The World's First Offshore Multilateral Well Completed with Multistage Proppant Fracturing: A Case Study from Offshore Black Sea

Abstract

The paper aims to present the successful execution of the first offshore multilateral well completed for multistage high-pressure proppant stimulation - in the Black Sea, offshore Romania. The paper describes the drivers that lead the operator to trial a multilateral well as well as cover the considerations made in selecting, defining and executing the final completion solution with a review of the lessons learned. With only one platform slot left and a significant undrained area of reservoir the operator had to maximise the hydrocarbon recovery through a single well which, due to pressure to increase the operator's daily production, had to be finalised in just one year. Building on field experience gained since 2008 in drilling and completing for multistage proppant stimulation a detailed screening and evaluation of multilateral completion technologies was performed. The focus was on developing a concept that would minimise risks during execution while meeting cost and lead time objectives, which necessitated customising the chosen TAML Level 3 completion design and installation methodology. To maximise rig-time efficiency the well was executed in two phases: 1) drilling and lower completion installation of both branches with a drilling rig and 2) stimulation and upper completion installation with the platform's workover rig. With six stages in each lateral the high-pressure stimulation was executed by a converted supply vessel in four sailings, necessary to reload materials. To meet the delivery schedule, ensure simplicity and utilise operator experience the completion was realised with no dedicated multilateral hardware, rather, through the effective use of standard multistage stimulation open hole completion equipment and appropriately engineered bent joints to exit the main bore. With initial production rates higher than anticipated, the multilateral well completed in this manner has proven to be considerably more economic than drilling two horizontal wells with equivalent reservoir coverage. The success of this well serves as a proof of concept and provides increased confidence in delivering reliable, cost effective multilateral wells even under tight time constraints and in areas and/or operators with no history of multilateral well completions