Geosteering in Complex Mature Fields Through Integration of 3D Multi-Scale LWD-Data, Geomodels, Surface and Time-Lapse Seismic
by Frank Antonsen, Equinor
was presented on Wednesday the 5 th of December, 2018.
Success of horizontal infill wells targeting bypassed zones are challenged by uncertainties in the reservoir description and by fluid content variation generated by differences in sweep efficiency over time. Optimizing well placement of such producer wells has a direct impact on cost and recovery. This could, also, potentially unlock targets not accessible today with currently used methods and technologies. Innovative interpretation methods based on efficient measurements to map structure and fluids around high angle and horizontal wells while drilling are critical for future success in a marginal, but increasingly strategical, business on the Norwegian Continental Shelf (NCS).
Novel integration and advanced 2D inversions allows lateral identification of structural and fluid events tens of meters from the borehole. Therefore, in an unprecedented manner, this paper presents new possibilities to remotely map azimuthally not only the geological structure but also the fluid distribution that was only possible before by drilling into the zones of interest.
The presented methodology has been developed with the aim of building a realistic, high resolution geomodel reconciling subsurface measurements made at different scales, including real time logging while-drilling (LWD) measurements, 1D and 2D resistivity inversions, interpreted dips and time lapse seismic data. This methodology describes how ultra-deep directional resistivity measurements and inversion-derived reservoir maps bridge the gap in scale and resolution between the standard LWD acquisition and the surface seismic data. Moreover, a novel full 2D deep azimuthal inversion of the ultra-deep directional resistivity measurements generates 2D images in plane perpendicular to the wellbore providing substantial new information to delineate the 3D reservoir structure.
This workflow determines the fluids distribution with greater certainty by combining the deep azimuthal resistivity profiles with the time-lapse surface seismic.
The methodology was applied in a horizontal infill well in an offshore Norwegian field. Integration of subsurface measurements unveils both the 3D complexity of the geological environment, including subtle faults, and the fingering water front coming sideways at the toe of the well.
The case study presented illustrates how reconciling logging while drilling measurements, ultra-deep directional resistivity inversions with surface seismic, time-lapse seismic and sedimentological and structural models is essential to enable reservoir mapping in complex geological structures with fluid flooding. The integrated interpretation from measurements made at different scale can significantly improve the understanding of the 3D reservoir structure and fluids distribution around a horizontal well. The integrated workflow has been beneficial for the planning and drilling of horizontal wells, especially to optimize geosteering for productivity of infill wells in the complex settings of mature fields.
Frank Antonsen is a specialist in reservoir geology and petrophysics at Equinor Research Centre in Trondheim, Norway. He has close to 20 years of experience from the oil industry with focus on R&D activities within petrophysics, i.e. NMR logging and core analysis. Deep look around technologies for well placement and reservoir characterization has been his main research topic since 2007.