E. A. (Ed) Clerke, Ph.D.

Ed Clerke is a Geological Consultant in the Geological Modelling Division/Reservoir Characterization Department of Saudi Aramco.

Previously, he held the positions: Head of Petrophysics, Petrophysical Engineering Advisor for Pennzoil, Senior Principal Petrophysicist with ARCO in Plano, Texas and Petrophysical Engineering and Research Positions with Shell Oil Co. USA.

Ed received his Ph. D. in Physics from the University of Maryland in 1982 and has published articles in GeoArabia, SPE Journal, Log Analyst, SPE Production Engineering, Physical Review, Physica and the Journal of Physical Chemistry and received the Best Paper Award at GEO 2006 and GEO 2004 for work presented on Arab D Limestone Pore Systems and also received the 2006 Best Paper Award at the SPWLA Carbonate Permeability Topical Conference. Less recently, Ed received the 1993 Best Paper Award from the West Texas Geological Society for work in Permian Basin carbonates. He holds five patents, four in the area of downhole acoustic imaging technology.

Abstract 1
The Macropore and Micropore Systems of the Ghawar Arab D as Sampled by the Hagerty Cantrell Mercury Injection Capillary Pressure Data Set E. A. Clerke

The pore systems of the Ghawar Arab D as sampled by the Hagerty Cantrell (December 1990, EPR.74PS.90, Hagerty, R.M., Cantrell, D.L., Reservoir Rock Classification Arab –D Reservoir Ghawar Field, Saudi Arabia) mercury injection capillary pressure data set (125 out of the 378 samples) have been extensively examined and analyzed.

The mercury injection capillary pressure curves have been analyzed using the Thomeer type curve matching procedure. The result of this process is that the capillary pressure curve data (~200 pressure points) for each sample is reproduced with an equation defined by 3 (monomodal) or 6 (bimodal) parameters. Only four of the 125 samples required 9 parameters.

These 3, 6 and rarely 9 Thomeer parameters were entered into a large spreadsheet containing all other descriptive and measured parameters for each plug sample. The sample data (125 samples by 30 attributes) were then extensively exercised using statistical tools in Excel and SAS.

This paper will review some of the findings of this intensive statistical effort with major implications on the integration of geological parameters, petrophysical parameters and reservoir modeling.

The presence or lack of microporosity (monomodal or bimodal), is itself an indicator apparently related to facies.

• Microporosity can be mathematically classified into two distinct classes.
• Type 1 microporosity is partially effective (contributes to the sample permeability) and is associated with CLADO (100%), SRAC (100%), SO + 3sb (88%).
• Type 2 microporosity is less effective and is associated with BCGI (91%), SO-3sb (90%).
• Permeability predictions based on porosity only are very incomplete.
• Permeability predictions based on the first pore system Thomeer parameters are a vast improvement but still underestimate the total permeability for bimodal samples above 150 md.
• FZI methods applied to the simplest pore system (monomodals) do not support the unit slope requirement.

Abstract 2
The Rosetta Stone Project – I
Spectral Analysis of the Pore Geometries and Their Relationships to Depositional Facies for the Arab D Limestones E. A. Clerke, Mueller, H. W.

The Rosetta Stone project was launched to investigate the observation that one class of depositional facies descriptors also clearly subdivided the sample set by pore system properties. In 2001, Aramco acquired a much more extensive data set from 10 cored wells and containing: geological, petrophysical and reservoir property data.

This massive MICP data set was acquired on 484 samples from ten wells in a major carbonate reservoir and sample MICP data were all analyzed using the Thomeer method. Statistical reduction of the frequency occurrence of Thomeer parameters that arise from these fits to the Rosetta Stone samples show:

A new carbonate porosity concept is founded – Porositons, which are distinct and separable Pore Throat size distribution modes, and the existence of Porobodons is conjectured, which are distinct and separable Pore Body size distribution modes.

