CHAPTER FIFTEEN: COMPUTER AIDED LOG ANALYSIS

Table of Contents
15.00 Introduction to This Chapter
15.01 Definition of the Problem
15.02 Types of Computer Aided Log Analysis Projects
15.03 The Computer Aided Log Analysis System
15.04 The Hardware Component
15.05 The Software Component
15.06 A Software Checklist
15.07 The Human Connection
15.08 Computer Aided Log Analysis System Costs
15.09 A Review of Commercially Available Systems
15.10 In Conclusion
15.11 Exercises For Chapter Fifteen
15.12 Bibliography For Chapter Fifteen

Continue to Chapter Sixteen

Publication History: Section 15.01 through 15.05 were originally presented at 22nd Formation Evaluation Symposium, Society of Professional Well Log Analysts, July 1980 as "Economics of Log Evaluation for Large Projects". Section 15.06 through 15.09 were part of a software design project that culminated in the Intellog package developed by D&S/ARC Joint Venture. This material formed Chapter Fifteen of The Log Analysis Handbook, Pennwell, 1986. This electronic version created Sep 2002. Minor editing was undertaken to modernize the text for the Internet era.

CHAPTER FIFTEEN: COMPUTER AIDED LOG ANALYSIS

15.00 Introduction to This Chapter
This Chapter reviews the subject of computer aided log analysis from the point of view of the manager and the implementer as well as the analyst and end-user. Since the ultimate goal of this book is to make the use of computers more accessible, attractive, and affordable for log analysis, it is as important to show how and what to use as it is to document the mathematics and numerical constraints of the data analysis process.

The first few sections of this Chapter are taken from a technical paper by the author, "The Economics of Log Evaluation for Large Projects", published in 1980 by SPWLA. The balance of the Chapter comes from work done by the author to describe the next generation of log analysis systems, with the view to making them more versatile and flexible, and much more intelligent and friendly for technicians and professionals who are not programmers.

15.01 Definition of the Problem
Increases in petroleum demand, well-head price and net back to the producer have resulted in dramatic increases in gasoline prices, line-ups at the pumps, and major social changes. Likewise, it has revolutionized the role of the professional log analyst and petrophysicist in the oil industry. Market forces have pushed the log analyst, sometimes unwillingly, into the forefront of the "reserves" game.

The dilemmas posed by this situation are:

1. New applicants for such positions are relatively inexperienced, or replace people who are more experienced.

2. The urgent need for answers reduces the time the analyst has to spend on each project, thus reducing analysis quality, thoroughness, and consistency.

3. Most companies don't have an organizational infrastructure to support log analysis
activity.

The usual solution is to provide the analyst access to a computer with log analysis software, or to a logging service company or computer service bureau who have log analysis programs. The rationale is that the professional can get more done, more consistently, than by chartbook or hand-calculator methods.

Unfortunately, the expected improvement in performance or results is seldom met, as many have found from first hand experience. To evaluate the success of a computer augmented log evaluation system, we must ask the following questions:

1. Does the system (analyst plus computer plus program) get more, better, and faster answers than some other method?

2. Even if it does all the above, is the system support cost reasonable (computer, systems analysts, programmers, computer operators, technical assistants, data preparation)?

3. Is the organizational cost low enough (supervisor, clerical, filing, data gathering, computer access)?

4. Do you get answers when you need them (current wells now, reserves reports or large projects by fixed deadline)?

5. Is the professional analyst in a reasonably attractive work environment and career path (if not, he'll leave or do poor work)?

The five criteria mentioned above are especially pertinent to large projects; that is, log evaluation of many zones related by area or formation. This is true because large projects usually serve, or contribute to some important corporate goals, or are part of some submission to a regulatory agency. If log analysis results are inadequate, or cannot be developed in time to meet decision making or filing deadlines, then severe competitive or financial penalties may be incurred.

15.02 Types of Computer Aided Log Analysis Projects
There are a number of general areas in which log analysis projects may occur. These may be categorized by reference to the "Resource Triangle" shown in Figure 15.01, in which the known, proved reserves are contained within a small area at the top of the triangle. This classification of resource is usually the domain of the production, exploitation, or utilization department of the oil or gas company.

FIGURE 15.01: Log analysis and the Resource Triangle

Development of this resource generates most of the positive cash flow for the company, from which exploration activity can be funded. As a result, this is the resource which needs the best documentation, such as reserves and productivity estimates, and is required by banks, regulatory agencies, and corporate management.

Well log analysis for this purpose could encompass a review of every completed zone in which the company has an interest. This must be properly organized from inception of production, since an enormous log analysis project may result when management or government decides to request this data. These projects are often called pool studies, unitization studies, or reserves studies. Because several geoscience disciplines are usually need to complete these studies, they are often called integrated projects. More information on organizing and managing integrated projects can be found in Chapter Two.

