Successful Intervention into a Six-Leg Multi-Lateral Well Using an Electrical MultiLateral Tool Deployed on Real-Time Hybrid Coiled Tubing for Acid Stimulation of a Kuwait Field - A Case Study

Abstract

Multilateral technology offers multiple benefits to oil and gas operators, including lowering the field development cost by minimizing wellsite construction work and increasing reservoir contact leading to enhanced reservoir production. To gain full advantage of these complex wells, they must be stimulated properly. The operator in Kuwait drilled, cased, and cemented a six-leg, level IV multilateral well targeting two different formations, the upper and lower Tuba. This provided various production options and the flexibility of taking production from either the lower or upper laterals or even all six laterals to help mitigate the risks of drilling horizontal or directional wells. As such, multilateral technology can positively transform the economic viability of reserves in marginal fields. Exploiting the advantages of multilateral technology requires a multi-disciplinary approach to select appropriate well structure, completion design, re-entry flexibility, and production longevity. Intervention in this level IV multilateral well presented several challenges, such as Oil Based Mud (OBM) in all the laterals, encountering a fault in one of the laterals while drilling, and high shale content that can lead to stuck Coiled Tubing (CT) and the loss of fluid returns. Real-time hybrid cable CT was chosen along with an electric multilateral tool to mitigate the various risks involved. This solution includes a hybrid fiber optic and electrical cable installed in the CT string and a modular Bottom Hole Assembly (BHA) equipped with various sensors. An electrically controlled indexing tool, inclination sensor, tool- face sensor, downhole camera, hydraulic knuckle joint, and pulsating stimulation tool were used as part of the BHA to enable real-time diagnostics and dynamic controls from the surface to successfully enter and stimulate all the lateral legs. This configuration helped identify each different lateral without the need to tag the bottom of each lateral. The paper focuses on applications, strategies, and benefits of specific tool configurations developed for multilateral well intervention, enabling the stimulation of all the lower Tuba laterals. This was a particularly challenging operation due to shale in one of the laterals causing several instances of stuck CT with the possibility of a collapsed hole mitigated by using the real-time camera in the BHA. This paper includes strategies that address proper tool selection, confirmation of lateral entry, hydrostatic pressure balance, borehole stability, and acid design. It also explores the potential of new, synergistic strategies and work processes planned for stimulation of the upper Tuba field.