Monitoring SAGD Conformance and Caprock Integrity With Depth to Surface Resistivity
Traditional resistivity exploration techniques such as electrical resistivity tomography have long been used for characterizing oil sands in the upper 200 to 300 m. The resistivity contrasts between heavy oil saturated sands, clay or shale cap rocks, and saline basal aquifers offer excellent exploration targets, but due to the sensitivity limitation of measurements made from the surface, these traditional methods are not applicable to many SAGD projects. Depth to Surface Resistivity improves depth sensitivity by using well casing as a source. In this study we have modelled the electric field measured by an array of capacitively-coupled receivers along the surface. The electric field is generated by an electrical source coupled to the top or bottom of a well casing, which acts as a current pathway directly into the depth of interest. 3D inversion methods are used to ensure that the electrical resistivity model can be recovered from the measurements made at the surface. Using 3D numerical modeling tools that also include the effects of infrastructure we show the results from feasibility modeling for an SAGD oil sands project. This includes imaging the continuity of the caprock prior to or during steam injection, imaging the steam chamber evolution through its expected lifetime, and imaging local aquifers prior to and during steam injection.
AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016