An Integrated Technology of Continuous Foam Drainage in Gas Wells Based on Online Monitoring and Intelligent Decision System

Water production in gas wells is very complex in Daqing Oilfield on account of the volcanic reservoirs. Foam drainage is the most widely used dewatering technology. However, as to the conventional foaming, it is also known that manual workload is heavy and the accuracy and the timeliness of foaming agent injection are not effective, due to the influence of bad weather, scattered distribution of the remote wells and lack of in-time adjustment of agent injection rules. In order to solve these problems, an integrated foam drainage technology was developed to ensure intelligent, unattended, accurate and continuous foam dewatering. The integrated technology mainly consists of an online monitoring system, in which an automatic liquid level monitor and a gas-liquid two-phase flow monitor were invented, an intelligent controlling system, composed of specially developed hardwares and embedded intelligent decision softwares, and an automatic foaming agent injection device. Based on online monitoring of downhole liquid level and wellhead production parameters, such as tubing and casing pressures, gas and water production rates etc., the intelligent controlling system can quantitatively analyze the downhole loading liquid and production change, optimize the rules of foaming agent injection in real time, without human intervention. A pilot field trial was then taken, using the technology. The result showed the whole system operated normally. The average tubing-casing pressure difference reduced from 3.1 MPa to 0.4 MPa, the average production rate per day increased 1.1 × 104 m3. Compared with the conventional manual foam drainage technology, the foaming agent usage reduced 25%, the maintenance workload over 70%, which testified the new technology was feasible and highly effective. Therefore, it is of great significance for intelligent and digital liquid unloading in gas wells.