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APPLIED PETROPHYSICS (Introductory and Advanced Courses)
Content Summary of Modules Currently Available
- Course Introduction
A short lecture explain the course layout, timing and expected learnings.
- Introduction to Logging
An overview of what constitutes a log and the surface and downhole logging equipment and practices used to create a log.
- Introduction to Petrophysical Technique
A summary of the petrophysical task, work flow and how these will be approached in more depth during the rest of the course.
- Fundamental Rock and Fluid Properties
Reservoir properties, the object of formation evaluation, are discussed in this lecture along with the geological processes which control those properties. An understanding of the role of core analysis in formation evaluation is also touched on here.
- Wellbore Environment – Drilling, Caliper, Temperature (a 3-lecture suite)
These three separate lectures investigate the wellbore and hence logging environment. They describe how the drilling process disturbs the static geothermal gradient and creates a wellbore environment which is measured with the caliper.
- Qualitative (Quicklook) Interpretation
Prior to quantifying formation properties in a petrophysical analysis, the petrophysicist must be able to quickly identify reservoir/non-reservoir, hydrocarbons vs water, porosity vs tight formation and distinguish oil from gas. All this without the use of a computer is achieved from a visual inspection of the logs.
- Sedimentary Environments
Identification of marine and fluvial environments is achieved from log stacking patterns. This helps the petrophysicist identify key grain size variations and provides insight into likely mineral assemblages, key to a successful analysis.
- Log to Core Integration
The full integration of log and core data (plus pressure and mudlog data) is a requirement of a successful petrophysical analysis and discriminates petrophysics from the single component log analysis. Good and bad log and core data sets are also reviewed for Internal consistency and confidence.
- Shale Volume Determination
Shale is defined and various clay types discussed. Quantification of shale volume is explained using simple Gamma Ray and density-neutron techniques. Gas impact on the results is explained.
- Gamma Ray
The occurrence of naturally occurring radionuclides and their measurement by spectral and total gamma ray tools are described. The physics of the measurement and operation of the GR tool are also covered. Diverse applications of the GR curve are listed.
- Spontaneous Potential
Naturally occurring sources of the spontaneous potential effect are described and qualitative and quantitative uses of the SP curve are reviewed.
The sources of density differences between various lithologies and fluids, and uses of the density measurement to calculate porosity and other formation properties are reviewed. The physics of the density measurement is discussed along with the operation of the basic density tool.
Openhole and casedhole applications of the neutron tool are discussed. The tool physics and operation of the standard neutron tool are explained including matrix and environmental corrections. The impact of gas and low porosity on hydrogen index is explained as well as scaling of the neutron and density curves to be formation matrix compatible.
- Sonic Part I
Wave propagation of compressional and shear waves is explained and illustrated. Operation of a basic first arrival compressional sonic tool is described. Cycle skipping is described and various porosity transforms are introduced.
- Sonic Part II
A second advanced sonic module can be presented which describes array sonic tools, STC processing, various QC techniques and introduces elastic moduli and acoustic anisotropy.
The tool physics of the NMR measurement is described for both circumferential and azimuthal tool types. Identification of pore size distributions is explained, as is the calculation of porosity using the density-magnetic resonance method. Advantages and limitations of NMR porosity logging are explained.
- Summary of Porosity Method
Density, neutron, neutron-density, sonic, NMR and resistivity porosity methods are summarized in common formats listing strengths and weaknesses of the various methods. The usage of density-neutron log crossplots to calculate carbonate and sandstone porosity is introduced.
Density-neutron plots and crossplots are examined in detail to identify lithology and fluid types to assist analysis. Sandstones and carbonates examples are addressed.
- Verification of Fluids
Acquisition and uses of downhole pressure to identify hydrostatic fluid gradients used for formation fluid content are explained. Operation of several downhole pressure tools and packers is described. Near wellbore effects such as supercharging are explained.
- Archie’s Law and Borehole Environment
The derivation and application of Archie’s Law to calculate water saturation are explained. The formation of an invaded zone and its impact on resistivity logs and the saturation calculation is described.
- Resistivity and Conductivity Log
Electrical current flow through the formation is discussed, including the development of the formation factor F concept. This is followed by a description of the design, operation and depth of investigation of various resistivity tools.
- Archie Parameters_ Water Saturation
Various methods for deriving Rw are discussed and the role of core analysis in deriving electrical properties “m” and “n” and typical ranges are illustrated.
- Effective Porosity & Saturation
The standard model used for subdivision of total porosity into micro and macro components and the distribution of fluids in both is explained. The use of mercury injection and porous plate drainage capillary pressure to quantify pore types is illustrated.
- Permeability Estimation
Concepts of fluid flow in macroporosity networks are developed using mercury injection data to quantify macro and microporosity in samples. Herron, Timur and Timur-Coates permeability equations are explained.
- Capillary Pressure
The basic physics of interfacial tension and wettability and their role played in capillary pressure are described. The importance and methodology for calculating maximum column height when planning capillary pressure experiments is explained. Various laboratory methodologies and their strengths and weaknesses are shown. Finally, the integration of log and capillary based water saturation is illustrated. The lecture concludes with a discussion of the use of “J” functions to calculate water saturation.
- Net Pay
Net pay is defined and quantified. Techniques employing both log and core data to define both shale volume and porosity cutoffs are explained.
- Overview of Log Interpretation
This talk summarizes some of the previous density-neutron plot material and extends their use to calculate porosity in dual mineral systems such as dolomite-calcite. Various other petrophysical crossplots such as Hingle and Pickett plots are introduced.
A comprehensive talk covering the development of LWD, wireline/LWD selection criteria, BHA configuration, telemetry systems, circumferential vs azimuthal tool design, tool physics of common quad-combo tools, data quality control.