An alternative and faster method of determining proved reserves is decline curve analysis. However, this approach is unsatisfactory with increases in petroleum demand and prices. It reflects historical production trends or techniques, and does not address the problem of recovering additional oil or gas from the existing resource base. Log analysis does not necessarily tell you how to recover more, but at least tells you where more might be recovered.

A second class of log analysis project involves exploration oriented decisions. Such projects usually include data from all or most wells in a specific block or tract of acreage. The object is to identify the second tier of the resource triangle - the unproven but promising leads found during previous drilling operations. These projects are often termed exploration or play development projects. Large amounts of oil, and especially gas, were by-passed when prices were low. Therefore, there is a relatively large reserve in the "probable" category, waiting for the exploration department, and the log analyst, to define.

Further drilling and testing (if the original well cannot be re-entered) or re-completion (if the well was cased and can be entered) are required to move these reserves from the "probable but un-proved" to the "proven" portion of the resource triangle. This resource must be evaluated for corporations to make meaningful decisions concerning lease selection, step-out drilling, and allocation of corporate resources between development and exploration. This information is also vital to any kind of economic decision regarding farm-in or farm-out arrangements.

If data and result bases are lacking, decisions are made with minimal information, resulting in a poor overall success ratio on lease acquisition and drilling.

The third class of log analysis project involves more work defining reservoir quality and prospects, rather than proving up previous hydrocarbon shows. The log analyst's tasks are similar, but he may spend more time defining water bearing reservoirs, to provide the geophysicist and geologist with data on potential reservoir conditions. We call these projects reconnaissance or review projects. They are extensions or part of exploration or development projects.

Input from the geophysical and geological departments, and the log analyst, will ultimately define drilling locations for true wildcat wells, as opposed to step-out or offset wells to proved or probable production. These wells will finally define the limits to the bottom, potential, portion of the resource triangle.

Many tight gas sands in North America have started shifting from potential to probable reserves, and in a few cases have actually moved into the proved category. The economics of large well stimulation treatments will be the most significant factor in moving more of this resource across the boundary into the proven category, since few now doubt that the resource is at least in the ground.

The fourth class of the log analysis project is the day to day evaluation of current drilling wells in which the company has an interest. If done consistently, this work significantly reduces the effort needed to evaluate data in the three categories previously described.

15.03 The Computer Aided Log Analysis System
In order to evaluate logs for the projects described above, a systematic approach using computers, is required.

A "system" for log analysis consists of hardware and software plus people (users and doers), not just computer hardware. Figure 15.02 illustrates the interaction between the components and justifies the term "system" - a word usually misused when describing computer software or hardware alone.

FIGURE 15.02: The computer-aided log analysis system

The interconnecting links in the system are its most important feature. Good communication must exist, along with mutual trust and understanding, between the "user" (the engineer, geologist or geophysicist) and the "doer" (the log analyst or petrophysicist). The analyst in turn, must effectively communicate with the computer hardware-software package and staff.

A good system must be built around a team concept, consisting of the lead or senior log analyst, a junior or trainee analyst, up to two technicians, and possibly a clerk.

The senior analyst is responsible for project definition, parameter and method selection, difficult editing, work scheduling and organization, review of intermediate and final results, presentation and discussion of final results with the end-user, and training and work allocation of subordinates. He must have a thorough knowledge of log analysis methods, and be aware of all the available features on the hardware/ software package. He can run the package effectively after a few days exposure to it and can modify programs to suit special cases.

The more junior members of the team run the package under the direction of the analyst. and perform the many clerical tasks involved in organizing and filing large volumes of data. These people must be keen and adept in the use of computers.

Log analysis should be performed on a definable zone - not on an entire well at once. As many zones as needed are run to cover all potential pay sections.

The entire well may be analyzed, but as a series of discrete zones. A run control sheet is used to describe the zones to analyze, the data available, the computation method, and parameters required, as well as a brief well history to aid the analyst. The well history is also annotated on the final results to aid discussion and understanding of the log analysis by others.

On large projects, a group of 5 to 10 related zones, preferably cored and tested, will be picked, digitized, and computed as a "batch". These are reviewed, parameters adjusted as needed, recomputed, reviewed again and eventually finalized. In the earlier stages of a large project, the batches consist of those zones with the most core and DST data available. These zones are used to calibrate log analysis parameters before un-cored zones are analyzed. The organization of this procedure and the data bases required are illustrated in the block diagram of Figure 15.03.

