Session 1 - Oral 13
Study on Throttling Characteristics of Hydraulic Cylinder throttle Valve and Control Strategies for MPD
Hao Shen1, Hao Li1, Baojiang Sun1*, Xuerui Wang1, Chengzhen Shi1, Meipeng Ren2, Zhiming Yin2
1 Key Laboratory of Unconventional Oil and Gas Development, Ministry of Education, China University of Petroleum (East China), Qingdao 266580, China;
2CNOOC Research Institute Company Limited, Beijing 100028, China
Abstract: The surface choke manifold is the core part of the Managed Pressure Drilling system, on which the adjustment of the throttle valve components is very important for exquisite control of the pressure in the wellbore. Whereas there are still few field experiments of hydraulic throttle valve under gas-liquid two-phase flow, of which lack significance for field guidance, so it is necessary to conduct further study in this area. By building a field full-scale experimental platform, taking drilling fluid as the experimental object, and using a new cylindrical throttle valve, the pure liquid phase and gas-liquid two-phase flows experiments were carried out respectively. Taking into account the pressure bearing capacity of the experimental system, the throttle valve’s opening adjustment ranged from 19%-100% in the experiment. The experimental results showed that the new cylinder throttle valve had a good linearity when the opening was lower than 40%, and its invalid opening interval was 80-100%. During the pure liquid phase flow experiment, when the drilling fluid displacement was changed from 15L/s to 20L/s, the choke pressure varied from 0.5MPa to 7.3 MPa. When the opening was less than 40%, the choke pressure changed rapidly, the smallest opening unit was recommended while operating and when the opening was between 40% and 80%, the choke pressure did not change significantly, the opening unit could be changed based on actual needs while operating and the choke pressure was basically unchanged when the opening was between 80% and 100%, in which it was suggested that the operation of the valve be avoided. Under the gas-liquid two-phase flow experiment, the initial void fraction was changed from 0.3321 to 0.4484, the drilling fluid displacement was changed from 15L/s to 20L/s, the choke pressure ranged from 1.09-9.7MPa, and when the initial void fraction reached at the maximum of 0.4484, under the same opening and liquid phase displacement, the choke pressure was the largest, and the other laws showed were basically the same as those under the experiment of pure liquid phase flow. By comparing the curves of choke pressure with opening in pure liquid phase and gas-liquid two-phase, it was found that the choke pressure in gas-liquid two-phase was larger under the same liquid displacement and the same opening, which conformed to the law. In addition, considering the gas disturbance, it was suggested to slow down the operation of the valve in gas-liquid two-phase flow. The throttling characteristic experiments of pure liquid and gas-liquid two-phase flows of the hydraulic cylinder throttle valve are good references for the Managed Pressure Drilling in field, and meaningful for guidance.
Keywords: cylinder throttle valve; throttling characteristics; field experiment; managed pressure drilling; gas-liquid two-phase flow