Coupling strategies in multiparameter geophysical joint inversion

Abstract

SUMMARY A big potential lies in the quantitative integration of multiple geophysical measurements for what concerns more unique and robust inversion results, complementary sensitivity to geological features and enhanced resolution. The mechanisms that enable such integration typically rely on statistics where the multiphysics parameter values are related to each other through regression functions (rock physics) or through the shape of the parameter spatial distributions (structure). Such coupling operators are jointly minimized with the data misfit to obtain coupled parameter distributions. We explore the application of various coupling mechanisms to synthetic and real data comprising seismic and electromagnetic measurements acquired in complex geological conditions such as salt geology and complex near surface in desert environment. Two types of structure operators, consisting of the standard cross-gradient and a newly introduced summative gradient, together with rock-physics operators are tested and combined for velocity model reconstruction of salt overburden in a marine environment and in a complex near surface case. Results of seismic-EM joint minimization suggest that the summative gradient operator with the introduction of the sign of the gradient correlation provides a strong coupling mechanism that can become advantageous in the presence of noise-affected seismic data. The rock-physics coupling mechanism is extremely strong and its effectiveness depends primarily on the reliability of the rock-physics relation. A Bayesian approach for the rock-physics operator is introduced to balance the related uncertainties and it is successfully tested in a joint minimization scheme. The combined use of rock-physics and structure coupling operators provides the best results in synthetic and real data applications. The use and combination of various regularization operators, as described, provide a formidable toolbox for solving a wide variety of ill-posed and non-unique geophysical inverse problems.

Joint inversion of seismic and electrical data in saturated porous media

“…An interesting review of joint inversion of seismic and electromagnetic data is provided by Moorkamp et al . (2016) and Colombo and Rovetta (2018). Among the hydrocarbon applications, one can find the scheme proposed by Gao et al .…”

“…Moreover, for uncemented coarse granular materials, common in the near surface, it is difficult to retrieve undisturbed samples without resorting to very expensive techniques, such as ground freezing (Singh et al ., 1982; Hofmann et al ., 2000) or gel‐push sampler (Mori & Sakai, 2016). The abovementioned relationships may also be used to constrain seismic and electrical models, in the perspective of joint inversion of different data to mitigate the non‐uniqueness of the solution as it is common in hydrocarbon exploration (Moorkamp et al ., 2016; Colombo & Rovetta, 2018).…”

“…Several examples of joint inversion are described in the literature, especially in the field of hydrocarbon exploration, where dedicated rock physics studies and characterization are carried out on the investigated formations and accurately calibrated empirical relationships among the geophysical parameters are available. An interesting review of joint inversion of seismic and electromagnetic data is provided by Moorkamp et al (2016) and Colombo and Rovetta (2018). Among the hydrocarbon applications, one can find the scheme proposed by Gao et al (2012), in which electromagnetic and seismic measurements are jointly inverted and the final model is solved for porosity and saturation degree, while the final geophysical parameter distributions, namely P-wave velocity and resistivity models, are calculated a posteriori.…”

Feature-Oriented Joint Time-Lapse Seismic and Electromagnetic History Matching Using Ensemble Methods

“…Joint inversion of multiple sources of geophysical data has been actively studied in the geophysical community [22,37,2,31,53,36,48,10], due to its great potential to enhance the fidelity of inverted models. The core idea of joint inversion is to exploit the complementary nature between different types of geophysical data sets, and combine the information into an integrated inversion scheme for better recovery of properties or structures within the reservoir.…”

Efficient Joint 4D Seismic and Electromagnetic History Matching Using an Ensemble-Based Approach

“…Joint inversion of multiple sources of geophysical data has been actively studied in geophysical community due to its great potential to enhance the fidelity of inverted models (Dell'Aversana et al, 2011;Moorkamp et al, 2011;Liang et al, 2016;Sun and Li, 2016;Colombo and Rovetta, 2018). The core idea of joint inversion is to exploit the complementary nature between different types of geophysical data sets and combine the information into one single inversion scheme for better recovery of properties or structures within the reservoir.…”