Luis Chacin from Halliburton
Gunnar Oeltzschner, Wintershall Dea; Christian Opsahl, Wintershall Dea; Kay Rehberg, Wintershall Dea; Arthur Walmsley, Halliburton.
Ultradeep Resistivity inversions integrated to near-wellbore azimuthal LWD measurements for the successful delivery of geosteering objectives, a case from the Norwegian Continental Shelf.
A drilling campaign was successfully completed in two adjacent fields of the Norwegian Continental Shelf, with a total of five horizontal wells employing a diverse range of geosteering techniques and tools to overcome the geological and operational challenges.
On Field A, two wells (A-1 and A-2) were drilled to produce oil from a Middle Jurassic marginal marine reservoir. The structural uncertainty and extensive faulting required the use of a Logging-While-Drilling (LWD) Ultradeep Azimuthal Resistivity (UDAR) technology to land and navigate within the target sandstone units. This technology secured delivery of the reserves in the heel section and maximized sandface exposure in the toe section where seismic uncertainty was higher. As expected, several faults were encountered during the drilling of these wells, UDAR inversions providing good resolution of the IH2-Lower reservoir boundaries across the faults enabling proactive decisions to be made to meet the well delivery objectives.
Similarly, the wells B-1 and B-3 drilled in Middle Jurassic formations on Field B employed UDAR technology. In conjunction with Density image log interpretation, this mitigated the operational risks associated with the uncertainty of top reservoir depth and fluid contact. The B-1 well, designed to be placed in the uppermost sandstone unit of the target formation, was landed and steered within the pay zone with confident imaging of the top reservoir structure from the UDAR technology. On the second well drilled in this field, B-2, dip interpretation from density images was used as the primary geosteering technology due to the lack of resistivity contrast. The heterolithic facies of the reservoir made it an unsuitable candidate for the use of UDAR. Despite the challenging stratigraphy and the lack of UDAR imaging, B-2 was drilled to TD accomplishing the expected reservoir exposure in the thin target sandstone. Lastly, the B-3 encountered pressure-depleted reservoir invaded by the water from the local aquifer. Nevertheless, the well was placed in the target zone with the UDAR inversions following the lateral continuity of residual hydrocarbons and the density image providing insight on the dip of the formation.
The results presented in this paper illustrate how the imaging provided by UDAR can be integrated with shallower azimuthal sensors suitable for borehole image analysis in order to meet specific challenges. This is particularly important for cases where the use of UDAR is constrained by environmental conditions such as the absence of suitable resistivity contrasts within the target formation.
Currently working as Geosteering Technical Advisor for Halliburton Norway with 15 years of experience in Geosteering operations in various locations in South-North America and Europe. Background in Geophysics, log analysis and operations geology.