FIGURE 15.03: Data flowchart for computer-aided log analysis system

These stages may seem simple, even trivial or obvious, but clear definitions benefit the end-user and the analytical team. Large projects or continuous, on-going projects slow down if the job stream or data structure is unorganized or chaotic.

The two feedback loops shown in Figure 15.03 indicate that successive re-runs to optimize methods or parameters are easy, rapid, and probably necessary.

This is the key to satisfying both the technician and the professional analyst, because individual zones are usually finished completely in just a few elapsed hours instead of days or weeks. A reasonable number of zones (5-20) may be interleaved, so that different functions are performed on different zones. This is a natural outcome of the variable number of times the zone has to be re-computed.

In smaller organizations, the analysis team may be one person, and in some instances, the team and the end-user may be the same person. This does not change the need to organize and review data and results.

Other organizations use a dispersed or distributed systems approach, in which the end-user, or their technical staff, do their own log analysis. This may be successful if training and standards are excellent, and specialists are available for certain jobs.

15.04 The Hardware Component
Computer hardware is an essential, but should not be a controlling, influence in the computer-aided log analysis system. There are a number of operating modes, namely:

1. batch computer - now obsolete
2. time share terminal - eg. an intelligent terminal to a UNIX mainframe
3. stand alone desk top computer - eg. an IBM-PC with its own peripherals
4. local area network - eg. an IBM-PC connected to shared peripherals and data server
5. Internet application - eg. Internet application service provider (ASP)

These modes define the hardware type, not the brand name, that the log analysis team sees in their environment.

There are alternative sources of the computing service, namely:

1. in-house
2. service bureau
3. logging service company
4. consulting services

The hardware/software training/support package for in-house systems are available from:

1. in-house
2. leased or rented from third party
3. purchased from a third party

These categories further refine which hardware components are required at the analyst's site. For example, you may require only a terminal and printer to use a service bureau package, or no hardware to use a consulting service. However, the consulting service's hardware will influence turn around time, price, or visual quality of your results.

The mode of operation and types of hardware will affect your ability to control the numerical quality of your results, since you may or may not have control over the methods (models) or parameters used in the analysis.

The batch computer method of analysis suggests that the analyst submits one or more analysis projects to an in-house or service bureau computer. Results are available within hours or days, and will need editing, revising, and re-running unless every parameter and control function was perfect. Such systems still exist, but are disappearing as more appropriate tools become available. Batch systems are usually card image oriented, even if they have been modernized to use CRT and keyboard. A typical card layout to start an obsolete log analysis program is shown in Figure 15.04.

FIGURE 15.04: Punch card layout for an ancient log analysis system (some old programs converted to modern computers still use fixed field data formats)

Time-share terminals operate in batch or interactive modes, depending on the software package used. Batch mode merely moves the point of run submission from the computer room to the analyst's office. Interactive mode allow for quick changes to be made to the run stream based on current results or run-time failures. This ability depends on how easily changes can be made by the user and how busy the system is. This dictates how fast the change can be seen by the user. Some typical time-share work stations, as used by Schlumberger, are shown in Figure 15.05 and 15.06.

FIGURE 15.05: Schlumberger Maxi-Station of the mid 1980's

FIGURE 15.06: Schlumberger Mini-Station of the mid 1980's

The word "interactive" has come into common use, with respect to interactive graphics. True interactive graphics allow the user to modify the data presented on the graphics screen (CRT), by altering scales, data values, or annotation by commands from the keyboard or function keys. Today, it refers to the ability to move a cursor or mouse to define, select, or alter points on the screen. Some descriptive literature uses the term interactive to describe graphics that can be displayed on the screen, under user control, but without the ability to change the picture once it appears, unless the program is run over again. The term is often miss-used to indicate any terminal or desktop computer with a keyboard, with which a user could interact with the program.

Stand alone desktop systems are now inexpensive and powerful enough to perform most or all of the analysis and data handling in the analyst's work area. This reduces time conflicts with other computer system users, puts more control in the hands of the analyst and usually reduces cost and turn around time. Computer department management may perceive this approach as dissolving their department's function. This can be minimized by involving the systems group in all phases of planning and installation. Most stand alone systems can communicate via telephone lines to large computers, thus relieving the systems group's concern over isolated, unconnected hardware. Such a system is shown in Figure 15.07.

FIGURE 15.07: LOG/MATE - the first desktop computer-aided log analysis system developed by the author in 1976

FIGURE 15.08: The first desktop log analysis system, circa 1976

The best compromise for larger corporations is the distributed system, or local area network. The benefits of stand alone computer power, with personalized or unique software at each station, can be augmented by common data base management at a central site. This mode is state of the art, and some limitations on mixing brand names still exist. It is sometimes called a shared resource system and is illustrated in Figure 15.09.

