Recent developments and innovations in LWD (Logging While Drilling) technologies have proven to be indispensable for facilitating precise borehole placement as well as enhancing complex reservoir evaluation. The uses of real-time azimuthal images and directional deep resistivity (DDR) for geosteering and boundary avoidance have direct and obvious impact. Less obvious, but equally valuable, are the benefits to be gained from compact tool designs, providing measurements closer to the bit and more comprehensive petrophysical analysis using advanced real-time measurements.
Drilling Maximum Reservoir Contact (MRC) wells in prolific and diverse oil fields has developed into a significant focal point for many operators. As seen in the first two case studies, proactively "placing" the trajectory of an MRC well bore in thin layers and/or laterally discontinuous reservoirs is a challenge. Adding to the challenge, uncertainties are introduced due to localized differences from the mapped level of the oil-water contact and lateral variations associated with the depositional environment. Distance-to-boundary measurements from DDR inversions were key in detecting and avoiding the oil water contact (OWC) and confining the well-bore to the thin productive reservoir intervals.
In another example, the drilling of the longest horizontal injector well to date in an onshore field is reviewed. Complexities in the placement of this extended-reach borehole included a target that was characterized by high formation dip and no offset well control. Real-time images, advanced geo-steering methods and 3D structural modeling are shown to have been invaluable in successfully placing this extended-reach borehole.
A fourth example illustrates the use of advanced formation-evaluation-while-drilling techniques to describe the petrophysical properties of a deep carbonate reservoir. Spectroscopy and capture-sigma measurements, previously only available from post-drilling log acquisition, were employed to derive more accurate mineral volumes and fluid saturation computations. Real-time availability of this information can further improve well placement by identifying better porosity development and producible reservoir intervals in this reservoir.