Reservoir monitoring of steam‐assisted gravity drainage using borehole measurements

Abstract

This paper presents the results from a research project focusing on permanent cross‐well geophysical methods for reservoir monitoring during steam‐assisted gravity drainage. A feasibility study indicated detectable differences in seismic and electrical reservoir properties based on expected changes in temperature and fluid saturation during the production of extra heavy oil. As a result of this, a permanent cross‐well system was installed at the Leismer Demonstration Area, located in the Athabasca Oil Sands region in Alberta, Canada. Baseline data sets, including cross‐well seismic, three‐dimensional vertical seismic profiling and cross‐well electrical resistivity tomography, have been acquired. Comparisons between conventional surface seismic and downhole seismic data show an increase in resolution and frequency content as expected. Steam‐assisted gravity drainage‐induced time‐lapse effects are clearly visible in the 3D vertical seismic profiling and electrical resistivity tomography data sets, even after a few months of oil production. In general, the 3D vertical seismic profiling images show a higher resolution than the surface seismic data, in particular when dealing with vertical positioning of the time‐lapse events. The electrical resistivity tomography baseline shows clear separation between zones of high and low electrical resistivity, and during 23 months of electrical resistivity tomography measurements the maximum reduction of resistivity is 85%. Time‐lapse observations from acoustic and electrical borehole data correspond well, and are also supported by temperature measurements in the two observation wells. Emerging technologies, updated models, improved flexibility, and reduced costs will allow future reservoir monitoring with surface and borehole data in combination, or even with borehole data exclusively.

Fluid injection monitoring using electrical resistivity tomography — five years of injection at Ketzin, Germany

“…) and reservoir exploitation at intermediate depths (Tøndel et al . ), only a few examples exist on the application of ERT to CO 2 storage monitoring. This is due to the relative novelty of research dealing with the geological storage of CO 2 and the limited number of CO 2 storage sites where practical assessment of ERT is possible, namely, the Cranfield site (Carrigan et al .…”

Intra‐survey reservoir fluctuations – implications for quantitative 4D seismic analysis

“…A further possibility involves the use of time‐lapse (3D) Vertical Seismic Profile (VSP) to provide highly accurate images over a small image area (Tøndel et al . ; Pevzner, Urosevic and Gurevich ).…”

A land-based controlled-source electromagnetic method for oil field exploration: An example from the Schoonebeek oil field

“…However, reservoir simulation data suggest (Streich, 2016) that areas of increasing as well as decreasing resistivity are expected at Schoonebeek due to simultaneously ongoing processes of different magnitudes, lengths, and timescales. Temperature increase, gradual condensation of steam, displacement of highly resistive oil, as well as the reduction of salt concentration due to the mixing of steam with saline water are some of the processes that may lead to compartmentalization of the reservoir with different zones showing increasing and decreasing resistivity, respectively (Tøndel et al, 2014). Thus, 3D inversion of the EM data is needed.…”