Knowledge of the electrical resistivity of the subsurface has a wide range of applications in the oil and gas, mining, and geothermal industries. The resistivity distribution can be used as a direct indicator of the presence of hydrocarbons or for delineation of structural features and lithological changes at a basin or regional scale (e.g., the shape of salt bodies, basalt thickness, basement depth and geometry). Mining and geothermal uses of resistivity are for localizing potential targets of ore bodies and geothermal reservoirs, respectively.

Omega 3D Electromagnetic Modeling is used to infer the anisotropic resistivity distribution of the subsurface through 3D inversion of controlled-source electromagnetic (CSEM) and magnetotelluric (MT) data. CSEM and MT synthetic responses of the subsurface can be computed starting from the resistivity distribution (i.e., forward modeling).

Omega 3D Electromagnetic Modeling is a parallel application available as a Seismic Function Module (SFM) of the Omega geophysical data processing platform or independently as a stand-alone application. It requires a high-performance computing (HPC) system to run.

WORKFLOW

The efficient Omega 3D Electromagnetic Modeling workflow maximizes geophysicist productivity. 

  • Model building and parametrization of the modeling and inversion are completely performed in the Petrel CSEM plug-in or the Petrel Magnetotellurics plug-in.
  • Setup and submission of the job in the Omega platform are effortless, and the subsequent job execution and monitoring leverage the tools available in the Omega platform.
  • Evaluation and the QC of results are performed in the Petrel platform with unparalleled usability: The imported results are automatically dispatched on the Petrel platform tree, preserving the relationship among data, models, and job parameters and granting fully traceable and repeatable workflows. 

ON-DEMAND SERVICES

  • Omega 3D Electromagnetic Modeling can also be accessed through an on-demand (pay-per-use) model with Schlumberger geoscientist support.
  • The user licenses the Petrel CSEM or Petrel MT plug-in and uses it to create and export a job archive. During the parameterization of the job, the user is assisted by a dedicated Schlumberger geoscientist.
  • The job archive is transferred by the user to Schlumberger through a secure data exchange connection.
  • Schlumberger submits and executes the transferred job on an HPC system and sends the results to the user as soon as they are available.
  • The results are packaged into an archive that is seamlessly loaded into the Petrel platform.

The user evaluates the results using the Petrel CSEM or Petrel MT plug-in, again with Schlumberger assistance if required.

Applications

  • Assessment of hydrocarbon presence and accumulation
  • Delineation of complex geological features that challenge seismic imaging (e.g., subsalt, sub-basalt)
  • Characterization of geothermal reservoirs
  • Localization of mining targets

Features

  • The computational engine for the 3D MT forward modeling and inversion has been in commercial use since 2000 and the engine for the 3D CSEM forward modeling and inversion has been commercial since 2006. Overall, the two applications have been used for the modeling and inversion of more than 2,000 datasets and are continuously upgraded to enhance results and optimize performance.
  • The formulations of both the MT and CSEM problems support isotropic and anisotropic resistivity models, and the anisotropy formulation can be either vertical transverse isotropic (VTI) or diagonal.
  • The CSEM engine is multifrequency, so it can model the true position of both the electromagnetic source and receivers, electric and magnetic channels, and inline and offline soundings.
  • The MT engine can model the full tensor and the tipper.
  • The formulation of the inverse problem enables including several kinds of geologically or seismically driven constraints (e.g., weighted penalization, regularization breaks, a priori models).
  • Scalability means that the application can easily handle both sparse 3D land datasets and large and dense 3D marine surveys.
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