Log-based rock compressibility estimation for Asmari carbonate formation

Abstract

AbstractRock compressibility has many applications in the upstream petroleum industry, for example, reservoir material balance calculations and geomechanics, as related to possible formation compaction and subsidence. When measurements on core are not available, empirical correlations may need to be considered, derived for specific fields. In the study presented, the suitability of the log-based method for evaluating rock compressibility is investigated, with the aim of deriving a suitable correlation for Asmari carbonate, Southwest Iran. A stepwise log-based method of rock compressibility determination is presented, including the construction of a geomechanical earth model, MEM. In comparing a log approach with core-derived results, it was found that the log-based method showed a rather reliable estimation of pore compressibility for carbonates studied, except for intervals with extremely large wellbore washout. Although the selected procedure is similar to that used for sandstone by other researchers, involving in some cases complex procedures, a relatively good matching result could be obtained with a relatively simple procedure. To validate the results from this study, a comparison of compressibility values is made with several industry correlations. An application of formation compressibility for estimating possible formation compaction and associated subsidence is also presented. However, a minimal effect is indicated in this case, as the carbonates studied are rather consolidated. In summary, this study presents a new correlation for rock compressibility for Southwestern Iranian carbonate oilfields (Asmari carbonate), validating the applicability of a log-based technique.