Updating the low-frequency model in time-lapse seismic inversion: A case study from a heavy-oil steam-injection project

Abstract

A workflow to update the time-lapse low-frequency model in a data-driven manner in time-lapse inversion studies is applied to a heavy-oil reservoir produced using the steamassisted gravity drainage (SAGD) method. The base seismic survey and the difference between the base and monitor surveys are inverted in two separate inversion runs, and no assumptions are made regarding the reservoir changes or the relationships between elastic or reservoir parameters. The effects of production are estimated from the inversion of the difference between the base and monitor surveys. This information is used to update the low-frequency model in the time-lapse sense. A good match can be observed between the inversion results and other available information from the field, confirming the validity of the method.

Bayesian stochastic inversion with petro-elastic relation to quantify thin gas sands of Khadro Formation, Zamzama gas field

“…The LFMs assimilate the low pass filtered information to the inversion algorithm and contribute to obtaining broad-band absolute information instead of relative (Oyedele et al, 2020;Imran et al, 2022). The PEMs modeled elastic logs result in enhanced LFMs that capture more accurately the reservoir properties on inverted attributes due to well-prepared and corrected logs (Mesdag et al, 2015). The prior models are converted into a stratigraphic grid of 0.1 ms cell size, considering the accurate population of information according to the thinness of potential sands.…”

Quantitative inversion of azimuthal anisotropy parameters from isotropic techniques

“…Instead of choosing a negative branch for V P /V S and getting only negative anisotropy numbers, employing a prior azimuth leads to a two-sided signal for the Fourier coefficient b 1 . Since this anisotropy signal is a calibrated band-limited representation of the full bandwidth b 1 , it can be used to reconstruct the full-bandwidth signal from its peak-to-trough amplitudes which correspond to relative contrasts (Mesdag et al, 2010(Mesdag et al, , 2015. Such contrast in azimuth and b 1 are enough to build an azimuthal low-frequency model using the following approximation (Zhang and Mesdag, 2016):…”

Time-lapse rock-physics inversion of thermal heavy oil production

“…Previous 4D AVO inversion studies associated with bitumen saturated reservoirs by Mesdag et al (2015) and Gray et al (2015), either invert the seismic differences or invert the baseline and monitor surveys separately to create difference volumes for the elastic properties. A shortcoming of this formulation is that it can introduce 4D changes due to noise differences between seismic vintages.…”

“…Mesdag et al (2015) applied a simple, linear interpolation on inversion results between interpretations for top and bottom of steam chamber to create 4D low frequency models for AI andVp/Vs. The drawbacks to such a methodology are 1) interpretation of top and bottom of steam chamber is time consuming and subjective in nature; and 2) this method allows only for linear variation and does not account for potential layering of events such as heated oil lying both above and below the steam chamber as the SAGD process predicts.…”