Considerations and Lessons Learned on Development of Gas-Lift Paraffin Inhibitors for Subsea Wells in the Gulf of Mexico

Abstract

This paper details the laboratory evaluation and product development for auniquely applied gas-lift paraffin inhibitor. Several crude oils, specific toone particular Gulf of Mexico subsea network, were characterized with respectto cloud point, pour point and paraffin content. This information was used todetermine suitable wax inhibitors to test for application into the productionfluids offshore. Cold finger wax deposition tests were performed to evaluateeight different inhibitor chemistries. Details are given on the test methodologies used, with particular focus on thespecific evaluation to determine gas-lift suitability. Volatile flash analysiswas performed by a third party laboratory, coupled with a unique dynamicgas-lift test method, to find a suitable candidate. Of the products tested, twonew and specific formulations were developed for gas-lift applications thatdisplayed low weight loss and very little increase in viscosity. There is very little documented in open literature on the formulations and testmethodologies employed to evaluate paraffin inhibitors for gas-liftapplication. This paper describes the most important treatment parameters anddetails on how gas-lift application was performed. This includes somesignificant learning lessons on the design and implementation of gas-liftparaffin inhibitors, as well as conclusions regarding the most appropriatedeployment parameters to avoid gunking and clogging of injection systems. Italso details the specific chemistries that can and should be used for this typeof application. Introduction Paraffin Deposition from Crude Oil Crude oils naturally contain paraffinic, waxy components, defined as aliphatichydrocarbon molecules with the empirical formula CnH2n+2 (n is most commonly>18). Paraffin can exist in three forms:Macrocrystalline: these tend to be dominated by straight chained n-alkanesand are classically defined by paraffin deposits found in subsea and exportpipelines.Semi-microcrystalline: this is an intermediate form of macro- andmicrocrystalline paraffin.Microcrystalline: these tend to be cycloalkanes and branched alkanes oftenassociated with asphaltenes and other solid deposits. These are normallyencountered in tank bottoms as a sludge-like deposit. Paraffin precipitation increases the viscosity of crude oil creating higherdrag and pressure. Deposition on the walls of tubulars, flowlines and pipelinescan increase surface roughness and create a higher differential pressure. Physical restriction of the pipeline can also occur, creating less flow orincreased energy costs to maintain flow.

Flow Assurance Technologies for Mitigating Wax Deposition in Subsea Petroleum Production System

“…용매제는 Fig. 14와 같이 무극성인 왁스와 상호간 공 유결합을 이루어 왁스의 용해도를 높인다 (Dobbs, 1999;Wylde and Slayer, 2012). 용매제의 분자길이가 길어질 수록 왁스를 용해시킬 수 있는 성능이 더 증가한다 (Poole et al, 2008).…”