Subsurface characterization and geological monitoring of the CO ₂ injection operation at Weyburn, Saskatchewan, Canada

Abstract

Abstract:The IEA Weyburn Carbon Dioxide (CO 2 ) Monitoring and Storage Project analysed the effects of a miscible CO 2 flood into a Lower Carboniferous carbonate reservoir rock at an onshore Canadian oilfield. Anthropogenic CO 2 is being injected as part of a commercial enhanced oil recovery operation. Much of the research performed in Europe as part of an international monitoring project was aimed at analysing the long-term migration pathways of CO 2 and the effects of CO 2 on the hydrochemical and mineralogical properties of the reservoir rock. The pre-CO 2 injection hydrochemical, hydrogeological and petrographical conditions in the reservoir were investigated in order to recognise changes caused by the CO 2 flood and to assess the long-term fate of the injected CO 2 . The Lower Carboniferous (Mississippian) aquifer has a salinity gradient in the Weyburn area, where flows are oriented southwest-northeast. Hydrogeological modelling indicates that dissolved CO 2 would migrate from Weyburn in an east-northeast direction at a rate of about 0.2 m/year under the influence of regional groundwater flow. The baseline gas fluxes and CO 2 concentrations in groundwater were also investigated. The gas dissolved in the reservoir waters allowed potential transport pathways to be identified. Analysis of reservoir fluids proved that dissolved CO 2 and methane (CH 4 ) increased significantly in the injection area between 2002 and 2003. Most of the injected CO 2 exists in a supercritical state, lesser amounts are trapped in solution and there is little apparent mineral trapping. The CO 2 has already reacted with the reservoir rock sufficiently to mask some of the strontium isotope signature caused by 40 years of water flooding. Experimental studies of CO 2 -porewater-rock interactions in the Midale Marly Unit indicated slight dissolution of carbonate and silicate minerals, followed by relatively rapid saturation with respect to carbonate minerals. Carbon dioxide flooding experiments on similar samples demonstrated that porosity and gas permeability increased significantly through dissolution of calcite and dolomite. Several microseismic events were recorded over a six-month period and these are provisionally interpreted as being related to small fractures formed by injection-driven fluid migration within the reservoir, as well as other oilfield operations. Experimental studies on the overlying and underlying units show similar reaction processes, however secondary gypsum precipitation was also observed. Reaction experiments were conducted with CO 2 and borehole cements. The size and tensile strength of the cement blocks were unaffected, however their densities increased. A multidisciplinary study of the till deposits in the Weyburn area indicates that a single, heterogeneous till sheet is present. Pre-and post-injection soil gas data are consistent with a shallow biological origin for the measured CO 2 in soil gases. Isotopic (δ 13 C) data values are higher than in the injected CO 2 , and confirm this interpretation. No evidenc...

Hydrogeological challenges in a low-carbon economy

“…Indeed, injection of CO 2 itself into deep strata has already been practised for many years for purposes of sour gas disposal and/or enhanced hydrocarbon recovery, at several localities both offshore (at Sleipner, in the Norwegian North Sea; Zweigel et al 2004) and onshore (e.g. at In Salah (Algeria), where injection occurred from 2004 to 2011 without leakage to the surface (Mathieson et al 2010), and at Weyburn (Canada), where many advances in CCS monitoring technologies have been made (Riding & Rochelle 2009).…”

Comparison of surface and near-surface geochemical methods for detection of gas microseepage from carbon dioxide sequestration

“…Radon-222 also has the longest half-life, 3.82 days. Although a tracer with a half-life of 3.82 days is not adequate to be derived from a sequestration reservoir, it can be swept up from shallow depths by migrating gases from greater depth ("carrier gas;" Klusman, 1993Klusman, , 2009Riding and Rochelle, 2009). Radon is easily measured by simple instrumentation and can serve as a surrogate tracer for locating an upward gaseous flow from greater depths.…”

“…• Gas chromatographic measurement of He, Ne, and Ar with the appropriate detector; Xe and Kr concentrations are too low for gas chromatographic measurement, but could be determined by mass spectrometry (commercial literature), • A laboratory measurement, but could be done in a field laboratory on the project site, • Rn is a simple, low-cost measurement, amenable to continuous field measurement, and could possibly serve as an indigenous tracer for higher concentration gases migrating from deeper sources (Rose et al, 1988;Klusman, 1993Klusman, , 2009Riding and Rochelle, 2009). …”

Hydrogeological and Geomechanical Aspects of Underground Coal Gasification and its Direct Coupling to Carbon Capture and Storage

“…Weyburn, Saskatchewan; Riding and Rochelle 2009) and offshore (Sleipner, Norwegian North Sea; Chadwick et al 2009). Micro-seismic, micro-gravity, and electromagnetic monitoring techniques appear to be amongst the most promising approaches (Chadwick et al 2009), which (at least in onshore settings) can be backed up with surface monitoring of CO 2 (Riding and Rochelle 2009).…”