Real-Time 3D Modeling from Electrical Image Lwd - a Case Study from Offshore Abu Dhabi

Borehole image logging-while-drilling (LWD) technology was used to derive the near-bore stratigraphic and structural orientations, and the seismic section was effectively upscaled in real-time to provide accurate geosteering decisions.

The Satah Al Raz Boot (SARB) field development project aims to produce an additional 105,000 bpd for the United Arab Emirates, with the majority of the production from the Arab D formation. Developing the Arab D formation is critical to achieving this goal, however it is particularly challenging to drill.

The Arab D formation consists of laterally deposited, yet discontinuous, bodies of anhydrite, limestone and dolomite. As a consequence of the lateral discontinuity, correlation throughout the Arab reservoir section to nearby offset or pilot wells is challenging:

Creating a cross section from dipmeter tools was first outlined by Etchecopar and Bonnetain in 1992, and subsequently been used to model a variety of depositional environments (e.g. Marchon et al., 2016 ; Amer et al., 2011 ; Koepsell et al., 2011 ). Projecting the structure away from the borehole can be used to upscale the 3D model and reduce the structural uncertainty of the immediate area. To maximize the benefit of 3D modeling while geosteering, the structural modeling must be done in real-time and must be accurate enough to identify slight variations in formation dip.

In most cases, when the wellbore is near-parallel to formation dip, a non-sinusoidal feature can be observed from the borehole image. A method created for extracting the orientation data from features that are non-sinusoidal has been created ( He et al. 2016 ). The outcome is a more accurate layer zonation—resulting in a more accurate True Stratigraphic Thickness (TST) calculation. The new and accurate method to pick image features was used to create a 3D model in real-time operations, and was used to proactively geosteer Arab D wells in 3D space.