Experimental simulation of mixed deposition of hydrate and wax in a deepwater subsea pipeline

Abstract Hydrate and wax deposition are the main challenges faced by the safe operation of a deepwater subsea pipeline due to low temperature, large elevation difference, and complex multiphase flow conditions. Chemical agents are important ways for treating hydrate and wax deposits. Oil, gas, and water produced by Liuhua 16-2 Oilfield are selected as experimental media to test and evaluate independently developed pour point depressants, wax deposition plugging removal agents, and low dose hydrate kinetic inhibitors. The static effect test results for three pour point depressants AN-12B, OF-1, and JN106-12B show that JN106-12B has the best performance, which can reduce the pour point of crude oil produced by Liuhua 16-2 Oilfield from 8°C to -19°C. When there is a risk of mixed deposition and blockage of hydrates and waxes during the fluid flow in the loop, simply adding pour point depressants or hydrate kinetic inhibitors cannot reduce the critical temperature at which the loop blockage occurs, and adding only wax deposition and blockage removal agents after the loop blockage cannot achieve blockage removal. However, if thermodynamic hydrate inhibitors such as methanol are added in advance, after the pipeline is blocked by wax deposition, the pipeline can be unblocked by adding the wax deposition unblocking agent JD150-B27. 20000ppm wax deposition plugging remover JD150-B27 takes about 40 minutes to achieve loop plugging removal. The evaluation results of different agents provide an important reference for the prevention and control of hydrate and wax deposition in the subsea pipeline of Liuhua 16-2 Oilfield.