Thin layers of soft clay seam exist beneath the earth surface at several locations in Western Canada. They were formed out of volcanic eruptions in the past and were buried due to geological depositions on them from the top. Over the years, they have undergone several fabric and mineralogical transformations due to in situ pressure and existing physicochemical environment. Relative shearing of soil layers above and below a clay seam is always possible in the presence of a source of shearing. Several casing (meant for extracting oil) failures have been reported from the oil fields of Alberta due to such relative shearing of soil layers above and below the existing clay seam. At these sites, cyclic steam stimulation (a thermal process) technique is used to extract oil. In the mentioned technique, steam at high pressure and temperature is injected in oil bearing formations to reduce their viscosity before extraction, and it also acts as an excitation source of shearing along the clay seam. Beforehand knowledge of relative shear displacement along clay seam caused by a certain steam pressure can help reduce the number of casing failures. In the present work, an analytical elastic model has been developed to estimate the shear displacement along the clay seam due to steam injection. Concepts of elastic fracture mechanics were used to estimate the relative displacement. Several laboratory tests including creep test, direct shear box test, mineralogical and fabric analyses were conducted on samples of clay seam for their complete characterization.

Bibliography: p. 153-166