Hydrate Formation and its Influence on Natural Gas Pipeline Internal Corrosion Rate

Abstract

Hydrate formation along the natural gas pipeline has been identified as a serious threat to the survival of oil and gas industry. The formation if not quickly removed may plug the flowline to collapse the system. This problem costs the industry billions of dollars in revenue loss annually. While all the available literatures on hydrate formation process have focused on its ability to plug the flow line, there has been little or no recognition of its ability to initiate internal corrosion of the pipeline which is a bigger problem to the industry, hence, the importance of this study. This work focuses on this new area for research interest aimed at revolutionalizing the field of corrosion science and technology. In this study, the composition of the lattice which includes methane (CH 4 ), carbondioxide (CO 2 ) or hydrogen sulphide (H 2 S) and water molecules (H 2 O) amongst others is considered. These gases have the ability to easily undergo chemical and/or electrochemical reactions with the pipeline's internal surface while the lattice is in place. The reaction(s) will easily initiating corrosion of the pipe. The study further identifies the fact that even after the successful removal of the hydrate, the initiated corrosion process may continue with the continuous flow of the fluid within the pipeline thereby leading to gradual degradation of the material and deterioration of the pipe's integrity. Over time, the pipeline will begin to leak and/or may undergo full bore rupture (FBR). This, apart from the economic consequences will also generate environmental and political consequences and may lead to complete replacement of the pipe-length. Various management schemes including the necessity for the industry to heavily invest in research and development are recommended.

An assessment of hydrates inhibition in deepwater production systems using low-dosage hydrate inhibitor and monoethylene glycol

“…• Operating regime • Design • Geothermal gradient in the well • Fluid composition Key effects that hydrates plugs can cause include the blocking of production pipeline-riser systems, blocking of subsea transfer lines, forming in the wellbore, blow-out preventer and choke lines; in the event of gas-kick, thereby affecting drilling operations. It is also important to note that the partial or complete plug of the inner part of a gas pipeline, if not quickly removed, develops into high-pressure build-up inside the pipeline and leads to subsequent collapse of the pipeline (Obanijesu et al 2010).…”

Hydrate Anti-Agglomerants for Sour Gases with Corrosion Inhibitor Properties

“…Hundreds of millions of US dollars is spent on various hydrate prevention strategies; offshore companies spending US$1 million per mile on insulating subsea pipelines to prevent hydrates. 2,3 Hydrate treatment and prevention programs involve the application of non-chemical and chemical means. The non-chemical means include pigging to remove blockages, application of heat or reducing pressures but sometimes these can exacerbate the situation.…”

“…2 Use of large amounts of methanol may lead to corrosion problems since methanol dissolves corrosion inhibitors, and KHIs may not be compatible with corrosion inhibitors. Antiagglomerate some of which are surfactants tend to work at higher subcooling compared to kinetic hydrate inhibitors and are compatible with corrosion inhibitors.…”

The influence of corrosion inhibitors on hydrate formation temperature along the subsea natural gas pipelines

“…Corrosion inhibitors generally possess surfactants properties (El-Mahdy et al, 2013) and surfactants have been established to aid hydrate formation (Mandal and Laik, 2008). Hydrate formation is one of the major flow assurance problems in pipeline engineering; it annually costs the gas industry millions of dollars for its minimization and billions of dollars on the eventual consequences (Obanijesu et al, 2011). Gas hydrates are ice-shaped, crystal lattice, solid compounds formed by the physical combination of water molecules with small paraffinic homologous hydrocarbon molecules (C 1 -C 4 ) and the non-hydrocarbon components (CO 2 , H 2 S, N 2 , etc) at high pressure and low temperature due to the weak Van der Waals forces and the hydrogen bonding properties of water (Chapoy et al, 2010;Zhang et al, 2011).…”