Placement of a horizontal power water injector well in close proximity above an impermeable, undulating, heavy oil and tar layer poses a unique geosteering challenge. The uncertainty was to determine at what vertical depth fluid mobility stopped and heavy oil began in the high porosity reservoir. The heavy oil layer is undetectable with conventional real-time LWD measurements. Furthermore, new technology devices such as Formation Pressure While Drilling (FPWD) and NMR While Drilling can be used to detect heavy oil but only after the BHA has entered the layer. A technique of combining FPWD with LWD/MWD provides the best opportunity to identify and steer away from immobile layers, minimizing the risk of completing an injection well in intervals without injectivity.

The FPWD tool was placed behind the MWD/LWD assembly. LWD data was used to provide the information to locate ideal testing depths. This prevented taking "blind" pressure readings in low porosity/low permeability intervals during drilling operations. Conclusions from the pressure drawdown and build up profile, combined with pressure and mobility data, were used to make the decision whether to continue on the current well path or to consider a directional change.

Zones with limited injection potential were avoided after initial low mobility detection by the FPWD tools. Repeated "lost-seal" or "tight" readings from the FPWD tool in high porosity zones are excellent indicators that the bottom hole assembly has entered an impermeable layer in a highly porous reservoir. Timely communication of low-to-no mobility readings generated the opportunity to geosteer the well back into permeable reservoir to meet the well placement objectives.

This paper covers two case studies demonstrating both entry into and steering away from impermeable heavy oil layers in addition to discussions on the planning and geosteering operations.

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