Significant Reduction of Well System Fatigue by Use of Reactive Flex Joint with Integrated Monitoring System

Abstract

Abstract Operators working on shallow and mid-water depths in rough seas are focusing on reducing fatigue in the upper part of well systems during drilling operations. Fatigue is caused by cyclic bending moments due to wave induced riser and vessel motions. The combined use of a Reactive Flex-Joint (RFJ) and the Well Access Management System (WAMS) has demonstrated significantly reduced fatigue exposure through a reduction in loads, reporting of real-time status and rig positioning advice. The RFJ is a mechanism mounted on a standard flex joint for easy installation on drilling rigs. It uses a nitrogen gas spring to reverse the flex joint bending moment. The generated opposing moment increases with an increasing angle of the lower flex joint. This significantly reduces the cyclic bending moments in the lower part of the Blow Out Preventer (BOP) and wellhead (WH) system. WAMS is an advanced monitoring system that may be operated as a fully integrated part of the RFJ design. Sensors provide real-time data for flex joint angle, BOP inclination, wellhead- and riser bending moments. The data is used to assess incurring fatigue damage in real-time and for reporting fatigue status after operations. Two RFJ systems have been in continuous use on two separate rigs during 2020. The RFJ system and WAMS are field-proven and have demonstrated their efficiency in challenging operations in the Barents Sea and the North Sea. The RFJ has been well received in the market due to one-time installation, safe use, significant reduction in wellhead loads, and low operating expenses (OPEX). Data obtained from the operations have been carefully analyzed and show that the RFJ reduces cyclic loads from 50 to 80% resulting in 30 to as much as 1000 times extended fatigue life of the wellhead. The RFJ efficiency depends on the settings of the system and operational conditions.