Maximizing lateral length while minimizing costs associated with a new wellbore has been a goal of the industry for many years. The trend in horizontal drilling is to have progressively longer laterals within the pay interval. This paper will address one of the major issues associated with extended reach laterals (ERL): the ability to overcome wellbore obstacles and install casing to measured depth (MD) of the wellbore. This paper describes a method for installing openhole multistage (OHMS) tools that has been developed and run successfully in the DJ Basin in Colorado for ERL wells.
During a typical OHMS installation, the tool string is filled with fluid as it is run into the wellbore. The drilling rig then slides the tool string through the horizontal section with a combination of hydraulic force and fluid weight. If the rig cannot overcome friction forces caused by the drag of the tool string along the bottom of the wellbore, then the tool string will not reach the desired depth and/or become stuck. To reduce these friction forces, a glass barrier burst disk sub is installed above the liner hanger packer (LHP) preventing fluid flow below the LHP. As the tool string is lowered into the wellbore, the section below the LHP now "floats" to the desired depth because of the trapped air. By changing the buoyancy of the tool string, the drag friction is greatly reduced. Reducing the drag friction during liner installation requires less weight to install the liner. Using this method, the lateral length of ERLs using OHMS systems can be greatly increased. The drill pipe (DP) above the burst disk is filled with fluid, providing fluid weight. When the tool string reaches the desired depth, internal pressure is applied to the tool string breaking the glass burst disk barrier and allowing for communication with the rest of the tool string.
For this case study, the burst disk sub functioned properly in all eight runs. All wells saw an increase in hook load at MD of approximately 45,000 lbs. This means there was an additional 45,000 lbs of force present to get the tool string to MD. As mentioned, the burst disk did limit the ability to circulate fluid, but did not introduce any additional expenses. The performance of the burst disk matched simulated torque and drag (T&D) model installs and allowed for less hydraulic force to be used. This led to increasing well design efficiency.