APPARATUS FOR AVOIDING STUCK DRILLING EQUIPMENT AND METHOD OF DETERMINING THE PROBABILITY OF UNSTICKING A STUCK DRILL PIPE

摘要

Apparatus for avoiding stuck drilling equipment during drilling of a well bore over depth intervals where such equipment has stick in similar wells in a geological province includes data storage means for recording a multiplicity of well drilling variable quantities measured substantially simultaneously at a known depth in each of a multiplicity of wells. Such multiplicity of wells includes those in which drilling equipment has stuck and a multiplicity of similar wells where the drill string did not stick. Such data forms the input to multivariate statistical analysis means for calculating for all variables in all wells of each class the maximum separation of said classes from each other. The centroids of all well vectors representing each of the multiplicity of wells in each such classes are then recorded either numerically or by plotting. A currently drilling well relative to said classes is then established by means for calculating its well vector relative to the well classes. Such calculating means sums the products of the coefficient of each variable for the complete group of wells times the current value of each variable in the drilling well. The well vector is then recorded to plot or indicate which variable may be modified within allowable values to change the plotted location of the drilling well toward the centroid or mean of the wells that did not stick the drill string. A method of determining whether a stuck drill string can be freed is provided by calculating the centroids of two groups of stuck wells using the same procedure for multivariate analysis of a multiplicity of drilling parameters to identify whether or not a stuck well is in a group of wells which could not be unstuck.