Optimizing a Unique New Generation LWD Technology for Petrophysical Evaluation, Well-Placement, Geological Mapping and Completion Design-Carbonate Reservoir Case Study

Abstract

Abstract The task of drilling and completing horizontal development wells in carbonate reservoirs can prove to be quite difficult, especially in the well placement and completion design stages. These stages of well construction can be particularly challenging when the reservoir is characterized by natural fracture systems which can result in drilling fluid losses, or when drilling with narrow TVD targets. The utilization of high resolution borehole images to optimize petrophysical evaluation, well placement, and completion design becomes a necessity for reservoir evaluation team. This paper will present a case study of how this new LWD technology optimized well placement, and completion design. During the pre-job planning stage, numerous scenarios are considered to assist in determining which "bundle" of logging technology is best suited to achieve the objectives of drilling the well. Optimizing logging design specifications required to meet the objectives may not be a simple job. For instance, placing the lateral near the roof of the reservoir while getting resistivity measurements that are least affected by overlying beds would seem to be irreconcilable. Similarly, acquiring high quality resolution image data in the event of borehole deterioration associated with total drilling fluid losses is a difficult task to achieve. In this case study, the technology is shown to successfully "geo-steer" within a single thin layer of the reservoir and achieved a 100% net-to-gross while simultaneously placing the wellbore near the roof. The real-time high resolution image was of sufficient quality used to identify sub-seismic faults, natural conductive fractures, karst dissolution features, healed fractures and drilling induced fractures as the well was being drilled. Once the well was drilled to the planned total depth, the high resolution image data could be used for the completion design, thereby saving the time, expense, and risk of an additional logging run using pipe-conveyed wireline logging tools. In addition to the completion design, high confidence dip data were used to update the geological models, fracture porosity and aperture were computed from the images and the shallow focused resistivity measurements were used for more accurate saturation calculations.