Utilization of Borehole Image Logs to Estimate Permeability in a Carbonate Reservoir
Tahereh Mirzadeh1, John Quirein1, and David Chernicky2
1Reservoir Evaluation Services, Halliburton, Houston, TX
2Geology, New Dominion LLC, Tulsa, OK
Borehole electrical images are mainly used for comprehending the structure and sedimentary features which help in better understanding of the depositional environment of a reservoir.
In recent years borehole images have been integrated with different specialty logs like magnetic resonance, dipole sonic and formation testers to help in understanding the petrophysical characteristics of reservoirs.
Previous approaches in the study area, a carbonate reservoir in Oklahoma-USA, utilized conventional logs to determine reservoir porosity and saturations. It was observed that permeability determined from a porosity-permeability (Phi_K) transform does not correlate very well to the actual production. The primary reason was the variation in rock type and the presence of secondary porosity in form of vugs, fractures, molds which when connected, contribute to a significantly higher permeability.
For this Oklahoma carbonate study, high resolution image based primary, secondary & micro porosity has been estimated by integrating borehole images with conventional logs. Then a porosity permeability transform is used to estimate permeability from this image based porosity. This transform is consistent with the Jennings Lucia model based upon carbonate rock typing.
It is evident from this study that the image based approach based upon rock typing provides significant improvements over any approach using just conventional logs without borehole image data. The results have been compared with core analysis data and a good correlation between image perm and the core permeability has been observed. This correlation can be utilized to estimate an accurate permeability using borehole image logs in other well locations where conventional core data is not available.
Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery