Abstract
With the introduction of azimuthal density while drilling tool into the stream of LWD technology in the last decade, a new frontier in understanding and evaluating lateral composition and architectural variability in most reservoirs has been made possible, by the utilisation of this tool in the drilling of high angle wells in the Niger delta. The availability of imaging technology from this tool and the resultant imaging answer product has been used for detailed structural and sedimentological analysis in characterizing reservoirs beyond the resolution of surface seismic. Determination of reservoir properties based on genetic units and identification of flow zones that could potentially contribute to production were derived to enhance the reservoir models for such reservoirs and improve reservoir management.
In most cases, the optimal placement of high angle wells using the conventional well to well correlation techniques have often proved unreliable, due to unexpected lateral discontinuity in the reservoir quality. These occurrence in many reservoirs have been associated with varying sedimentary structures, micro-faulting and unexpected changes in environment of deposition, as evident in Niger delta depobelts. Resulting production from high angle drain holes has been seen to be greatly influenced by the positioning of the well bore relative to structural and formation dip, apart from other completion related problems. Formation dip and structural features have historically been acquired from wire-line logging tools. However, electric logging in high angle wells presents operational difficulties which does not encourage the use of wireline logging.. Images acquired while drilling by the azimuthal density tool provide a method of resolving the correlation uncertainties, and allow quantification of the structural and sedimentological interpretation and the subsequent production pattern across the lateral wellbores. Two field examples where azimuthal density data were acquired and utilized are analyzed. From the data analysis an extra opportunity in terms of reserves were identified.
