A Customised Solution Using Catenary Coiled Tubing to Deploy a Gas Lift Valve Deepening System With Straddle Packers For a Challenging Horizontal Well Offshore Brunei

Abstract

An offshore horizontal oil well was identified as having multiple tubing leaks and depleting reservoir pressure. Intervention was required to reinstate the well and optimize the gas lift system performance to maximize oil recovery. Various challenges were identified in the project design stage due to the horizontal well trajectory and its potential to cause debris obstructions combined with the absence of any capability to monitor downhole parameters. Software simulations were performed to determine the downhole reach limitations of the rigid tool string to ensure that the deepest Gas Lift Valve (GLV) could be successfully deployed to the target depth under live well conditions. The viability of safely deploying such a long Bottom Hole Assembly (BHA) from a limited deck space with a short riser height also needed to be resolved. To accomplish this while maintaining a double barrier on a live well without setting a deep plug and killing the well required detailed planning. A specific space out of the Coiled Tubing (CT) Pressure Control Equipment (PCE) was tailored to enable the simultaneous holding of a 350 meters long gas lift string while also allowing make-up of the packer assembly on surface. Due to the completion design not containing a suitable profile for depth reference with a conventional mechanical locator tool, the Real-Time (RT) catenary CT system was selected as an ideal method of achieving reliable depth correlation. The catenary CT system, equipped with a BHA containing various RT sensors such as pressure, temperature, compression, tension, inclination, Casing Collar Locator (CCL), Gamma-Ray (GR), and torque, was critical in monitoring the downhole parameters in this challenging trajectory to allow decision making and confirmation during the packer setting process. Despite the complexity of job design, preparation, and operational planning with challenges involving pumping, flowback, and the CT package set up in an offshore environment, this customized solution successfully deployed 350 meters of GLV deepening string with precisely set straddle packers to isolate the leak points without any issues. The completion of this project successfully reinstated significant production following a prolonged shut-in period, and gas lift performance was optimized for maximum oil recovery from the considerable remaining oil reserves in the reservoir. This project marked the first successful deployment of a thru-tubing GLV deepening system on a horizontal well for the asset operator. The catenary CT system was an effective solution that managed to safely achieve all of the objectives while overcoming all the challenges faced throughout the project.