Investigation On Sulfur Deposition Of The Natural Gas Gathering System

The sulfur deposition has always been an important and difficult problem in thedevelopment process of gas reservoirs with high H2S content. Most past researches focusedon gas reservoirs and bore holes, the elemental sulfur deposition problem in the natural gasgathering system has been emphasized by scholars only in recent years. In the developmentand processing of gas field, this deposition can cause serious corrosion and block in pipelinesand other facilities. As a result, accurate description and analysis of the mechanism andinfluential factors of sulfur deposition, deep unstanding of the law of elemental sulfurdeposition and the development of scientific and efficient prevention and control technologyhas become one of today’s key issues and difficulties in domestic and foreign exploration ofhigh sulfur content natural gas.This research project has been able to identify the type and mechanisms associated withthe formation and deposition of ‘elemental sulfur’ in natural gas gathering pipelines andassociated equipment. A model is developed to predict the solubility of elemental sulfur inhigh sulfur content natural gas and numerical simulation on the flow field in the pipeline hasbeen carried out using the commercial computational shareware-Fluent. The new technologieswill be applied in the wellhead to prevent and control the sulfur deposition.There are two kinds of sulfur deposition mechanisms: nucleation and moleculardiffusion. Based on a new discovery of the equivalent thickness sulfur deposition layer in theinternal wall of the pipeline, the mechanism of formation is also presented: one part of sulfurparticles adhere to the internal wall surface in the presence of gas pulsation and Brownianmotion; the other part of sulfur particles migrate to the internal wall surface in the presence oftemperature gradient and velocity gradient; the deposition has the property of shear-thinning behavior, so the deposition becomes the equivalent thickness with the action of gas flow.Based on the principle that gas and solid fugacity are identical in both phases, the model topredict the solubility of elemental sulfur in high sulfur content natural gas is developed. Therough surface can promote the deposition of sulfur.The ‘dead zone’ is located immediately downstream of gate valve. The ‘dead zone’accelerates the deposition rate of sulfur particles, and at the same time, it decreases thecarrying rate of gas flow. The turbulence of the flow field located downstream of the butterflyvalve increases the probability of collision of particles with a wall. The deposits of elementalsulfur are most commonly found at the middle of manifold.Relationship between the hydrate formation conditions and sulfur deposition is analyzed.Gas hydrate forms more easily with a higher H2S content. The sulfur particles can promotethe formation of hydrates by being the nucleuses.