Evaluation of the Hydrolysis Behaviour of PA in High-Pressure CO2 Environments

Abstract

Abstract In the latest offshore developments to be carried out in Brazil, supercritical CO2 (scCO2) injection into the fields is being considered as a potential application. This injection operation will gradually lead to high levels of CO2 in the produced fluids, creating additional challenges for the materials used in riser systems specifically designed for such applications. Upcoming developments are being carried out in ultra-deep waters which can reach 2500 m. Flexible pipes are considered one of the options for both production and CO2 injection pipes due to performance in such scenarios and fast implementation when compared with conventional rigid riser systems. However, the high levels of CO2 and the presence of water in the conveyed fluids has raised some questions about the utilization of polyamides in such applications, and the applicability of API 17 TR2 to properly predict the hydrolysis of polyamides in such extreme environments. Based on this new scenario, GE Oil & Gas has implemented a specific R&D program to evaluate the hydrolysis behavior of polyamides within environments containing high CO2 partial pressure, exceeding 400 bar. This paper summarizes the experimental results assessed during the test program carried out and discusses the applicability of polyamides in both oil/gas production and CO2 injection flexible pipes. Introduction Though CO2 reinjection into geological formations is not a new subject, in recent years its importance has gradually increased within the offshore industry, due mainly to adoption of carbon capture and storage (CCS) and enhanced oil recovery (EOR). The feasibility of offshore reinjection operations was demonstrated in 1996 with the development of the Sleipner field in Norway as part of a CCS project [1], and again in 2004 in Algeria with the development of the In Salah natural gas field [2] with approximately one million tons of CO2 per year being separated from the produced natural gas and then reinjected into the geological formation. In order to make CCS cost effective and economically feasible, the CO2 reinjection may be used as part of an EOR process to improve production and fight reservoir depletion [3]. The need for CCS is even greater in the development of offshore projects in the Brazilian pre-salt cluster in ultra-deep water, an environment with several technological challenges. According to Nakano [4] the produced oil in this new exploratory province will present a high gas : oil ratio (GOR) and the dissolved gas will present a CO2 concentration ranging from 8 to 12% during the first years of production. Based on this scenario, CCS and EOR programs will be put in place [4] [5] to comply with environmental regulations and make the project more cost effective.