Advanced Geological Composition with EarthStar® 3D Service

Overview

A trilateral well targeting the Heimdal formation, located in a sandstone reservoir on the Norwegian continental shelf, was successfully drilled to exploit the undrained oil-bearing zone. Known challenges of the reservoir included its complicated internal sedimentary structures, compartmentalization, and moved and undulated fluid surfaces. The EarthStar® ultra-deep resistivity service from Halliburton was combined with advanced three-dimensional (3D) inversion technology for the first time, in real time, along with conventional logging-while-drilling (LWD) measurements, for enhanced reservoir understanding of the geology and fluids in place.

Challenge

One-dimensional (1D) inversion of electromagnetic (EM) data only reveals changes in a reservoir above and below the well path. While this may be sufficient for layer-cake reservoirs, it does not identify changes in the thickness of units and their associated resistivity values. In this complex turbidite system reservoir, changes in the target sands were expected to occur in all directions because units can pinch out and later periods of erosion can incise the reservoir. A viable solution was required to accurately represent both the lateral and vertical changes.

Solution

The EarthStar service was selected to measure and identify formation and fluid boundaries up to 225 ft in three dimensions around the borehole. The initial introduction of ultra-deep EM tools used 1D algorithms to identify the boundaries above and below the well, simplifying the EM field to five components. With the advanced 3D inversion technology of the EarthStar service, all nine components were used for true 3D mapping of the formation and fluid boundaries. The service was able to show lateral variability in addition to the vertical changes mapped by 1D inversions.

Result