Optimal design of the engineering parameters for the first global trial production of marine natural gas hydrates through solid fluidization

Self Cite

In recent years, marine hydrate has attracted more and more attentions. As a creative way to efficiently exploit marine hydrate, the method of solid fluidization exploitation is to excavate and crush hydrate, transport hydrate particles to sea surface platform through airtight pipeline, and obtain methane gas finally. When hydrate particles are transported up, as temperature rises and pressure drops, hydrate will decompose at a certain critical position and produce a large amount of gas, bringing complicated gas‐liquid‐solid multiphase non equilibrium pipe flow, and seriously threating well control securities. Thus, we establish mathematical models of wellbore temperature and pressure, hydrate phase equilibrium, hydrate dynamic decomposition in riser pipe flow and wellbore multiphase flow coupling hydrate dynamic decomposition, and propose and verify numerical calculation method. Then numerical model application analysis under different construction parameters is carried out, influence behaviors of multiphase non equilibrium pipe flow are obtained, and field construction measures are put forward. Properly increasing solid throughput can increase production of natural gas. However, problems such as well control risks will intensify. Therefore, delivery capacity, liquid density, and wellhead back pressure should be increased appropriately at the same time. This study provides important technical support for solid fluidization exploitation of marine hydrate.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Multiphase non equilibrium pipe flow behaviors in the solid fluidization exploitation of marine natural gas hydrate reservoir

Wei

Sun

Meng

et al. 2018

Self Cite

An experimental study on the startup velocity and motion characteristics of sand beds in air–water pipelines

Zhang

Yang

et al. 2022

Sand deposition in the wellbore is one of the most common problems in oil-gas and hydrate exploitation work. A detailed understanding of the migration characteristics of the sand bed and accurate prediction of the starting velocity of the sand bed are key aspects of effective sand carrying.Therefore, this study conducted a large-scale outdoor gas-water-sand threephase flow experiment. The effects of critical factors such as flow pattern, sand size, sand bed height, and pipe inclination angle on sand bed startup velocity and migration were studied experimentally. The experimental results indicated that during the startup process of the sand bed, sand particles exhibited three states: rolling, jumping, and suspension. During the experiment, the sand bed morphology included a static bed, rolling bed, jumping bed, and suspension bed. Compared to a stratified flow, intermittent flow and agitated flow were more beneficial for the startup velocity of sand beds. An increase in pipe inclination also reduced the starting velocity of the sand bed. With an increase in sand size, the startup velocity of the sand bed increased correspondingly. However, there was no significant influence on the migration morphology of the sand bed. Additionally, the greater the thickness of the sand bed, the lower the starting velocity of the sand bed. Based on the stress states of sand grains, in combination with experimental data, this study used least-squares estimation to establish a prediction model for the startup velocity of sand beds. The model prediction results were in good agreement with the experimental data. This study will provide a basis for predicting the startup velocity of sand beds during the gas-liquid two-phase sand-carrying process.

Assessment of forecasting hydrate blockage in foam drainage gas recovery wellbore

Zhang,

Wei,

Cai

et al. 2024

Hydrate formation in foam drainage gas recovery wells and the shut in accidents caused by plugging have become an important problem that restricts the safe production of natural gas. The blockage and accumulation of hydrates is a gradual problem. This research goes beyond predicting the formation of hydrates and delves deeper into examining the rate of hydrate formation and the degree of pipeline blockage at different wellbore locations. First, the temperature model, pressure model, multiphase flow model, and hydrate plugging model of hydrate formation process are established from the equations of mass conservation, energy conservation, and momentum conservation. Second, an iterative approach is employed to solve the model, with a maximum error of 6.86% in model validation. Finally, sensitivity analysis shows that wellhead temperature, wellhead pressure, and foam viscosity have different effects on hydrate formation, maximum plugging position, and plugging degree. At the same time, combined with the actual drainage and gas production process, and the characteristics of hydrate blockage, proposed hydrate prevention measures can be taken to achieve safe production of natural gas. The research results indicate that a decrease in temperature signifies an increase in undercooling, resulting in an accelerated rate of hydrate formation and an elevated risk of hydrate blockage. The decrease in wellhead pressure leads to a decrease in the rate of hydrate formation and an increase in production, which is beneficial for the hydrate prevention. However, larger pressure differences and gas production rates will put higher requirements on equipment such as well control devices. An increase in foam viscosity will lead to increased pressure, foam compression, reduced drainage capacity, and intensified hydrate generation. Therefore, foam viscosity should be kept as small as possible to keep the foam stable.