First Application of Multistage Completion & Acid Fracturing in Deep Carbonate Reservoirs in Kuwait

Abstract

Abstract Drilling horizontal wells into a heavily fractured sour Jurassic reservoir and resorting to acid fracturing may be the key to unlocking substantial reserves of oil for Kuwait. Horizontal wells, while more technically challenging and expensive, will ensure fractures are encountered and acid fracturing will penetrate multiple large, oil bearing fractures to improve productivity. This paper highlights the well design, planning, challenges, operational complications and results of the application of multistage completion & acid fracturing in a deep carbonate reservoir in one of Kuwait's field. The aim of the application of such a distinctive completion was to enhance the production from horizontal well in low permeability carbonate reservoir in West Kuwait. A series of directional technologies and techniques were used in this application. These included a benign build profile, use of RSS motors in kick-off, curve and drain hole for enhanced steering capabilities, lateral drilling with PDC bits. The ability to drill the well without gains or differential sticking was a major challenge and one which was addressed with the close control of fluid design, mud weight window and hole cleaning policy. A horizontal well was drilled to a TD of more than 15,500 ft with 7 casings policy with one sidetrack. In view of the multistage completion, which requires the hole to be clean of any debris so that the hydraulic ports and ball seats remain obstruction freefor allowing droping of balls, a conscientious decision was made to lower a 7 ¾? tie-back prior to lowering completion. The operations involved a series of steps performed for the first time in Deep Drilling with primary consideration to limit generation of metallic debris while employing judiciously the use of cleanup tools to get rid of the drilling generated metallic fines. This was followed by a simulated reamer assembly trip performed to ensure the successful lowering of completion assembly. The paper discusses the challenges of horizontal drilling through formations prone to differential sticking, preparation of the hole for and lowering of multistage frac completion and fracturing. The well yielded favorable results with high oil production which showed great potential for increasing Productivity. While such completion will lead to enhanced productivity, lessons learned include among others a step ladder process to make lowering such a completion consistently successful. Being the first application in deep reservoirs, the lithology has opened up a new dimension for tapping the full potential of the horizontal wells being drilled. This is likely to enhance production in future.