Improved Method to Identify Hydraulic Flow Units for Reservoir Characterization

Abstract

Identification of hydraulic flow units (HFUs) is an important part of reservoir characterization. Rock samples within a given HFU are expected to have the same mean hydraulic radius. We show that the famous reservoir quality index‐flow zone indicator (RQI/FZI) technique and its recent modifications do not use the concept of mean hydraulic radius. Each predicted HFU by these methods may contain the samples with different pore structures, and further the rocks with similar structures may be distributed in more than one HFU. This makes the reservoir characterization very complicated and sometimes an erroneous process. An improved method, referred to as FZI star method (FZI*), is presented here using the base form of the Kozeny–Carmen (K–C) equation, opposed to RQI/FZI method which relies on the generalized form of the K–C equation, by proper consideration of the mean hydraulic radius concept. The presented method is verified using a large set of capillary pressure measurements.

Effect of overburden pressure on determination of reservoir rock types using RQI/FZI, FZI* and Winland methods in carbonate rocks

“…The classical approach to reservoir rock typing, a semilog plot of permeability versus porosity (Abbaszadeh et al 1996), leads to undesirable results in heterogeneous reservoirs such as most carbonated reservoirs. It is noted that there is not any mathematical support for this traditional method of rock typing (Mirzaei-Paiaman et al 2015). Fig.…”

“…where r mh is the effective or mean hydraulic unit radius. Mirzaei-Paiaman et al (2015) introduced FZI* from Eq. (9):…”

“…These techniques can be classified into two general groups: the theoretical and the empirical methods. The theoretical methods (such as rock quality index (RQI)/flow zone indicator (FZI) (Amaefule and Altunbay 1993), shale zone indicator (SZI) (Jongkittinarukorn and Tiab 1997;Nooruddin and Hossain 2011), modified FZI (Nooruddin and Hossain 2011), FZI* (FZIstar) (Mirzaei-Paiaman et al 2015) and FZI** (FZI-double star) (Mirzaei-Paiaman and Saboorian-Jooybari 2016) and PSRTI (Mirzaei-Paiaman et al 2018)) are basically derived from the well-known Kozeny-Carman equation. Empirical methods, such as Winland (Kolodzie Jr 1980;Pittman 1992;Aguilera 2002), generate relationships between porosity, permeability and a specific size of pore throat which is taken from mercury injection capillary pressure tests.…”

Modeling pore size distribution of southern Sichuan shale gas reservoirs

“…The effects of these parameters have been investigated based on the capillary tube models and fractal geometry (e.g., Hammecker et al, 1993and 2004, Cai et al, 2010Cai and Yu, 2011). When the PSD data are not available, a method that identifies hydraulic flow units (HFUs) can be used to compare the pore structure between reservoir intervals of different lithological facies (Mirzaei-Paiaman et al, 2015). This method was based on characterization of the flow zone indicator (FZI) and developed using the base form of the KozenyeCarman equation, by which samples with similar geometrical pore attributes can be classified by a distinctive HFU.…”

A Graph-Based Approach to Specify Perforation Placement in an Oil Reservoir Hydraulic Flow Unit

“…Some of them included neural networks and graphs to find out HFUs from log data, as reported by [3], [4] and references therein. Nevertheless, none of these approaches have shown yet the relationship between a HFU and its oil recovery performance.…”