Fresh Water Hydration and Wetting/Flooding Experiments on Cardium Formation Arenites, Wackes and Mudstones Using an Environmental-Field Emission-Scanning Electron Microscope (E-FE-SEM)

Abstract

Rapid application of horizontal drilling and completions technology in previously uneconomic zones or halos of existing Cardium Formation reservoirs developed more quickly than our understanding of the rock quality of these reservoir intervals. To reduce this gap in knowledge we are studying the formation along the halo of the Pembina Field. These rocks were previously described as non-reservoir and as consequence were less studied. For the past 60 years fresh water floods have been used for repressurization purposes in vertically drilled portions of the Pembina Field. While repressurization has achieved the intended purpose, rapid declines in oil production were noted in many areas when water floods contacted oil-producing wells. Furthermore, completion practices of horizontal wells have shown that base fluids used during fracking have a strong influence on the first year of oil production. Significant declines in production also result when neighboring horizontal wells are fracked and fracking fluids comingle with fluids from producing wells. With the E-FE-SEM in the Department of Geoscience, University of Calgary, we are conducting two types of experiments to study the effects of fresh water on halo-play rocks. In the first group, water is allowed to first condense on the rock surfaces and then evaporate from them. In the second group of experiments, the microscope's sample chamber is saturated with water vapour, but below the threshold of condensation. Here the rock sample is left to absorb the water for a defined period of time and then imaged at fixed intervals from the start to the finish of the experiment. Throughout active saturation experiments continuous release and separation of fines from the rock surface was observed. Individually and in clusters all kinds of minerals grains are displaced and move with advancing water. In areas that contain masses of swelling clays these materials bulk up, expand and extrude from the sample. Passive hydration experiments, while not as dramatic as the active saturation experiments, illustrate clearly that swelling minerals expand and that they progressively modify rock surfaces and visible pores. These experiments show that clear understanding of the geology in the subsurface can be a critical determinant in effective and efficient reservoir production.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016