Study on Sand Production in Natural Gas Hydrate During Radial Wells Depressurization Exploitation

Abstract

Abstract Radial wells are recognized as a promising type of well for achieving the commercial development of natural gas hydrate (NGH). Previous research has confirmed the positive impact of radial wells on enhancing the efficiency of NGH exploitation. However, the impact of radial wells on the reservoir intensifies pressure transmission and hydrate dissociation during the hydrate extraction process, significantly increasing the risk of sand production. Furthermore, in contrast to conventional reservoirs, hydrates in the South China Sea (SCS) are primarily hosted in unconsolidated argillaceous siltstone reservoirs. These reservoirs have poor cementation and weak stability, leading to an increased risk of sand production. This study aims to investigate the issue of sand production in radial well exploitation by constructing a three-dimensional thermal-hydrologic-mechanical-chemical coupling model based on the reservoir parameters in the SCS. The analysis focused on variations in production capacity, sand production, and stress distribution between vertical wells and radial wells during the depressurization exploitation processes. Furthermore, a sand control standard is proposed to assess the impact of sand control on radial well exploitation. The results show that: 1) Under the present simulation conditions, the annual gas production of radial wells is increased tenfold compared to vertical wells, but the problem of sand production is more serious. 2) Stress concentrations are the most serious problems that occur during hydrate exploitation, particularly in the near wellbore and perforation sections. 3) Raising the sand control standard for radial wells can effectively alleviate sand production issues but may lead to a decrease in exploitation efficiency. In summary, this paper offers valuable insights and guidance for managing sand production and sand control in NGH exploitation through radial well depressurization.