Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Earth science
Reexamination Certificate
2002-12-12
2004-02-10
McElheny, Jr., Donald E. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Earth science
C703S010000
Reexamination Certificate
active
06691037
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to the field of well logging. More specifically, the present invention relates to methods for formation permeability estimation.
2. Background Art
Reservoir characterization is important for oil and gas production. Knowledge of formation properties is essential for effective management of the production process. Among all formation properties, permeability (or fluid conductivity) is the most difficult to determine or predict. Permeability is a measure of the ease with which a formation permits a fluid to flow through it.
To be permeable, a rock must have interconnected porosity (pores, vugs, capillaries, fissures or fractures). Greater porosity usually correlates with greater permeability. However, this correlation does not always hold true. For example, a formation of fine-grained sands may have highly interconnected pores. However, these pores and pore channels are too small and the paths available are too restrictive for fluid movement. Therefore, the permeability of a fine grained sand formation may be quite low.
While formation permeability may be directly determined using core plugs in the laboratory or using a formation fluid tester in a wellbore, these measurements are only practical for providing discrete points of permeability values. Therefore, there has been an intense interest in using models to predict formation permeability profiles from other well logging data.
Many investigators have attempted to grasp the complexity of permeability function into a model with general applicability. Most of models developed are empirical models based on correlation between formation permeability, formation porosity and irreducible water saturation. See e.g., Balan, B. et al., “
State
-
Of
-
The
-
Art in Permeability Determination From Well Log Data: Part
1
—A comparative Study, Model Development
,” SPE 30978, presented at the SPE Eastern Regional Conference & Exhibition, Morgantown, W.Va., Sep. 21, 1995.
The empirical models typically involve measuring porosity and irreducible water saturation of the core and developing mathematical models relating porosity and irreducible water saturation to permeability. In order to use this approach, it is necessary to obtain effective porosity, which is the portion of the porosity that is not isolated and is connected to the pore network and therefore can contribute to fluid flow, and irreducible water saturation. These parameters are not available directly from well log. Instead, they are estimated from other well log data. However, porosity derived from well log data is not necessarily effective porosity, and methods for deriving irreducible water saturation often rely on effective porosity. Furthermore, empirical models developed for certain formation perform poorly when used in other field. See Mohaghegh, S. et al., “
State
-
Of
-
The
-
Art in Permeability Determination From Well Log Data: Part
2
—Verifiable, Accurate Permeability Predictions, the Touch-Stone of All Models
,” SPE 30979, presented at the SPE Eastern Regional Conference & Exhibition, Morgantown, W.Va., Sep. 17-21, 1995.
It is desirable to have methods for providing more accurate formation permeability profiles, which match formation log data obtained from fluid flow measurements. In addition, it is desirable that such methods are generally applicable to various formation permeability models.
SUMMARY OF INVENTION
An aspect of the invention relates to methods for calibrating a formation permeability model with respect to data obtained from fluid flow measurements. A method according to the invention includes determining a correlation coefficient for a porosity-irreducible water saturation relationship; determining a leading coefficient for a formation permeability model; and determining at least one exponent parameter for the formation permeability model by minimizing a basis function that represents a difference between a formation permeability estimate derived from the formation permeability model and a formation permeability estimate derived from the fluid flow measurements.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
REFERENCES:
patent: 6571619 (2003-06-01), Herron et al.
SPE 12113Combining Production History and Petrophysical Correlations to Obtain Representative Relative Permeability Databy Roosevelt Meads and Zaki Bassiouni, no date.
Calibrating Log-Derived Permeability by Well System Analysisby Aaron M. Cheng.
A New Approach to Improved Log-Derived Permeabilityby George R. Coates and J.L. Dumanoir.
The Producibility Answer Productby George Coates and Stan Denoo.
Permeability Estimation: The Various Sources and Their Interrelationshipsby Usman Ahmed, S.F. Crary and G.R. Coates.
SPE 56658Electrofacies Characterization and Permeability Predictions in Carbonate Reservoirs: Role of Multivariate Analysis and Nonparametric Regressionby Sang Heon Lee, Akhil Datta-Gupta, no date.
Using Log-Derived Values of Water Saturation and Porosityby R.L.Morris and W.P. Biggs, no date.
Reservoir Permeability Estimation From Time-Lapse Log Databy C.Y. Yao and S.A. Holditch.
SPE 24757The Profile Permeameter: A New, Fast, Accurate Minipermeameterby S.C. Jones, no date.
SPE 30581Invasion-Based Method for Estimating Permeability From Logsby M.E. Semmelbeck,, J.T. Dewan and S. A. Holditch, no date.
SPE 35650Application of Permlog—A New Log-Based Permeability Estimation Methodby M.E. Semmelbeck and I.R. Diyashev, no date.
SPE 71721Imparting Directional Dependence on Log-Derived Permeabilityby J.H. Schön and D.T. Georgi and O. Fanini, no date.
SPE 13346Reservoir Description Using Well Logsby Douglas W. Hilchie.
SPE 17980A Field Study and Mapping of Permeability in Gulf of Suez Sandstone Reservoirsby M.R. Khafagi, no date.
SPE 22297Permeability From Logs: A Hypermedia Microcomputer Tutorialby W.A. Nagel, no date.
Estimating Production of Prospective New Wells with Log Derived Permeability Feet(Kh Mapsby Alvin L. Schultz.
A Method for Reconciliation of Log-Derived and Core-Derived Porosityby P Cooke-Yarborough.
Average Water Saturation from Capillary Pressure Databy L. Paul Westbrook and W. John Lee, no date.
Permeability Averaged Capillary Data: A Supplement to Log Analysis in Field Studiesby A. Johnson.
Permeability Indication with Conventional Sonic Waveformsby John P. Castagna, Sandy M. Zucker and Thomas G. Shoberg.
Determination of In-Situ Permeability from Tube wave Velocity and Attenuationby D.R. Burns and C.H. Cheng.
Tube Wave Attenuation and In-Situ Permeabilityby Albert T. Hsul, Zhang Jinzhong, C.H.Cheng and M.N.Toksöz.
Log Derived Permeability and Flushed Zone Saturation Utilizing High Frequency Electromagnetic Wave Attenuation and Propagation Timeby T.D. Scott, Jr. and C.C. Purdy.
Butsch Robert J.
Poe Bobby D.
McElheny Jr. Donald E.
Nava Robin
Schlather Stephen
Schlumberger Technology Corporation
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