温压荷载作用下深部原位保压取心控制器承压特性研究

Pressure-bearing characteristics of pressure-preserved controllers under deep in-situ temperature and pressure conditions

深部原位保压取心是深部流态资源(煤层气、页岩气等)储量评估的重要途径,其密封性能与承压能力受温压影响显著。然而目前研究鲜有考虑深部原位环境(温度、压力)对保压控制器极限耐压能力与保压效果的影响。围绕保压控制器在深部环境下承压性能关键问题开展研究,进行保压控制器运动分析,开展304钢高温拉伸实验,获取其材料力学特性。基于自主研发的保压取心实验室模拟测试平台与数值仿真研究手段,模拟深部原位环境下保压控制器结构变形与应力分布特征,提出保压控制器失效控制策略。结果表明:(1)随着温度增加,304钢的屈服强度呈降低趋势,25、50、100、150、200℃条件下,其平均屈服强度分别约为556.42、536.26、513.22、511.00、489.88 MPa;(2)其失效内因在于阀盖等效应力集中于底面中部,阀盖结构变形以短轴两翼向内部收缩为主,导致密封接触压强降低,无法形成有效密封;(3)为了提高保压控制器的承压性能,建议通过优化材料性能(选取弹性模量大的材料)来降低保压控制器的变形,或在阀座内置限位结构来控制阀盖弱侧变形,促使保压控制器处于“越压越紧”的良性状态。相关研究可为深部原位保压取心控制器结构优化与能力增强提供借鉴。

Deep in-situ pressure-preserved coring is an important method for the reserves evaluation of deep flow resources,such as coalbed methane and shale gas.The sealing performance and pressure-bearing capacity during the coring are significantly affected by temperature and pressure.However,existing studies scarcely incorporate the influence of the deep in-situ environment(i.e.,temperature and pressure)on the ultimate pressure-bearing capacity and pressurepreserved effects of pressure-preserved controllers(PRCs).Focusing on the key issues related to the pressure-bearing performance of PRCs in a deep environment,this study conducted a kinematic analysis of PRCs.This study also performed high-temperature tensile tests of 304 stainless steel,determining its mechanical properties.Based on the self-developed laboratory simulation test platform and numerical simulation methods for pressure-preserved coring,this study obtained the structural deformations and stress distribution of PRCs under the simulated deep in-situ environment.Accordingly,this study proposed a failure control strategy for PRCs.The results are as follows:(1)The yield strength of 304 stainless steel showed a downward trend as the temperature increased.Its average values were 556.42 MPa,536.26 MPa,513.22 MPa,511.00 MPa,and 489.88 MPa at 25℃,50℃,100℃,150℃,and 200℃,respectively.(2)The internal reason for PRC failure was determined.For the valve cover of a PRC,its equivalent stress was concentrated in the central part of its bottom,and its structural deformations were dominated by the contraction from both wings of its short axis toward its inside.As a result,the pressure intensity of the sealing contact reduced,making it difficult to form effective sealing.(3)To improve the pressure-bearing capacity of PRCs,it is recommended that material properties should be optimized(i.e.,by selecting materials with a high elastic modulus)to reduce the deformation of PRCs or that the deformations on the weak side of the valve cover should be controlled by installing a limit structure in the valve seat to make the PRCs become tighter under higher pressure.This study can be used as a reference for the structural optimization and capability enhancement of deep in-situ PRCs.