ABSTRACT:

Research shows some progress has been made in natural gas hydrate exploitation, but there is no great breakthrough in technology. According to the characteristics of gas hydrate, this paper puts forward a new model based on the traditional geothermal method. Firstly, to inject sea water into the heat exchanger which is laid in the geothermal layer through the string. The lower part of the pipe string is blocked by a packer. Due to the influence of geothermal layer, the seawater in the U-type tube heat exchanger can be changed from liquid state to gas state, and the hot steam rises rapidly. Through the fracture, it enters the gas hydrate reservoir in order to accelerate the development of natural gas hydrate to improve its yield and recovery. In addition, the extracted natural gas and steam are recycled to the steam turbine to drive the turbine so we can realize geothermal power generation. The concept integrates drilling and power generation devices, and greatly reduces the operation cost on the basis of multifunctional development model.

1. Introduction

Natural gas hydrate is a clean and environment-friendly alternative energy source with large reserves and high energy density, which has not been exploited on a large scale yet (Chen et al., 2020; Tan et al., 2016; Wang et al., 2018; Oveckiy et al., 2016). Therefore, it has far-reaching utilization value for alleviating energy crisis. Decomposition of natural gas hydrate (NGH) is an endothermic process, thermal stimulation method can provide energy for the decomposition of the hydrate, thus can greatly improve the decomposition rate of natural gas hydrate, achieve better development effect (Sun et al., 2019; Li et al., 2015; Wang et al., 2018). However, conventional thermal stimulation method requires a lot of investment and cost of thermal ground, economical efficiency, at the same time the ground formed in the process of the thermal fluid flow will consume a large amount of fossil energy and produce a large number of harmful gas, environmental protection (Kumari et al., 2018; Sasaki et al., 2010). In order to improve the efficiency of gas hydrates exploration, this paper based on the traditional method of geothermal exploitation of hydrate puts forward the new method. First of all, the heat exchanger is laid in the geothermal layer, due to the affected by geothermal layer, sea water converts to steam, then it rises rapidly through fracturing cracks into the hydrate reservoir to improve their production and recovery factor. This method does not require hydraulic fracturing of the geothermal layer, which saves the cost and reduces the damage. In addition, compared to the exploitation of natural gas hydrate by thermal stimulation method, it does not need to use fossil fuels to heat the fluid, so it is low-carbon and environmentally friendly (Sakamoto et al., 2004).

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