Enhancing Rigless Intervention Efficiency in Bi-Lateral Oil Producer Through Coiled Tubing Optical Telemetry, Multilateral Tool, and Single-Phase Retarded Inorganic Acid: A Case Study from South Kuwait

Abstract

Developments in horizontal drilling and completion techniques have enabled drilling an increasing number of wells. In the pursuit of cost optimization and enhanced recovery through maximized reservoir contact, operators are placing special interest on multilateral completions. However, multilateral wells add complexity to rigless intervention and production enhancement work as those activities are heavily dependent on lateral accessibility. An advanced rigless intervention in a multilateral well relied on coiled tubing (CT) equipped with optical fiber and real-time downhole measurements and a multilateral entry tool (MLT). Downhole readings included casing collar locator (CCL), gamma ray, CT internal pressure, annulus pressure, annulus temperature, and axial force. Optical telemetry was used for lateral identification and for optimal actuation of the orienting and bent sub-components of the MLT while profiling and accessing the lateral. Throughout the stimulation treatment, optical telemetry was instrumental to understanding changing downhole conditions and keeping injection rates below fracturing pressure. The candidate well was a carbonate bi-lateral oil producer completed through 6 1/8-in. uncased horizontal sections. Both laterals exhibited average length of 2,400 ft, and the reservoir featured a bottomhole temperature near 140°F and bottomhole pressure close to 3,050 psi. Because of real-time optical telemetry, profiling of the lateral was completed in less than 3 hours, which represents 50% reduction of the average profiling time in similar wells. Both laterals were stimulated via CT with a total of 4,000 bbl of single-phase retarded inorganic acid system (SPRIAS), which enables carbonate stimulation with better wormholing performance than emulsified acid while eliminating its drawbacks, such as high CT friction pressure and potential emulsion issues. In comparison with emulsified acid, the pumping time with SPRIAS was 35% lower, bringing additional efficiency to the intervention. The ability to make fast, informed decisions based on optical telemetry was the cornerstone of this intervention approach. This paper documents a value case study for CT rigless intervention in South Kuwait, where the combination of an array of technologies, such as CT optical telemetry, MLT, and SPRIAS, enhanced rigless intervention efficiency, reducing total operation time by 30%, when compared to conventional CT stimulation approach in multilateral wells.