Abstract
This paper presents the methodologies adopted to model a tight carbonate reservoir located in Abu Dhabi and to better predict its performance (completed with horizontal wells) under a water-alternating-gas (WAG) process. The model is built through integrating geological, geophysical, petrophysical, geomechanical, and geostatistical information.
The large-scale reservoir framework is built by integrating horizontal wells and 3D seismic data. Horizontal well results are used to improve the velocity modeling and depth conversion. The fine scale reservoir zonation is based on lithostratigraphic correlations derived from the porosity and micro-resistivity logs. Stylolitic intervals are used as stratigraphic markers to guide the reservoir zonation. The Porosity model is derived from a high resolution stochastic seismic inversion, and the permeability model is generated using cloud transforms with P-Fields applied by reservoir rock types. High-pressure mercury injection data is used to define reservoir rock types. Lorenz plots have been applied and found to be a useful technique for capturing the heterogeneity of the reservoir and determining the main flow units. Fracture analysis is conducted using cores and image logs (FMI). A geomechanical study is performed to assess the orientation of the horizontal wells in the field. A discussion on the orientation of the horizontal wells with respect to maximum principal stress versus productivity/injectivity is also addressed in this paper. A mechanistic compositional flow model is built to perform sensitivity analyses on various WAG schemes (cycle, ratio, etc). A full field compositional model is subsequently built to evaluate the field performance under various development scenarios. The field is scheduled to come on stream by December of 2005.