta)*T2 / b+5*sin1degree*(alpha2+alpha*b)*T3 / (b*sinbeta)+10*(alpha+beta)*T4 / (b+h)+5*sin1degree*(alpha2+alpha*b)*T4 / (b*h*sinbeta), wherein T2 is the average drilling time for directional drilling; T3 is the average drilling time of a complex chasing layer section; T4 is the average time for connecting single drill pipe and surveying each time; alpha is an angle difference of the out layer; beta is a reverse angle difference of the chasing layer after the layer is out; b is the maximum changing rate of well slope permitted in the horizontal section of the coal seam per 10 m; h is the length of the single drill pipe; 2) T5, the time required for sidetrack drilling, is calculated according to the sidetrack drilling process and drilling tools: If T1 < T5, the chasing layer is selected; if not, the sidetrack drilling is selected. The method uses the formula to calculate the estimated chasing layer period, and compares the chasing layer period with the required time for sidetrack drilling, and then the next construction scheme is selected reasonably.

Description

technical field [0001] The invention belongs to the field of coal-bed methane development, and in particular relates to a method for selectively chasing layers or sidetracking after the horizontal section of a coal-bed methane horizontal well exits the layer. Background technique [0002] At present, during the drilling operation of coalbed methane horizontal wells, the relationship between the drill bit and the coal seam is generally judged based on the upper gamma and lower gamma difference (EM-MWD) or the deep-shallow resistivity difference (LWD) measured by the instrument while drilling. The wellbore trajectory can be adjusted according to data such as inclination and azimuth, so that the wellbore trajectory can accurately track the coal seam. However, there are generally large blind spots in instrument measurement. In addition, factors such as lack of adjacent well data, lack of seismic data accuracy, and complex and changeable geological structures make it impossible t...

AI Technical Summary

Problems solved by technology

However, there are generally large blind spots in instrument measurement. In addition, factors such as lack of adjacent well data, lack of seismic data accuracy, and complex and changeable geological structures make it impossible to ensure that the trajectory always passes through the coal seam during construction. The dilemma of returning to a certain position and re-tracking

[0003] In the construction of the horizontal section, once the layer is out, whether it is directly chasing the layer or directly sidetracking, it may increase the drilling cycle due to improper selection, waste drilling costs, reduce the coal seam drilling rate, and even cause drilling failure due to blind layer chasing. Risks, currently in the construction process are mostly judged by human experience, lack of reproducibility

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