Research On Trajectory Calculation Method In Motion Correction Of Nuclear Magnetic Resonance Logging While Drilling

Nuclear magnetic resonance logging while drilling while overcoming the limitations of wireline logging application and mud intrusion in some special situations,it can measure the original formation information in real time,guide the drill bit to drill in the production zone,improve productivity and recovery rate,and reduce drilling costs.Affected by the movement of the drilling tool and the collision with the formation,the instrument is in random motion,which causes the amplitude of the echo signal to decay.The predecessors based on a large amount of logging data,summarized and analyzed the correction formula for the axial and radial motion of the nuclear magnetic resonance logging while drilling,but this correction method requires accurate axial motion speed and radial displacement trajectory for the tool measuring.This paper discusses and analyzes the calculation method of the instrument trajectory.First,it analyzes the force and movement of the drill collar downhole.Based on the principle of nuclear magnetic logging,it explains the effect of movement on the quality of nuclear magnetic logging while drilling,and clarifies the necessity of accelerometer measurement of drilling nuclear magnetic resonance logging instrument and the difficulty of accelerating instrument measurement are analyzed.Then,for the difficulty of acceleration measurement,a method for measuring the acceleration of the instrument is proposed,and the calculation method of the instrument's trajectory and posture is derived.Finally,the given instrument's trajectory and acceleration are simulated and the acceleration measurement method and the trajectory calculation are verified the feasibility of the method.