Flexible Pipes Integrity Assessment in Field Campaign with Novel Mobile Annulus Testing System

Abstract

Flexible pipes annulus condition is a key concern regarding the pipe's integrity. The presence of water in the annulus may lead to a corrosive environment which reduces the fatigue life of the tensile armours. Annulus flooding is the most frequent failure case [1] and may occur due to a failure on the external sheath, failure of the end fitting sealings or failure of the vent valves installed in the end fittings. Water may also reach the annulus not from the outside but as condensation of the permeated gases from the bore. One of the current approaches to assess the annulus condition consists in the detection of annulus flooding through free volume measurment by means of a positive pressure test or a vacuum test. This intervention may be complemented by gas sampling from the annulus and measurement of bore-to-annulus gas flow permeation rates. Conventional venting systems on the top end fitting typically do not allow for these operations but for approximations of permeation flow rate by monitoring of annulus pressure build-up because of pressure sensors installed in the venting system. To address flexible pipes integrity, the Mobile Annulus Testing System (MATS) was developed. MATS allows for the determination of free annulus measurement, by means of conventional positive pressure or vacuum testing. Moreover, MATS allows for permeation gas flow rate measurement and gas sampling. Also, MATS is easily deployable and can be transported as cargo on flight helicopters. MATS was tested on a field campaign in 09 flexible risers in the Tupi Field in Santos Basin, brazilian pré-salt, and this paper presents the results obtained.