Distinct Applications of MWD, Weight on Bit, and Torque

Abstract

Recent enhancements to measurement-while-drilling (MWO) tools have increased drilling efficiency in directional wells on the North Slope of Alaska. With information provided by downhole weight on bit (WOB) and torque sensors, more timely and accurate decisions have been made, resulting in lower costs per foot. Specific applications of this technology include bit optimization, directional feedback, and drillstring-friction analysis. This paper discusses actual cases where the use of data from these downhole sensors has improved drilling performance. This information will benefit those interested in optimizing polycrystalline-diamond-compact (POC) and rollercone bit runs, improving directional-drilling assembly predictability and performance, minimizing surface torques, and planning high-departure wells.Theory PDC Bit Optimization. Koskie et al. 's1 procedure for optimizing the POC bit requires measuring the forces on the bit and knowing the formation. The MWO's of downhole WOB and torque measure actual forces on the POC bit. The formation type being drilled is predicted with the dimensionless torque value, T D , the torque per unit weight:

Shallow Kick-off Extended Reach Drilling in GOM

“…The worst cuttings transport occurs between 40 to 45 degrees due to cuttings sliding back down the well bore. The uses of high rotary speeds (120+) are typically used to enhance hole cleaning during off-bottom circulation [5].…”

“…Due to the drilling mechanics associated with steerable systems, small steps are produced in the wellbore when the drilling mode changes between sliding and rotary mode. An additional benefit of the rotating stabilizer on the motor is a smoothing of these steps which reduces the overall tortuosity of the wellbore with resulting torque reduction [5].…”

Improve Drilling Safety and Efficiency With MWD Sensors

“…Downhole WOB (weight-on-bit) and torque differ from surface measurements significantly. The difference is especially pronounced in a deviated hole or when near-bit stabilizers are used in a drill string [5][6][7][8][9]. The difference between surface WOB and MWD measured downhole WOB can be used to determine transfer efficiency.…”

Estimation of Rock Compressive Strength Using Downhole Weight-on-Bit and Drilling Models

“…Real-time wellbore fluid dynamics and wellbore friction factors were shown to identify hole cleaning efficiency, stuck pipe, differential sticking, formation changes and mud lubrication issues (Falconer et al, 1989). Measurements of DWOB, downhole torque and surface weight-on-bit (SWOB) were demonstrated to be effective in assessing and optimizing the performance of a bit, mud motor and bottomhole assembly while drilling through sand/shale sequences or formations which are difficult to steer through (Belaskie et al, 1993). This approach was shown to reduce trial and error based approach, excessive drill bit wear, unnecessary trips and rig time.…”