基于多普勒测量技术的深水隔水管气侵早期监测研究

摘要

In order to decrease the possibility of blowouts and explosions in deepwater drilling and for early detection of spills ,the early monitoring of gas cut to deepwater riser was investigated .Based on the discipline of wellbore gas cut distribution in the deepwater drilling ,the Untouched Ultrasonic Doppler Measuring System(UUDMS)was applied in a deepwater environment to detect the variation of gas cut in deepwater riser .In case that the continuous phase consisted in a water-based drilling fluid ,and by changing the flow velocity of drilling fluid and gas void fraction ,it was possible to analyze the changing characteris-tics of UUDMS signal .By averaging the voltages of signals under different void fraction conditions ,the re-lationship between the UUDMS signals and gas void fraction was obtained .Results showed that the aver-age voltage of the signals from UUDMS increased with increasing gas void fraction .When the void fraction was lower than 1% ,the distance between the mid-value of the probability distribution of signals with gas cut and that without gas cut was 55 mV .When the void fraction was larger than 3% ,the distance was 200 mV ;and the distance increased with increasing void fraction .Results from experiments showed that by u-sing the Untouched Ultrasonic Doppler Measuring System ,gas cut to deepwater riser could be detected in time ,which could save a significant amount of time in well control .%为减少深水钻井中的井喷及井喷爆炸事故，及时发现溢流，通过分析深水钻井中井筒侵入气的分布规律，利用非接触式超声波多普勒测量系统对深水隔水管气侵进行了研究。在连续相为水基钻井液的情况下，通过改变钻井液流速和含气率，分析了超声波多普勒信号的变化特征。通过处理实时采集的不同含气率下的测量信号电压并进行平均，得到了超声波多普勒测量信号随含气率的变化曲线，测量含量随含气率增大呈上升趋势：在含气率小于1％时，超声波多普勒测量信号概率分布和不含气情况下概率分布的中心线之间的信号差小于55 mV ；在含气率达到3％后，与不含气情况下概率分布中心线间的差变为200 mV ，且随着含气率上升有进一步增大的趋势。试验研究表明，用非接触超声波多普勒测量方式研究深水隔水管中的含气情况，能及时发现地层气体侵入隔水管，为井控赢得时间。