Azimuthal Imaging using Deep-directional Resistivity Measurements reveals 3D Reservoir Structure
by Michael Thiel, Schlumberger
was presented on the 6 th of March, 2019.
The reservoir scale deep-directional electromagnetic logging-while-drilling technology is now routinely being used to map boundaries and fluid contacts for strategic geosteering, reservoir navigation, and more recently, for reservoir characterization. Data interpretation is based on inversion algorithms that estimate a local resistivity profile and usually a 1D layered profile is continuously estimated during real-time interpretation. The traditional inversion approaches ignore the lateral changes of the reservoir, which are contained in the measurements, only a longitudinal 2D representation of the 3D reservoir structure around the well is provided. This limits the ability to make real-time geosteering decisions with respect to lateral reservoir heterogeneities, such as faults to the side of a horizontal well.
In this talk, an inversion is presented that can provide 2D azimuthal resistivity images in a plane transverse to the wellbore; thus, the inversion is able to map lateral reservoir heterogeneities. The minimally biased algorithm uses a nonuniform 2D pixel discretization of the imaging plane, initially perpendicular to the near-horizontal well. This algorithm takes advantage of the full 3D sensitivities of deep-directional resistivity measurements to map the 2D resistivity distribution. A fast EM simulator is used to reconstruct the tool response in complex 2D anisotropic formations for arbitrary tool orientation. Continuous azimuthal 2D imaging along the well path generates a 3D map of the reservoir in the proximity of the wellbore.
The inversion is initially validated using synthetic scenarios with various complexities. Subsequently, the algorithm is applied to field datasets, all of which resulted in 3D reservoir maps derived from deep-directional resistivity measurements. Examples include consistent imaging of faults parallel to the wellbore, and imaging when the tool is approaching, crossing, and moving away from one or multiple faults.
Michael Thiel is a Principal Research Scientist at Schlumberger-Doll Research Center in Cambridge, MA. He joined Schlumberger in 2010 after receiving his PhD in electrical engineering from the University of Michigan. He is working at Schlumberger-Doll Research in Cambridge, MA, on inverse problems and interpretation workflows for LWD directional resistivity measurements.