冰阀式保压取样器中冰阀形成数值模拟与试验

Numerical simulation and experimental studies on the formation process of ice valves for an ice-valve-based pressure corer

摘要:

保压取芯技术是天然气水合物调查研究必备的关键技术.为了克服现有保压取芯器在应用中保压成功率低的问题，提出了采用天然气水合物钻井液在原位生成冰阀代替机械阀门实现对水合物岩芯保压的冰阀式保压取芯器.采用设计的冰阀实验系统在实验室内对天然气水合物钻井液原位形成冰阀的过程与冰阀的密封承压能力进行了研究分析，并结合计算流体动力学技术对冰阀形成过程进行了仿真模拟.承压试验结果表明：冰阀的承压能力随冰阀长度的增长而增大；模拟结果与试验结果均表明随着冰阀长度的增长，冰阀形成所需时间也有所增长.因此，在满足地层保压取芯要求的前提下，应尽量采用较短的冰阀，以缩短冰阀式保压取芯器内冰阀的形成时间.

Abstract:

Pressure coring is considered as one of the key techniques for the natural gas hydrate-bearing sediment coring. To overcome the problem of low successful rate of pressure coring for a pressure corer, an ice-valve-based pressure corer made out of in situ drilling fluid during coring was proposed. A series of experimental tests were conducted by using a specially designed experimental system. The formation process of the drilling fluid ice valves was studied by both experimental tests and computational fluid dynamics (CFD) simulation method. The pressure sustaining capacity of the ice valves was also measured experimentally. Results showed that the sustained pressure of the ice valve increased almost linearly with the increase of the ice valve length. However, the increasing length of the ice valve caused the extension of formation time of the ice valve. To save the coring time, the ice valve length for pressure coring should be as short as possible while satisfying the sealing requirement.