Quantitative Petrophysical Characterization of Original Super-Permeability Zones of Bioclastic Limestone Reservoir
Super-permeability zones, as a kind of special pay zones, commonly exist in Middle East bioclastic limestone reservoirs, which enhanced the heterogeneity of the reservoirs and caused some severe issues for the development of these reservoirs. The most obvious features of the super-permeability zones in bioclastic limestone reservoirs are: low thickness, high intrinsic permeability, and the high permeability ratio between super-permeability zones and their adjacent zones. As the super-permeability zones are mainly distributed in conventional pay zones, which mean that there are lack of effective barriers or interbeds between super-permeability zones and adjacent regular zones, thus, some serious problems have evolved from water injections such as the low vertical sweep efficiency resulting from fingering of injected water in high permeability zones. However, due to the thinness and weak logging response of the super-permeability zones, it is a challenge to effectively characterize them quantitative by log data. On the basis of specific character of Mishrif reservoir in this study, first super-permeability zones were divided into two types, named type I and type II; Then we characterized macro- and micro- characteristics of super-permeability zones based on Dunham’s rock typing, conventional core analysis data including porosity and permeability, core thin section and core photos, capillary pressure curves from mercury injection, etc.; Next conventional and special log responses (including magnetic resonance (CMR) and formation micro-imager (FMI)) were analyzed and a log identification method for super-permeability zones was established from gamma ray (GR), deep induction resistivity (ILD), and porosity (PHIE), named by RTGRP-TF, which was verified by injection and producing profiles from production logging data, and saturation changes from RST and PNL data. The vertical and planar distributions of super-permeability zones have been obtained from the above log interpretation results, which provide an effective technical support for the waterflood development and dynamic production data.
KeywordsSuper permeable zones Bioclastic limestone reservoir Macro- and micro- characteristics Log identification method named RTGRP-TF Rock typing
National Natural Science Foundation of China “Research and application on key injection development techniques in bioclastic limestone reservoirs in Iraq” (2017ZX05030-001).
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