A Fit for Purpose Combination of Positive Displacement Motor and Rotary Steerable Systems Delivers a Step Change in Drilling Optimization in Tomoporo Field: A West Venezuela Case Study

摘要

Drilling directional wells in the Tomoporo field in western Venezuela is a challenging and risky operation. Wellbore instability, differential sticking and weak sand zones are common problems in the area. Considerable Non-Productive Time (NPT) is the result of difficult trips, poor hole quality, circulation losses and stuck pipe incidents. Under these conditions, the use of conventional positive displacement motors (PDM) escalates the risk of stuck pipe when difficult sliding and low rates of penetration increase the exposure to open hole conditions. The use of rotary steerable systems (RSS) allowed mitigating some of the hazards, but high shocks and vibrations (S&V) in laminated formations added to the harsh drilling conditions raised the number of unplanned bit trips and downhole tools damage. A drilling assembly containing a rotary steerable tool below a specially designed, high-torque PDM provided the benefits of both conventional and RSS drilling by delivering faster rotation per minute (RPM) at the bit. The increase in RPM reduced vibration perpetuation and transmission in the rest of the drill string. The PDM dampened S&V, mitigated the effects of stick/slip and helped prevent damage to the RSS tools. The combination of PDM and RSS had a positive impact on the life of the bit and downhole tools, and resulted in an increase in both on-bottom and average rate of penetration. This approach marks a step change in performance, achieving a reduction in drilling time of approximately 50% compared to the average established for the area over the previous 5 years. This paper will present a detailed study of this fit for purpose solution to increase footage per day mitigating shocks and vibrations and its success in dramatically reducing risk in directionally drilled wells.