• Four porositons are the fundamental building blocks of the Arab D limestone pore systems (M: macroporosity and Type 1, 2, 3 microporosity)
• Porositon, M, carries 99.98% of the permeability of the multimodal pore systems
• Porositon 1, is a form of microporosity prevalent in the best reservoir rocks
• The Arab D limestones contain only nine pore system combinations which are made up from one or more of the four porositons, e.g., M_1
• Each of the HWM geologic facies are characterized by a small number of the porositon combinations
• A common limestone matrix pore system, M_1, acts to a first approximation as a dual porosity – single permeability system
• The presence of porositons and potentially porobodons, infers that mode analysis of NMR signals can applied for Arab D limestone facies detection
  
  

Abstract 3
The Rosetta Stone Project – II
Spectral Analysis of the Pore Geometries and Their Relationships to Reservoir Properties for the Arab D Limestones E. A. Clerke

The Rosetta Stone project was launched in 2001, to acquire a much more extensive data set from 10 cored wells and containing: geological, petrophysical and reservoir property data.

Four porositons (distinct and separable pore-throat size distribution modes) are the fundamental building blocks of the Arab-D limestone pore systems. The “M” porositon (macroporosity) carries 99.98% of the permeability of the multimodal pore systems. Of the three forms of microporosity, the one with the largest pore throats (porositon “1”) is prevalent in the best reservoir rocks (that is, they have an “M_1” porositon combination). The presence of macropores and micropores, e.g., M_1, in certain of the HWM facies types causes them to act to a first approximation as dual porosity – single permeability system.

Conclusions about the relationships between porositons and reservoir properties include:

Efforts on permeability modeling are focused on the M porositon resulting in an improved permeability model

• Relative permeability shows significant pore geometrical controls in addition to wettability, especially in that microporosity contributes to measurable relative permeability primarily through a water saturation offset
• Among a range of M_1 dual porositon samples prepared consistently with regards to wettability, Type 1 microporosity controls the water saturation value at which the oil relative permeability curve, Kro, starts to decrease from 100%.
• Among a range of M_1 dual porositon samples prepared consistently with regards to wettability, the curve shape of the oil relative permeability curve, Kro, as it declines from 100%, is controlled only by the permeability of the M porositon and steepens as that permeability increases.
• Ultimate recovery forecasts from relative permeability concepts require knowledge of the micro and macro pore systems.
  
  

Abstract 4
Permeability and Microscopic Displacement Efficiency of M_1 Bimodal Pore Systems in Arab-D Limestone Edward. A. Clerke, Ph.D.

Detailed and extensive studies of the pore systems of the Ghawar Arab D limestone have been captured in an extensive mercury injection capillary pressure data set in which all data have been analyzed using Thomeer functions. These data give new insight into the pore geometry dependence of the reservoir dynamical properties: permeability and oil relative permeability.

The dominant subgroup of the examined carbonate pore systems comprise the major Arab D reservoir section and can be described as an M_1 bimodal pore system. The M_1 bimodal pore system consists of a macropore system (M), with well defined pore throat diameters and geometries, in conjunction with Type 1 microporosity with equally well defined pore throat diameters and geometries.

The role of these macro and micro pores in the M_1 pore system has been determined for the reservoir dynamical properties: permeability and relative permeability. This work demonstrates fundamentally new pore geometry based formulations for calculating permeability and imbibition oil relative permeability and hence the pore geometry based variation in microscopic displacement efficiency for these systems. For these reservoir rocks, the appropriate pore geometrical parameters to perform ultimate recovery rock typing have been identified.

This paper presents data and formulations for improved pore system based models of M_1 permeability and imbibition oil relative permeability that reproduce measured laboratory data over a range of oil relative permeability from 1 to 0.0001 for seven waterflood composites. The relative permeability formulation uses two pore geometry variables: permeability (already shown to be a function of pore geometrical parameters) and volumes of Type 1 microporosity alone. The results show that shifts of the oil relative permeability curve to the right commonly ascribed to wettability changes also result from increasing amounts of Type 1 microporosity in the M_1 bimodal system.

Materials from Ed Clerke
Workshop Presentation
Arab D Quick Summary Presentation
Ed’s Pore Geometry of M_1 Paper
Pore System Characterization Abstract
Complexity in Jurassic Pore System Abstract
Rosetta Stone Paper
Pore Network Parameters using Thomeer Method Paper

Thomeer Swanson Spreadsheet (100pt)
Thomeer Swanson Spreadsheet (160pt)
Thomeer Swanson Frequent Questions
Spline Fitting
MICP Data Heading Record
Thomeer Swanson.xls