Advanced Integration of Coiled Tubing Optical Telemetry, Multilateral Tools, and Retarded Acid Systems in a Level Four Six-Legged Multi-Lateral Oil Producer - A Comprehensive Case Study from North Kuwait Field

Abstract Horizontal drilling technologies have evolved during last decades making possible wells with thousands of feet of long horizontal sections. These drilling advancements have contributed to drill more intricate multilaterals wells to ensure a thorough contact with the reservoir. In terms of well accessibility for rig-based well interventions, these complex completion configurations add significant challenges. Upon drilling is completed, coiled tubing (CT) matrix acid stimulation is one of the first interventions used to remediate the formation damage and bring the well back on production. Operator in Kuwait drilled a level four six-legged multilateral well in the north area to maximize reservoir contact within lower and upper Tuba carbonate formations. This drilling approach enables several production schemes and versatility in the pursuit of economical production. As such, this completion approach required an advanced intervention technique that relied on CT optical telemetry and multilateral entry tool (MLT). Real-time downhole readings included casing collar locator (CCL), gamma ray, CT internal pressure, annulus pressure, annulus temperature, and axial force for accurate depth control, rapid lateral identification, optimal MLT actuation and understanding of dynamic downhole conditions along the operation. The level-four multilateral candidate had a six 6 1/8-in. uncased horizontal sections that needed cleanout from drilling oil-based mud (OBM) and matrix stimulation using an emulsified retarded acid system (ERAS) for enhanced wormholing into the carbonate rock. The lateral sections exhibited an average of 2,500 ft and the reservoir featured a bottomhole temperature near 130°F and bottomhole pressure close to 2,100 psi. By combining real-time optical telemetry with MLT, the profiling of three laterals was completed in less than 4 hours for each one, optimizing the rig time and the course of the treatment. Prior to the matrix stimulation, three laterals were conditioned via CT through a multifunctional solvent consisting of a synergistic blend of aromatic solvent and surfactants intended to breakdown and disperse OBM residuals without the need of mechanical agitation and also leaving the rock water wet. The three laterals were then acidized in a single run by pumping 450 bbl of multifunctional solvent followed by 1,500 bbl of ERAS. When compared to conventional CT intervention in multilateral wells, this enhanced intervention approach optimized the total intervention time by 33%, being fundamental the ability to make fast-informed decisions from optical telemetry. This paper documents a value case study for CT rig-based intervention in Kuwait, where combination of an array of technologies, such as CT optical telemetry, MLT, multifunctional solvent and ERAS, enabled cleanup and acidizing three laterals from six-legged multilateral wells in a single run. The lessons learned are now the reference for other operators in the Middle East for performing interventions in multilateral wells.