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Understanding Frost Heave Induced Crude Oil Pipeline Failure in Permafrost Zone Through the Simulation of Moistured Clay Soil Frost Formation Process

Festus Owu^1*

Abstract

The importance of meeting the energy needs of man cannot be overemphasized. One means of satisfying this need is through crude oil supply via pipeline network systems. The hazards inherent with crude oil pipeline failure is devastating, even as its cause is traceable to both human and natural activities. One of the natural causes of pipeline failure is due to the effect of extreme cold weather leading to the formation of frost heave that exert upward thrust on buried pipeline, thereby causing a deformation of the pipeline structure which eventually culminate to operational failure. In this study, a simulation of one-dimensional moist clay frost formation process is carried out through the use of the finite difference (backward) scheme in the analysis of the heat conduction governing equation of the moist clay to determine the nodal temperatures with respect to an imposed sub – zero temperature. The nodal heave displacement of the analyzed sample is there after determined based on the knowledge of the nodal temperatures through the analysis of the heave rate governing equation using also the finite difference approximation method. It is shown that at a prevailing -10℃ imposed top soil temperature, that in 7.3hours (22 numbers of time steps of 20-minute time step), that the last node which is the node of interest considering its closeness to the most frequently used burial depth of crude oil pipeline (1.6m) recorded no significant temperature drop (20℃ drops to 19.99935℃), with zero heave displacement. However, in five days (360-time steps) of the sustained imposed temperature, the heave displacement grew to 89.02mm (0.08903m). This result shows that frost heave formation is possible in the entire profile for a prolonged period even if the profile extends to and beyond the burial depth of pipelines. This outcome therefore suggests the need for a geotechnical survey of soils on possible path ways of pipelines for adequate soil treatment and the selection of proper pipes to withstand the predetermined stresses in order to prevent the catastrophes associated with frost induced pipeline operational failures.

Keywords:

Frost heave: Finite difference: Simulation: Soil profile: Nodal temperatures: Phase change algorithm