Evaluation of Rock Properties Determined from Core and NMR Data; A Case Study on Asmari Carbonate Reservoir

Abstract

Description of carbonate reservoir is an important in preparation of field development. An accurate determination of rock characteristics are key parameters in the carbonate reservoir description. The rock properties are traditionally obtained from different techniques, such as lab measurement, well logging, well test and so on. In this paper, data from core measurements and NMR measurements are analyzed to study petrophysical properties of Cretaceous carbonate rock from Asmari Formation. First the pore size, pore system, porosity and permeability are determined from the core measurements and NMR Analysis. Second, the results of core and NMR evaluations are compared and the reasons of differences are distinguished. In present study, initially, a comparison between the porosity values demonstrates that porosity from NMR and helium injection experiment are very similar in which He average porosity is 21.4 % and NMR porosity is 20.68%. Then, pore sizes received from the NMR model shows reliable results and acceptable match with pore size distribution determined from MICP experiment. The permeability value is modeled with NMR permeability predicting models namely Standard Kenyon and Timur-Coates. Adjusted NMR Permeability results are 17.7 (mD) and 18 (mD) for (SDR) and (TC) methods respectively and they are consistent with laboratory core permeability results (Kg=22, Kl=19.2, Kw=18.4). The pore throat distributions are also similar for two NMR and core measurement methods. This study shows how NMR analysis could be useful in determination of petrophysical parameters. Besides, the results quantitatively and qualitatively compared the reservoir characteristics of carbonate rock between core and NMR experiments.