定向穿越管道的挤毁失效及其防护装置的设计

Collapse failure of directional crossing pipelines and the design of its protective devices

定向穿越敷管技术由于其特殊优势,被越来越多地应用于油气管道敷设,但复杂的地质条件又极易导致穿越管道挤毁失效,对油气输送安全造成严重威胁。为此,针对复杂地层中穿越管道的挤毁失效行为,分析了其失效原因,主要是由孔壁失稳、地层沉降和地下水渗流等所导致的。进而基于管材非线性及管土耦合作用,建立了无缺陷和凹陷穿越管道的挤毁数值计算模型,并对其挤毁行为进行了研究。结果表明:①无缺陷管道与凹陷管道的挤毁失效模式不同,完整穿越管道的挤毁过程可分为6个阶段,管道横截面经历了椭圆形、"新月"形、"葫芦"形及"8"字形变化过程;②而凹陷管道的挤毁过程可分为5个阶段,管道横截面经历了"心"形、"新月"形、"葫芦"形及"8"字形变化过程;③围土压力越大,管道的挤毁失效后果越严重。最后,设计了一种结构简单、易于操作且具有自主知识产权的定向穿越管道用防护装置,可以有效降低管道发生凹陷、挤毁等失效的概率,延长管道使用寿命,可用于穿越危险地层的油气管道防护。

Directional crossing pipeline laying technology is applied to more and more oil and gas pipelines in virtue of its unique advantages, but the crossing pipelines tend to be collapsed to failure because of complex geologic conditions, so the safety of oil and gas transportation can not be guaranteed. In this paper, therefore, analysis was conducted on the collapse failure behaviors of crossing pipelines in complex formations to find out the failure reasons （mainly borehole wall instability, formation subsidence and under- ground water seepage）. And on the basis of pipeline nonlinearity and pipe-clay coupling, collapse numerical computation models for zero defect and dent crossing pipelines were established to study the collapse behaviors. It is shown that collapse failure model for ze ro defect pipelines is different from that for dent pipelines. The whole collapse process of cross pipelines is divided into six stages and the cross sections of the pipelines experience the change in the shapes of ellipse, crescent, calabash and ＂8＂. That of dent pipelines is divided into five stages and the cross sections present successively the shapes of heart, crescent, calabash and ＂8＂. The higher the surrounding earth pressure is, the more seriously the pipelines are collapsed to fail. In this paper, protective devices for directional cross pipelines are designed with independent intellectual property right and they are simple in structures and flexible in operation. The protective devices can effectively decrease dent frequency and failure （e.g. collapse） probability of pipelines and prolong their service life. They can be used to protect oil and gas pipelines that run through danger beds.