This course aims to provide engineers and geoscientists with a practical working knowledge of the techniques and technologies of Well Log Interpretation. Both Wireline and LWD measurements are covered, remarking upon their differences and their advantages/disadvantages, and participants work on many examples during the course to enhance their understanding. The range of measurements discussed is comprehensive, so participants are also presented with an up-to-date `shop window` of the wireline and LWD tools and techniques now available to the industry. Efforts are made broadly to cover the technologies offered by the various different service vendors, rather than only those from a single supplier.
Course Level: Skill Instructor: Richard Piggin or Kym Dutfield-Cooke
Designed for you, if you are...
An entry-level engineer or geologist/geophysicist
An experienced engineer or geo-scientist or technical assistant working with, or needing to understand better, the principles of log interpretation and/or to update yourself on the range of log measurements and techniques now available
As it is presented in separate modules, the course is appropriate for both engineers and geologists/geophysicists, and the emphasis and level can be changed depending upon the participants’ requirements and backgrounds.
How we build your confidence
Starting with the basic physics of each measurement, the inputs required for the fundamental resistivity and porosity models are explained, leading to the formulation of the Archie relationship linking them together and to the determination of fluid saturations in simple reservoirs. More complex measurements including recent technologies are then covered, which can assist in the interpretation of more difficult lithological environments.
Great emphasis is placed on log quality control, so participants are constantly reminded of the necessity to verify data quality before starting - and whilst making - an interpretation. As well logs are acquired in difficult field conditions, quality issues are frequently encountered, so helpful and practical precautions to identify problems are discussed. Furthermore, log interpretation is still largely based on empirical relationships, the applicability of which may depend on local factors, so course participants are introduced to the verification steps necessary to achieve an optimal interpretation, and are reminded that reliance on `black box` interpretation methods can lead to serious mis-interpretations.
During the course, participants will – with the active assistance of the instructor - perform interpretations on at least three data sets using a simple Excel spreadsheet program implementing standard relationships, and will thus gain an understanding of the basic methodologies used in commercial log interpretation packages.
The benefits from attending
By the end of the course you will feel confident in your understanding of:
The fundamentals of well log acquisition, quality control and interpretation such as depth measurements, the formulation of the classical resistivity and porosity/lithology models, the logic leading to the Archie relationship and determination of fluid saturation, through the use of standard Wireline "triple-combo" logs and GR spectral measurements, or their LWD equivalents
Ancillary measurements such as Formation Tester and Imaging, as well as cased-hole topics such as cement-bond logging, perforation performance issues and fluid-level monitoring during the life of the reservoir
Complex modern measurements (e.g. NMR, Dielectric, Multipole Acoustic measurements) and eventually working up to a reasonable general understanding of the difficulties and pitfalls in log interpretation in complex formations such as fractured carbonates, shaly sands and shale-oil/gas environments. The extent to which complex measurements and methods are covered will depend upon participants’ interest and time available
Day 1: General Topics and Resistivity Measurements
Overview of basic petrophysical models & relationships used in “clean” formation interpretation
Depth measurements & quality control
Conductivity in electrolytes and derivation of Rmf at formation temperature
Use of SP for geological interpretation and to determine Rw
Resistivity measurements to determine Rt , Rxo and invasion profile - Deep-reading resistivity measurements to determine Rt - Pad-type resistivity measurements to determine Rxo - Mandrel-type resistivity measurements to determine Ri - Tornado chart corrections & implications of the “step-profile” and other invasion profile assumptions
Gamma ray measurements
Identification of potential zones of interest using SP, GR and resistivity [This section is mainly the participants working through a series of log examples to illustrate the selection of zones of possible interest]
Day 2: Porosity and Mineralogy/Lithology Measurements
What is "the porosity"? Different approaches yield different results, and why?
Measurements for determination of porosity & mineralogy/lithology - Density measurements - Neutron measurements - Acoustic measurements (Azimuthal/radial stress analysis is discussed in an optional module at end of course) - Pe measurements
Crossplot methods for porosity & lithology determination
Gamma ray spectrometry and core sampling for enhanced mineralogy determination - Spectral Gamma ray - Elemental capture spectrometry
Percussion & mechanical sidewall coring
Day 3: Linking Resistivity with Porosity/Mineralogy Measurements
Linking porosity, formation factor and water saturation
Determination of water saturations in virgin and flushed zones
Crossplots (Pickett, Hingle)
Quicklook Rwa, F-ratio methods
Quicklook logarithmic overlays
Moveable oil plot
Completion & review of 1st example set of logs (“Clean Sand” example) which the group has been working on in teams over the first 3 days. Review of GoM LWD set of logs (“Homework” example) given to participants for their study after course hours
Day 4: Miscellaneous Measurements for Petroleum Engineering and Geological Applications
Pressure measurements, fluid sampling & analysis using formation testers
Nuclear magnetic resonance measurements
Permeability determination from logs & pressure measurements
Overview of computer log interpretation methods
Other geological applications of resistivity, porosity & GR spectrum measurements
Cased-hole logging measurements - Thru-casing logging for porosity and resistivity - Monitoring fluid-level changes using pulsed-neutron & gravity methods.This section includes participants interpreting an openhole & casedhole time-lapse example from northern Europe - Cement Bond Evaluation - Corrosion prediction, detection and monitoring
Perforation, skin and productivity index enhancement
Overview of production logging measurements
Day 5: Log Quality Control, Other Modern Log Measurements, Overviews of Complex Interpretations, Interpretation of Final Example
Overview of principal log quality control issues
Complex modern measurements (eg: dielectric, multipole acoustic measurements)
Overviews offering a reasonable general understanding of the difficulties and pitfalls in log interpretation in complex environments such as fractured carbonates, shaly sands, thin-bedded formations and shale-oil/gas exploitation
Participants work in groups on 2nd example set of logs, preferably from general area of course, otherwise using a standard example from the North Sea (“Forties” example)