隔水管内气液两相流声传播特性与深水钻井气侵监测方法

A large number of gas invading wellbore is the main cause of blowout and other disasters when drilling the high pressure gas reservoir in deepwater area. And early detection of gas invasion in wellbore is the key to control blowout promptly and effectively. The existing gas invasion monitoring technology is mainly dependent on the measurement of pit gain or export flow rate on ground or water surface. Currently, the regional water depth of deepwater drilling has exceeded 3000m, which makes monitoring of gas invasion in advance by installing the monitoring equipment in subsea become possible. If the use of acoustic wave to monitor two-phase flow characteristics in the subsea, it can achieve the early detection and real-time quantitative description of gas invasion in deepwater drilling. This project is just in response to this conception, which focus on the key scientific issues that the main sensitivities and response of two-phase flow characteristics within the riser and the characteristic parameters of acoustic signals. Meanwhile, using the method of combining experimental studies and theoretical analysis, it can reveal the propagation and quantitative characterization relationships of acoustic signals in the two-phase fluid with different gas-liquid ratio, and establish a quantitative relationship between the characteristic parameters of acoustic signals and the gas-liquid ratio of two-phase fluid. Finally put forward methods for measuring and monitoring the wellbore gas invasion through the acoustic wave propagation characteristics in the fluid of subsea riser. This can provide the theoretical basis for early and accurate monitoring of gas invasion in deepwater drilling, real-time quantitative description of gas invasion degree, and safe and efficient control technology.

深水高压气层钻井过程中气体大量侵入井筒是引起井喷等灾害的主要原因，尽早发现气体侵入井筒是及时有效控制井喷的关键。现有成熟的气侵监测技术主要依赖于地面或水面泥浆池增量或出口流量的测量。目前深水钻井的区域水深已经超过3000m，使得将监测仪器下入到3000m的水底提前监测到气体的侵入已成为可能。如果在海底利用声波监测隔水管内的气液两相流特征，可以实现深水钻井气侵的早期监测和实时定量描述。本项目就是针对这一构想，重点研究隔水管内气液两相流特征与声波信号特征参数的响应规律以及主要敏感因素这一关键科学问题，通过实验研究和理论分析相结合的方法，揭示声波信号在不同气液比两相流体内的传播规律和定量表征关系，建立声波信号特征参数与两相流气液比之间的定量关系。提出通过海底隔水管内流体声波传播特性测量监测井筒气侵的方法。为深水钻井气侵早期准确监测、气侵程度的实时定量描述和安全高效控制技术提供理论依据。

深水高压气层钻井过程中气体大量侵入井筒是引起井喷等灾害的主要原因，尽早发现气体侵入井筒是及时有效控制井喷的关键。目前深水钻井的区域水深已经超过3000m，如果在海底利用声波监测隔水管内的气液两相流特征，可以实现深水钻井气侵的早期监测和实时定量描述。本项目重点研究隔水管内气液两相流特征与声波信号特征参数的响应规律以及主要敏感因素这一关键科学问题，通过实验研究和理论分析相结合的方法，揭示声波信号在不同气液比两相流体内的传播规律和定量表征关系，建立声波信号特征参数与两相流气液比之间的定量关系。提出通过海底隔水管内流体声波传播特性测量监测井筒气侵的方法。.通过开展上述研究获得的主要结论如下：.1）建立了能够用于模拟隔水管超声波气侵监测的实验方法和实验系统，该系统可以实现不同钻杆转速（0-160r/min）、循环排量（0-0.5m3/min）、气体流量（0-10m3/h）、气泡大小及密度、超声波发射频率（0.1-2.25MHz）及安装位置（0-360°）等条件下的隔水管超声波气侵监测实验，实时采集实验中井筒环空进出口压力、超声波发射及接收信号等数据。.2）建立了一套完善的分析隔水管超声波气侵监测的理论和数值模拟方法，并通过实验验证了该方法的可靠性和准确性。该方法的优势在于弥补实验中无法精确控制气泡大小、密度及分布的问题，用于探究影响超声波在隔水管环空多相流中传播规律的深层次原因。.3）揭示了超声波信号在不同气液比两相流体内的传播规律和定量表征关系。筛选了声波敏感性特征参数，包括振幅峰值、波速、衰减系数以及主频等，并分析了各特征参数的适用范围。在此基础上，优选了接收探头的安装位置，提出了气泡非均匀分布条件下的气侵监测及定量描述方案。.4）提出了基于隔水管气侵监测数据的井筒气侵程度定量描述方法。基于隔水管超声波监测的截面含气率信息，利用井筒多相流理论对整个井筒的气侵情况（不同井深处的气液比）进行反演，结合井控相关要求对气侵程度进行风险等级划分，实时定量评估气侵井控风险。