摘要：It is necessary to pay attention to the anti-collision between the active well and the drilled offset well in the directional drilling operation,especially in the block with dense well pattern.The key to the anti-collision technology lies in the accuracy of well trajectory measurement.Due to the inevitable measuring error,there is uncertainty in the well trajectory.For instance,the wellbore may be anywhere in a circle with a diameter of 30m or larger at the depth of 3000m.It includes measured depth,inclination and azimuth in the well trajectory measurement parameters.Generally,there are two sets of measurement parameters using different measuring tools at different stages (MWD is used in drilling operation,and multi-point re-measurement after total depth) to measure the parameters for the drilled well,with both measurements having errors whose partial errors are random.Therefore,it is not completely consistent for the two well trajectories calculated separately by the two sets of measurement parameters,nor does the uncertainty of well trajectory occurred by measuring errors.However,the final input well trajectory is only calculated by one set of measurement parameters,and the redundant measurements are not fully utilized to obtain the most reliable well trajectory and to assess its uncertainty.This paper forms a function expression of optimal well trajectory position coordinates,measurement parameters and corrections for the drilled wells on the basis of surveying adjustment theory.Linearize the function expression while meeting accuracy to obtain the optimal estimation of well trajectory position coordinates through least squares method,and calculate the covariance matrix of uncertainty of well trajectory.The new method obtains the most probable well trajectory and the uncertainty range,which can provide decision support for safe drilling in the field.
