Modelling of 4D Seismic Data for the Monitoring of the Steam Chamber Growth During SAGD Process

Abstract

This paper presents an integrated workflow dedicated to the interpretation of 4D seismic data to monitor the steam chamber growth during the Steam-Assisted Gravity Drainage recovery process (SAGD). Superimposed to the reservoir heterogeneities of geological origin, many factors interact during thermal production of heavy oil and bitumen reservoirs, which complicates the interpretation of 4D seismic data: changes in oil viscosity, fluid saturations, pore pressure, etc.The workflow is based on the generation of a geological model inspired from a real field case of the McMurray Fm in the Athabasca region (Canada). The approach consists of three steps: 1/ the construction of an initial static model, 2/ the simulation of the thermal production of heavy oil with two coupled fluid-flow and geomechanical models, 3/ the production of synthetic seismic maps at different steps of steam injection.The distribution of geological facies is simulated on a very fine grid using a geostatistical approach which honours all available well data. The reservoir, geomechanical and elastic properties are characterized from logs and literature at an initial stage before the start of production. Production scenarios are run to obtain pore pressure, temperature, steam and oil saturations on a detailed reservoir grid around a well pair at several steps of production. Direct coupling with a geomechanical model leads to volumetric strain and mean effective stress maps as additional properties. These physical parameters are used to compute new seismic velocities and density for each step of production according to Hertz and Gassmann formulas. Reflectivity is then computed, and a new synthetic seismic image of the reservoir is generated for each step of production.The impacts of heterogeneities, production conditions and reservoir properties are evaluated for several simulation scenarios from the beginning of steam injection to three years of production. Results show that short-term seismic monitoring 2 can help in anticipating early changes in steam injection strategy. In return, long-term periods allow monitoring the behaviour of the steam chamber laterally and in the upper part of the reservoir. This study demonstrates the added value of 4D seismic data in the context of steam-assisted heavy oil production.

Analysis of Heavy Oil Recovery by Thermal EOR in a Meander Belt: From Geological to Reservoir Modeling

“…Many of these studies investigate stratigraphic architecture (sand and shale body dimensions and distribution) and reservoir connectivity and heterogeneity assessment at the reservoir scale (Richardson et al, 1978). Other studies focused on the potential effect on fluid flow of internal sand bodies and shale heterogeneities (Hartkamp-Bakker and Donselaar, 1993;Lerat et al, 2010).…”

“…The upscaling was performed using CobraFlow ™ while the SAGD reservoir simulations were performed using PumaFlow ™ . The results were analysed to see if the upscaling factor influences the description of the heterogeneities, a central issue in SAGD production (Birell and Putnam, 2000;Robinson et al, 2005, Zhang et al, 2005Chen et al, 2007;Lerat et al, 2010).…”

Simultaneous Inversion of Production Data and Seismic Attributes: Application to a Synthetic SAGD Produced Field Case

“…1). Following the work of Lerat et al (2010), a thermal fluid flow simulation was performed at this fine scale, thus resulting in reference production responses. Note that the resulting simulated behavior was pretty close to the one observed for the real field.…”

“…Thus, we tried to go one step further and determined the seismic traces from the convolution of a seismic wavelet with the reflectivity coefficients (Lerat et al, 2010). At this point, we considered the previously estimated P-wave impedance grids as unknown and the seismic traces as real seismic data.…”

“…Then, we build a synthetic, but realistic case defined from a real bitumen field (Lerat et al, 2010) produced from Steam Assisted Gravity Drainage (SAGD). It is used in the last section to illustrate the applicability of the proposed joint inversion approach.…”