Abstract
The methodology described in this paper represented permits to introduce a new open-hole 15K multistage frac (MSF) completion solution in a challenging gas well environment, like high dog-leg severity (DLS) range, washed out boreholes, tight spots and extreme differential pressures between intervals. All started with extensive testing to validate the design, followed by exhaustive job planning, execution, post job and performance review phases.
A novel, slim and compact open-hole (OH) mechanical packer was validated to API 19OH-V1 standards and rigorously tested to additional customer requirements. This packer was part of the OH MSF system, which also includes frac sleeves, a unique V0 metal-to-metal seal expandable liner hanger and upper completion, including 15K V0 PBA validated to API 19 AC and stroked up to 2,000 ft in the presence of gas for validation testing. Multiple offsets well data analysis, torque and drag (T&D) modeling, diverse simulations, evaluation and proper execution of the completion installation assisted in minimizing the operational risks during deployment. This OH MSF system was capable of handling extreme downhole environments, in addition to the 15K acid stimulation cycles and gas production phase.
The 15K OH MSF solution was comprised of one (1) V0 metal-to-metal seal expandable liner hanger, eleven (11) compact and slim OH mechanical packers, two (2) OH anchors, eight (8) ball-activated frac ports, and one (1) hydraulic toe initiation valve. This completion system successfully withstood multiple ream down events to pass various tight spots through the long lateral. The V0 metal-to-metal seal expandable liner hanger was set inside the 7" parent casing. The lower completion was tied back to surface with the upper completion polished bore assembly (PBA). Acid stimulation was performed rigless after the successful deployment of the MSF completion system. The 15K OH MSF completion, despite the severe mechanical constraints suffered during the deployment phase, withstood ultra-high-pressure cycles exceeding more than a 10,000-psi differential pressure in all the eight frac stages. More than 15,000 barrels of fluid treatment with acid were injected through the completion system. The rig and rigless operations demonstrated the high performance and efficiency of the new system to reach target depth, provide zonal isolation in a very tight formation, and performed in acid environment with high-pressure cycles. The new completion system allowed all operational steps to be performed on the well with high operational efficiency.
The slim design and short length of the single element OH mechanical packer enabled the drilling team to reduce the stiffness of the lower completion string. The capability of high anti pre-set resistance to mechanical loads allowed the team to overcome high friction and drag experienced in the extended-reach lateral. The rotational capability of the new OH mechanical packer allowed the completion string to pass through multiple tight spots encountered in the well, and successfully displayed extreme ream-down capabilities. The OH packer exhibited the capability of achieving high-pressure circulation rates. The MSF completion system also demonstrated repeatability of isolation performance during the eight high-pressure acid stimulation stages, overcoming high washouts areas and thereby enhancing stimulation efficiency.
