为保障深水高温高压气井的完整性和预防温度波动导致钻井液体积显著变化进而引起环空压力的风险，准确预测钻井液的热膨胀系数是进行评估和控制环空压力的关键因素，因此采用钻井液PVT（压力-体积-温度）特性实验，拟合得到对应温度-压力范围内钻井液的热膨胀系数，根据拟合公式建立相应的基于实测钻井液的热膨胀压力的预测模型并验证，形成一套深水高温高压气井基于实测环空热膨胀压力预测方法。结果表明，水下井口环空温度在生产后期降低，但高于泥线温度，导致热膨胀压力增加。管内流体压力随产量降低，增加管柱失效风险。基于钻井液PVT特性实验，预测了流体热膨胀系数，发现其随产量和地层压力变化显著，降低率可达38.9%。钻井液Ⅱ在控制环空热膨胀压力方面表现更优，推荐用于管理环空压力。

To safeguard the stability of deep-sea wells under high temperature and pressure, and to avert the hazard of substantial alterations in the drilling fluid's volume that could be triggered by temperature shifts, which may lead to the risk of annular pressure, accurate prediction of the thermal expansion coefficient of the drilling fluid was a key factor in assessing and controlling the annular pressure. Therefore, through the experiments on the PVT characteristics of drilling fluids, the coefficients of the drilling fluid's thermal expansion were fitted to the corresponding temperature-pressure ranges, a corresponding predictive model was constructed and confirmed, utilizing the formula for fitting. Drawing on the fitting formula, a corresponding prediction model based on the measured thermal expansion pressure of drilling fluid was established and verified to form a set of prediction methods for the thermal expansion pressure of deep water high-temperature and high-pressure gas wells based on the measured circumferential pressure. The results show that the annulus temperature at the subsea wellhead decreases in the late production period, however, it exceeds the temperature at the mudline, resulting in an escalation of the thermal expansion pressure. The fluid pressure within the tubing diminishes as production progresses, increasing the risk of tubing column failure. Based on the drilling fluid PVT characterization experiments, the fluid thermal expansion coefficient was predicted and found to vary significantly with production and formation pressure, with a reduction rate of up to 38.9%. Drilling fluid Ⅱ performs better in controlling the thermal expansion pressure in the annulus and is recommended for managing annulus pressure.