Holistic Approach Uses Electromagnetic Tools, LWD Data To Improve Reservoir Understanding
Authors: Carpenter Chris 
Published: January 2024

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215519, “A Holistic Approach to Data Interpretation Combines the Strengths of Ultradeep Electromagnetic Tools With Shallow Logging-While-Drilling Data To Improve Reservoir Understanding,” by Karol Riofrio, SPE, and Nigel Clegg, Halliburton, and Luke Rawsthorne, Aker BP, et al. The paper has not been peer reviewed.

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During drilling operations, logging-while-drilling (LWD) tools, which have greater resolution than seismic, are deployed to aid in decision-making and optimize well placement. Focusing on the data sources in isolation can lead to successful wells, but placing this data in a geological context allows for more-sophisticated decision-making and leads to greater reservoir understanding. Key to linking the near-wellbore measurements with the geological models derived from seismic interpretation are ultradeep electromagnetic tools. The authors describe an approach in which all available technologies are combined to improve reservoir understanding of different depositional environments.

Geological Background
Deep marine turbidite deposits are recognized as an important hydrocarbon reservoir type; many recent major hydrocarbon discoveries and field developments worldwide occur in sediments deposited by turbidite currents. Turbidite deposits are characterized by a variety of elements such as large-scale erosive features, channels and channel deposits, overbank deposits, lobes, and channel/ lobe transition zones. Each of these elements contains distinctive characteristics.
In this complex setting, better definition of the elements present in the reservoir significantly decreases uncertainty while drilling and can improve the completion design, lengthening well life. Applying different well-acquisition technologies such as ultradeep resistivity (UDAR) inversion and anisotropic inversion and interpretation methodologies such as petrophysical analysis, correlation with spectral decomposition volumes, and 4D seismic can help initially for well placement and subsequently for well-completion design and future development of analogous fields.

Methodology
The complete paper provides the background, characteristics, and advantages of the following methodologies that the authors used in the study:
- 1D UDAR inversion
- 3D electromagnetic UDAR inversion
- 3D electromagnetic UDAR inversion for anisotropy
- Spectral decomposition
- 4D Seismic

Case Study
The strength of combining these tools can be demonstrated in the approach to understanding the results of a single well. In the target well, the main goal was to drain the remaining oil identified by 4D seismic in the target structure. Among the complexities acknowledged predrilling was an undulating oil/water contact (OWC) identified as a result of production from previously drilled wells in the area, the lithological complexity of the reservoir resulting from the turbiditic depositional environment, and the filling history of the field. Identification of these complexities highlighted that the chance of exiting the hydrocarbon-bearing zone was high because of the potential for structural uncertainty and a complex, undulating OWC.