深水海底泵举升钻井井筒泥浆性能、温度和压力场耦合规律

 井筒温度和压力场计算是深水海底泵举升钻井设计的重要内容.综合考虑温压场与泥浆性能,特别是泥浆流变性能的相互影响,建立深水海底泵举升钻井井筒传热和流动耦合计算模型,并与常规隔水管钻井计算结果进行比对.结果表明:受海水低温影响,上部井段环空温度小于入口温度,海底泵举升钻井井筒温度小于常规隔水管钻井,需注意低温时天然气水合物形成带来的安全隐患;海水段和地层段压力存在不同的压力梯度,地面泵压小于循环压耗,海底泵举升钻井井筒压力小于常规隔水管钻井;考虑泥浆密度和泥浆流变性能变化对井筒温度、ECD 和泵压均有影响,相对来说,ECD 受前者影响较大,而井筒温度场和泵压受后者影响较大;两者都考虑,泵压计算误差将大大降低.

Coupling laws of mud property,flow and heat transfer in borehole of deepwater subsea mud lift drilling

The calculation of wellbore temperature and pressure is an important part in deepwater subsea mud lift drilling (SMD) design. Considering the influence of temperature, pressure and mud property, this study established a model of flow and heat transfer in the borehole of SMD. The results show that affected by the low seawater temperature, the upper wellbore annulus temperature was lower than the mud entrance temperature; the temperature in the borehole of SMD was lower than that of regular deepwater drilling; the potential safety problems caused by gas hydrate formation need to be watched. The pressure gradients in the borehole were different between the sea section and underground section. The pump pressure above the ground was lower than the circulating pressure loss, and the pressure in the borehole of SMD was lower than that in regular drilling. Both mud density and viscosity had impact on the equivalent circulating density (ECD) and pump pressure and temperature in the borehole, while the former had relatively large impact on ECD, and the latter had relatively large impact on the pump pressure and temperature. When both were considered, the calculation error of pump pressure would be greatly reduced.