The natural gas hydrate resources in the South China Sea alone are about 85 trillion cubic meters. In the drilling process of marine gas hydrate, the natural gas hydrate will decompose and produce gas, as the rising of temperature and dropping of the pressure in the annulus. This process will have a significant impact on drilling safety. Therefore, it is necessary to study the wellbore temperature distribution during the drilling of marine hydrate layer. In this paper, the wellbore temperature distribution of safe drilling in hydrated formation is taken as the research goal, and the research status of relevant domestic and international wellbore temperatures was investigated. According to the characteristics of the marine environment and reservoir-forming characteristics of hydrate reservoirs in the South China Sea, the wellbore temperature distribution model of offshore drilling wellbore under the condition of hydrate decomposition was established. The temperature distribution curve of drilling straight wellbore in hydrate layer of South China Sea was obtained. When drilling the hydrate reservoir, the distribution regularity of the wellbore temperature is similar to that of the conventional offshore drilling wellbore. However, the temperature of the wellbore annulus near the hydrate decomposition site is lower than the ambient temperature, mainly due to the hydrate decomposition endothermic. In this paper, the sensitivity analysis of several main parameters of the wellbore temperature distribution of drilling straight wellbore in hydrate layer of South China Sea was carried out. Through the conduction of experiment and numerical simulation, we have get some new findings: (1) The hydrate saturation has little effect on the wellbore temperature; (2) As the drilling fluid displacement increases, the annulus temperature of the wellbore above the mudline increases, and the temperature of the wellbore below the mudline decreases continuously; (3) As the density of the drilling fluid increases, the temperature at the wellhead decreases, and the temperature at the bottom of the well increases slightly; (4) The greater the rate of penetration of the well, the temperature at the upper part of the wellbore decreases, and the temperature at the bottom of the wellbore increases; Among them, the penetration rate has the most obvious effect on the annular temperature. The results are expected to be helpful to guide the drilling process of marine gas hydrate and offer some references.

仅南海地区天然气水合物资源量约85万亿立方米。在海洋天然气水合物钻井过程中，随着环空温度的升高和压力的下降，天然气水合物会发生分解产气。这一过程将对钻井安全产生重大影响。因此，有必要研究海洋水合物层钻井过程中的井筒温度分布。本文以水化地层安全钻井的井筒温度分布为研究目标，对国内外相关井筒温度的研究现状进行了调查。根据南海水合物储层海洋环境特征和成藏特征，建立了水合物分解条件下海上钻井井筒的井筒温度分布模型。获得了南海水合物层直井钻孔温度分布曲线。钻井水合物储层时，井筒温度分布规律与常规海上钻井井筒温度分布规律相似。然而，水合物分解位点附近的井筒环空温度低于环境温度，主要是由于水合物分解吸热。本文对南海水合物层钻井直井井筒温度分布的几个主要参数进行了敏感性分析。通过实验和数值模拟的进行，我们得到了一些新的发现：（1）水合物饱和度对井筒温度影响不大；(2)随着钻井液排量的增加，泥线以上井筒的环空温度升高，泥线以下井筒的温度不断降低；(3)随着钻井液密度的增加，井口温度降低，井底温度略有升高；(4) 井下钻速越大，井筒上部温度降低，井筒底部温度升高；其中，穿透率对环空温度的影响最为明显。研究结果有望对指导海洋天然气水合物的钻探过程有所帮助，并提供一定的参考。(1)水合物饱和度对井筒温度影响不大；(2)随着钻井液排量的增加，泥线以上井筒的环空温度升高，泥线以下井筒的温度不断降低；(3)随着钻井液密度的增加，井口温度降低，井底温度略有升高；(4) 井下钻速越大，井筒上部温度降低，井筒底部温度升高；其中，穿透率对环空温度的影响最为明显。研究结果有望对指导海洋天然气水合物的钻探过程有所帮助，并提供一定的参考。(1)水合物饱和度对井筒温度影响不大；(2)随着钻井液排量的增加，泥线以上井筒的环空温度升高，泥线以下井筒的温度不断降低；(3)随着钻井液密度的增加，井口温度降低，井底温度略有升高；(4) 井下钻速越大，井筒上部温度降低，井筒底部温度升高；其中，穿透率对环空温度的影响最为明显。研究结果有望对指导海洋天然气水合物的钻探过程有所帮助，并提供一定的参考。