Characteristics of Soil Under Variations In Clay Content And Overburden Pressure
Authors: Aikman M. , Kantzas A. , Mirotchnik K. , Marentette D.F. , Allsopp K. 
Published: March 2010

An investigation is underway at the University of Calgary/TIPM Laboratory to examine a potential in situ soil remediation process. The focus is intended to demonstrate the potential to adapt proven and economic petroleum engineering methods to soil remediation. Specific methods to be applied are envisioned to be water and gas displacement processes in conjunction with horizontal boreholes as the injection and production points. The potential application of this method is for such sites where soil excavation and treatment would be impossible. This would be the case for spills that seep beneath a plant or other immovable infrastructure.

The characterization of native soil samples, obtained from an industrial plant in central Alberta, has been completed using methods such as grain size analysis, microscopic visualization, X-Ray Diffraction (XRD), and capillary pressure determination. The data obtained from the characterization process was used to construct synthetic, representative synthetic soil specimens to use as test materials in laboratory experiments. The use of synthetic soils allows for parametric studies to be performed, as well as a generalization of various observations to other soil types that may fall in the range of the synthetic soil constructs.

In order to understand the impact of clay and overburden pressure upon the rock structure and fluid flow characteristics, various synthetic soils have been packed into conventional core analysis equipment. The parameters studied so far have been variations in clay content, and the overburden pressure. The impact of these variations upon the core characteristics such as porosity, and single phase flow permeability have been quantified, and are reported herein. The saturations of the various fluids have been investigated using packed columns and capillary pressure measurements. Implications of the results upon both the contaminant displacement process, and the laboratory equipment, are reported. Future work that is proposed for further investigation is outlined in brief.

Introduction

Hydrocarbon contamination of soil is a problem associated with various petroleum operations, from the well-head all the way downstream to the petroleum service stations. Other important areas where spillage of hydrocarbon occurs are at large tank farms, and in the refinery complex. It has been claimed(1) that there are, in Canada alone, some 100,000 sites with various degrees of contamination, and that remediation of such sites would require expenditures of some $ 20 billion. Thus, there is a large incentive to find economical and effective methods to remediate such sites. Furthermore, there are conventional methods of remediation that are in some instances impractical if not outright impossible. Should the spill have occurred underneath an area of existing infrastructure that cannot be readily "moved aside", in situ methods will be required in order to clean up the contaminant plume. In one recent field study(2), horizontal boreholes were utilized in order to access the spillage plume. The spillage plume had seeped underneath a major highway, and the governing authorities would not permit disruption to traffic flow on this piece of infrastructure. Other immovable objects also include buildings.