Multi‐dimensional analyses of the SEAM controlled source electromagnetic data—the story of a blind test of interpretation workflows

Abstract

A B S T R A C TUsing a subset of the SEG Advanced Modeling Program Phase I controlled-source electromagnetic data, we apply our standard controlled-source electromagnetic interpretation workflows to delineate a simulated hydrocarbon reservoir. Experience learned from characterizing such a complicated model offers us an opportunity to refine our workflows to achieve better interpretation quality. The exercise proceeded in a blind test style, where the interpreting geophysicists did not know the true resistivity model until the end of the project. Rather, the interpreters were provided a traditional controlled-source electromagnetic data package, including electric field measurements, interpreted seismic horizons, and well log data. Based on petrophysical analysis, a background resistivity model was established first. Then, the interpreters started with feasibility studies to establish the recoverability of the prospect and carefully stepped through 1D, 2.5D, and 3D inversions with seismic and well log data integrated at each stage. A high-resistivity zone is identified with 1D analysis and further characterized with 2.5D inversions. Its lateral distribution is confirmed with a 3D anisotropic inversion. The importance of integrating all available geophysical and petrophysical data to derive more accurate interpretation is demonstrated.

Controlled-source electromagnetic and seismic delineation of subseafloor fluid flow structures in a gas hydrate province, offshore Norway

“…Such non-uniqueness may lead to interpretation ambiguity that can be mitigated adequately by integrating all available geophysical data for the purpose of forward, inverse and synthetic modelling (Tseng et al 2015). Our 2.5D CSEM inversions were proven to be effective in detecting resistivity anomalies in the pockmark region.…”

“…In synthetic model studies where the true model is known, the inversion algorithms and survey parameters can be examined for their capability to resolve the true EM structure Tseng et al 2015). To produce reliable synthetic models, pragmatically it is advisable to introduce simple structures within a homogenous host .…”

Marlim R3D: a realistic model for CSEM simulations - phase I: model building

“…Most of the available models are simple physical models with a known mathematical formulation. These models are suitable for software development, but they are inefficient to represent the geological complexity of the marine substrate adequately and, hence, tend to negatively impact the workflow of real data interpretation in the hydrocarbon exploration industry (Tseng et al 2015).…”

“…Thus, it can be used for seismic, gravimetric and electromagnetic stand-alone or joint simulations. Since its implementation, SEAM-1 has been used by the oil companies in-house simulations, and also in the academy (Tseng et al 2015).…”

Comparing large-scale 3D Gauss–Newton and BFGS CSEM inversions

“…To our knowledge, studies using Hessian/Gauss-Newton tools on full-scale 3D CSEM data sets have not been published. 2.5-dimensional Gauss-Newton inversion implementations have provided very good inversion results when the geology is close to 2dimensional, examples are Hansen and Mittet (2009); Key (2012); Tseng et al (2015); Wiik et al (2015).…”