Characterization of a heterogeneous carbonate reservoir by integrating electrofacies and hydraulic flow units: a case study of Kangan gas field, Zagros basin

Abstract

Reservoir characterization is one of the key stages in oil and gas exploration, appraisal, development, and optimal production. During the exploration phase, core analysis and well logging are basic information obtained after the pay zone identification. This study aims to integrate the concept of electrofacies (EFs) with hydraulic flow units (HFUs) to effectively characterize Permo–Triassic carbonate formations at the Kangan giant gas field in southwestern Iran. For this purpose, well log data collected from 10 drilled wellbores and 490 core data have been analyzed based on similar clusters and statistical features in which rock-type approaches were used in order to integrate petrophysical data with facies. In particular, we used a multi-resolution graph-based clustering (MRGC) method to determine EFs and the probability plot method, histogram analysis, and the plot of reservoir quality index versus the normalized porosity to identify HFUs. Based on the data, five electrofacies and six HFUs were identified. To establish a good connection between the electrofacies and the pay zones, we analyzed wells’ cross sections to compare lithology, production potential in each zone, rock type, and amount of shale and eventually to adapt facies to flow units and determine the best quality reservoir zone. The main difference between this work and other studies in the literature is adopting a systematic approach based on integrating the geology (via EFs analysis) and engineering examination (via HFUs) to accurately characterize the hydrocarbon-bearing formations. The results of this study help in rapid and cost-effective carbonate reservoir characterization by combining electrofacies clustering and HFU analysis based on core and log data, which are available and routine information in all oil/gas fields. This, in turn, assists in developing the field, using more appropriate production and EOR scenarios, and even locating proper perforation sites.

Employing Statistical Algorithms and Clustering Techniques to Assess Lithological Facies for Identifying Optimal Reservoir Rocks: A Case Study of the Mansouri Oilfields, SW Iran

“…The samples that are on the same line have the same pore throat properties and therefore make a hydraulic flow unit. Each line defines a unique HFU and the width from the origin of the lines at Φz = 1 shows the average value for that unit [1,3,20].…”

“…The samples that are on the same line have the same pore throat prop ties and therefore make a hydraulic flow unit. Each line defines a unique HFU and width from the origin of the lines at Φz = 1 shows the average value for that unit [1,3,2 To obtain an equivalent value of FZI for each group, when we plot RQI in terms Φz in a logarithmic graph, we must obtain a line with a constant slope of 45 degrees, wh is at Φ = 50% (that is, Φ = 1) of the value Log Φz becomes zero, as a result, Log RQI becom equal to Log FZI. Using this method, the FZI equivalent to each unit of hydraulic flow c be obtained.…”

“…The petroleum industry uses the hydraulic flow unit implication to improve permeability prediction for wells with coreless intervals [1]. A hydraulic unit (geometrical shape of the hole) is defined as the main volume of the entire reservoir rock, in which the petrophysical and geological properties affecting the fluid flow are constant and normally varied in different hydraulic units [2][3][4][5][6]. The change in the characteristics of the cavity geometry determines the existence of separate regions (flow units) with fluid flow characteristics.…”

Determining the petrophysical rock types utilizing the Fuzzy C-means Clustering technique and the concept of hydraulic flow units in the Asmari Formation, SW Iran

“…Based on the seismic and structural maps of the Mansouri field, it is an anticline with gentle and low slopes in the northwest-southeast (NW-SE) direction. The northern slopes are slightly higher than the southern slopes, respectively [79][80][81][82][83] . Furthermore, 5-6 degrees, the slope of the eastern and western slopes is about 1-5 degrees.…”

“…Furthermore, the Ilam Formation illustrates open and deep marine facies. Generally, the Sarvak and Ilam Formations demonstrate evidence of an internal calcareous platform with a carbonate ramp and an interior shelf, respectively 45,50,67,81,83,[94][95][96] . Fig.…”