Multilateral Technology Enables Record Reservoir Contact in North Sea Subsea Well

Abstract

Abstract In the 1990's many oil plays in the North Sea were originally deemed uneconomical due to the limited technology available to address the associated challenges. Horizontal and eventually multilateral applications were introduced to address this challenge. For over two decades multilateral technology has extended the production life of these fields by continuing to evolve to meet the demands of increasingly complex subsea applications. Over this history, multilateral applications have evolved from dual-laterals with standalone screens and commingled flow to tri-lateral and quad-lateral intelligent completions as common multilateral completion strategies in the North Sea. A significant number of wells originally completed as a dual-lateral have since been recompleted twice or even three times to produce reserves previously left behind. As investment and availability of new fields decline, operators face challenges to extend the production life of mature fields while also working to reduce overall development cost, cycle times, and carbon footprint. Further challenges include delivery of wells and facility systems using less in-field construction hours at a lower baseline cost. This paper will focus on the evolution of a mature well in a region that has been installing multilateral wells for over two decades. Originally drilled as the world's first tri-lateral well and several years later re- drilled again as a quad-lateral to add further reservoir contact. As production decline and strategic targets esteemed to be more profitable are within reach from the same template, further re-drills as a dual-lateral and then a further quad-lateral has been utilized to add significant reservoir contact for further economic production. It highlights the technology used to keep this well on production for over two decades and the benefits of expanding the use of this technology as fields become slot restricted. It also highlights the benefits this technology delivers in significantly increasing reservoir exposure and the time savings brought by drilling new lateral legs in existing subsea wells. The case study will include discussion of workover operations, completions, isolation methods, and lateral creation systems. Through four separate multilateral installations in one subsea slot, the production life has been extended beyond 20 years. The paper also provides insight as to methodology for continually improving reliability of multilateral installations to maximize efficiencies.