The gas hydrate reservoir has the problems of weak consolidation, shallow burial and difficult seepage, and is accompanied by complex phase and temperature changes during the development process. Therefore, the sand production problem in the development of gas hydrate reservoir seriously restricts its commercial development, and the sand control research in the development of gas hydrate is particularly important. Therefore, it is the basis of long-term safe and efficient development of hydrate to clarify the plugging rule of argillaceous silt in the sand control medium of hydrate reservoir. Therefore, this paper designed a set of visual simulation experiment device for sand control and plugging prevention, which simulated the sand control process of screen media. The results show that the precision of sand control is the key factor affecting the development of hydrate. The precision of sand control is too high, dense mud cake is formed on the surface of the medium, and the plugging is serious, which increases the resistance of fluid flowing from the hydrate reservoir to the wellbore, thus reducing the production of natural gas; If the sand control accuracy is too low, a loose sand bridge will be formed on the surface of the sand control medium. The sand control ability of the medium is poor and the sand production is serious; Due to the low temperature and high pressure characteristics of the reservoir, gas water fluid may adhere to the surface of the medium, increasing the degree of plugging of the medium. The research results have certain guiding significance for sand control in the process of hydrate exploitation. 

Study on Plugging Mechanism of Sand Control Medium in Hydrate Argillaceous Silt Reservoir

Based on the whole life cycle process of the economic exploitation of natural gas hydrate, this paper proposes the basic problem of stabilizing the wellbore for the basic conditions that must be met to ensure the integrity of the wellbore for exploitation: revealing the complex mechanism of fluid–solid–heat coupling in the process of the physical exchange of equilibrium among gas, water, and multiphase sand flows in the wellbore, hydrate reservoir, and wellbore, defining the interface conditions to ensure wellbore stability during the entire life cycle of hydrate production and proposing a scientific evaluation system of interface parameters for wellbore integrity.

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An Interface Parametric Evaluation on Wellbore Integrity during Natural Gas Hydrate Production

The paper investigates the heat transfer in the exploitation of offshore argillaceous‐silt natural gas hydrate reservoirs considering sand control. The temperature prediction model is established in this investigation. The coupled pressure‐temperature model of the flowing fluid inside the wellbore is also presented. The sand control for argillaceous‐silt natural gas hydrate reservoirs mainly brings two effects into the temperature and pressure profiles simulation, including the moderate sand control and the Joule–Thompson effect. The moderate sand control is reflected by the volume and particle size of produced sand into the wellbore in the mathematical derivation. The Joule–Thompson is considered in the model due to the small diameter of sand control screens. The experiment is designed to measure the pressure drop caused by various mesh diameters of sand control screens. Subsequently, the regression relationship between the pressure drop and the mesh diameter is concluded to calculate the temperature change at the sand control screen. The simulation of heat transfer helps to analyze secondary hydrate formation risk in the wellbore. The proposed model identifies the high‐risk location of the secondary hydrate formation. The sand control effect and well geometry effect are discussed quantitatively. The strict sand control in the argillaceous‐silt natural gas hydrate (NGH) sediment exploitation reduces the risk of secondary hydrate formation significantly; however, it also has a negative effect on natural gas production. To balance the sand control and the prevention of secondary hydrate formation risk, it is suggested to install the heating electrode in the high‐risk location to ensure flow safety with acceptable sand control precision. The heat provided by heat electrodes is calculated by the model presented in this paper. The model can be used to determine the proper arrangement of heat electrodes. The paper also describes the secondary hydrate formation by adjusting the well geometry. The formation depth of the NGH reservoir and the sea interval should be considered in the risk analysis of the secondary hydrate formation. Additionally, the effects of wall thickness and wall thermal properties are evaluated and discussed. It is recommended to optimize the riser thickness with a small thermal conductivity value to minimize the secondary hydrate formation risk, which is more efficient compared to adjusting the cement sheath.

Jinze Song

Papers

State‐of‐the‐art brief review on sanding problem of offshore natural gas hydrates sediments