深水气井测试清井诱喷瞬态流动模拟

在深水气井测试作业中,由于缺乏对实际放喷过程中井筒内流态、压力、温度变化的准确认识,无法判断清井诱喷关键参数设计是否合理。为此,基于所建立的井筒多相流瞬态流动模型,以实际深水测试气井为研究对象,进行清井诱喷瞬态数值仿真模拟,真实再现实际工况下井筒内驱替工作液流动情况,量化清井诱喷过程中沿程压力、温度剖面非稳态变化,并对清井诱喷关键参数进行敏感性分析。研究结果表明:(1)模拟油压与实测油压的最大误差在±5%左右,拟合效果较好,验证了模型的准确性及可靠性;(2)清井时间随油嘴尺寸减小而递增;(3)诱喷液垫越高,气体从井底流出的初始速度越快,激动压力越大,清井诱喷时间越短;(4)在保障地面处理设备安全、平稳运行及经济有效的前提下,应尽可能采用大油嘴、大管径测试管柱并设定合理的诱喷液垫高度以完成清井诱喷。结论认为,该研究成果成功实现了深水气井测试清井放喷瞬态流动过程的模拟,对测试工作制度、测试管柱及设备的设计和选型,保证深水测试安全等都具有指导意义。

Transient flow simulation on the induced flow in well cleaning during deepwater gas well tests

The change of flow pattern, pressure and temperature inside the wellbore in the actual process of blowout is not understood accurately, so it is unable to judge whether the key parameters of induced flow in well cleanup during deepwater gas well test are designed rationally. In this paper, the testing of an actual gas well was taken as the research object. Based on the transient flow model of wellbore multiphase flow, transient numerical simulation was conducted on the induced flow in well cleanup to truly reproduce the flowing situation of displacement fluid in the borehole under the actual operating condition. The unsteady-state change of pressure and temperature profiles along the depth in the process of induced flow in well cleanup was quantified. Besides, sensitivity analysis was performed on the key parameters of induced flow. And the following research results were obtained. First, the maximum error between the simulated tubing pressure and the measured value is about ±5%, which indicates good fitting. It is verified that the model is accurate and reliable. Second, the cleanup time increases with the decrease of choke size. Third, the higher the flow inducing liquid cushion is, the faster the gas initially flows out of the bottom hole, the higher the excitation pressure is and the shorter the cleanup time is. Fourth, the induced flow in well cleanup shall be supplied with large choke, large-diameter test string and rational liquid cushion height as much as possible while ground treatment equipments are kept safe, smooth, economical and effective. In conclusion, these research results promote the successful simulation on the transient flow process of induced flow in well cleanup during deepwater gas well tests, and they can be used as a guidance for the formulation of testing system, the design and type selection of test strings and equipments and the guarantee of deepwater testing safety.