Feasibility Study of Rigless ESP Deployment in Multizone Wells: A Case Study of Mariann Field, Oriente Basin

Abstract

Electric submersible pumps (ESPs) assist most of the wells in the Oriente basin because of their capacity to lift large amounts of fluids, commonly in mature fields. However, this technology has a limited run life and is prone to intervention and operational challenges. This proposal aims to reduce intervention time and operating costs in multizone wells using rigless technology. Compared to traditional well interventions, rigless ESP permits a replacement operation in a shorter time, thus, reducing cost and deferred production. The company completed a drilling campaign in the southern area of the Mariann field, obtaining outstanding results during the first months of production. The operator considered producing several reservoirs simultaneously using modern completion techniques as a viable alternative to accelerate production from these wells. The acquired experience in the first two wells completed with rigless ESP technology in the Tarapoa Block allowed us to illustrate the technical and economic advantages of combining rigless technology with intelligent completion systems. This paper describes the current state of this technology in Ecuador. It addresses several important aspects such as completion design, ESP selection, nodal analysis, and production planning from Lower U and Basal Tena reservoirs. Economic implications of this technology compared to dual completions are also discussed. The candidate well was Mariann-56 due to its excellent reservoirs and remaining reserves. Based on production engineering and economic analysis, this study confirmed the feasibility of rigless multizone technology and improved the field's learning curve in multizone wells. The most significant results indicate that the company could reduce intervention time by more than ten days, representing an 80% reduction in time typically used for an ESP replacement using a workover rig. The operator could also optimize the project's economics by approximately USD 1.1 million in the first intervention related to deferred production and intervention costs. In addition, managing water cut using flow control valves maximizes well performance and provides better economic results. The following paper consists of a complete engineering and economic study useful for the decision-making process that will serve as a guide to improving ESP cost efficiency in multizone completions.