FIGURE 15.09: Shared resource or local area network system

The usual hardware components required for adequate log analysis are:

1. a desktop or mini computer or intelligent terminal to a computer
2. a disk drive for local data storage (optional for terminal systems)
3. a digitizer for data entry and edit
4. a hard copy plotter for display
5. a hard copy printer for data presentation
6. a cathode ray tube (CRT) or monitor to view preliminary results, option menus, and run stream progress
7. a keyboard to enter parameters and run control instructions
8. a tape drive (optional) to read raw data tapes
9. a telecommunications connection (optional) to the outside world for data transfer to other computers
10. a graphics screen to preview results and crossplots (may be same screen as item 6 above)

Depending on the mode of operation, a number of these components may not be located at the analyst's work site. For example many organizations share printers and plotters over a LAN. Since the price of these devices is very low compared to professional salaries, one often wonders why management doesn't just put a printer at each station.

A note on brand names: buy the best you can afford from a company who will be in business five years from now. This limits the choices to three or five obvious companies. The maintenance, upgrading, and software support problems on the other suppliers is not worth the lower price. Most brands can be combined providing a telephone line or standard network link is used between components. Brand names cannot always be mixed easily at the work station without extra software or special interfaces. Standardization is coming slowly and many components can now be interconnected with little trouble.

Do not be mislead by bits, bytes, cycle-times, memory sizes, and other "factual" data. Find out if the hardware will run the desired software. The costs of converting software exceeds any price differential in hardware.

Expandability is important, but too much hardware too soon, can be financially
inefficient and cumbersome.

Although your present system may require upgrading, do not overlook the option of using an alternate supplier. Neither price, service, quality, nor performance are guaranteed by a brand name, especially if the software comes from a third party.

15.05 The Software Component
Your choice of software dictates the choice of hardware. Unless you write the entire computer program, it is virtually impossible to find a software package that complements your preconceived or existing hardware.

Some computers do have more user-friendly features than others, such as user or program defined function keys, touch sensitivity screens, or light pens.

These features are desirable in a software package, but are of minimal importance in the overall operation of the system. Operating systems and programming languages should be selected for suitability, and updating capabilities, not for preconceived benefits or faults which may be only the purchaser's personal feelings.

The software package can be broken down into a number of component parts, namely:

1. data management
2. data entry
3. data edit
4. data plotting versus depth
5. data printing versus depth
6. cross plotting
7. data summary (print and plot)
8. report generation
9. log analysis models
10. synthetic seismic models
11. spatial data plotting (mapping)
12. data communications
13. "user-friendly" features

Approximately 10 percent of the entire software package is used by the log analysis program. The remaining 90 percent is used for data management, input and output, plotting, and printing. These functions are as complicated as the log analysis function and attention here will improve user-friendliness.

15.06 A Software Checklist
The following is an annotated checklist of software features, some hardware dependent, which should be assessed when deciding to buy, lease, rent, or design a computer aided log analysis system. Many of these factors are out of your control when using a service bureau, service company, or consulting service.

1. Data Management
a. Can data be processed zone at a time
- well at a time
- batch of wells or zones at a time
- interactively (one question or menu at a time)
- by defining run stream (menu pre-selection)?

b. Can you define
- run stream
- computational intervals and their associated parameters?

c. Can the run stream and/or job control information be
- saved
- modified
- corrected
- re-used?

d. Is the file structure
- relational
- hierarchal
- both
- fixed arrays
- fixed record description
- flexible record description
- modifiable by user
- modifiable by programmer
- expandable as data grows
- expandable as new functions or parameters are required
- capable of handling all the data types and entities required?
(See Figures 15.10 and 15.11)

FIGURE 15.10: Data types for computer-aided log analysis system

FIGURE 15.11: Data base for compute-aided log analysis system

e. Is the data compacted
- to scaled integers
- to eliminate nulls or zeros
- to eliminate unneeded or unused records?

f. Can the data be catalogued
- by pool
- by zone
- by batch
- by project
- by client or end user?

g. Is the trace (depth dependent) data
- fixed length
- variable length
- infinite length?

h. Can trace data be stored
- randomly
- fixed array
- in multiple versions (multiple raw data traces or edited versions)?

i. Are trace names
- fixed by the program
- assigned by the user
- not named but numbered
- fixed but changeable by user
- fixed but changeable by programmer?

j. Are files, (projects, batches, single wells) created (opened)
- automatically by system
- by user
- by programmer start up?

k. Are files (projects, batches, single wells) easily
- copied
- backed up
- defined
- edited
- defined
- purged (deleted)?

l. Is trace data stored in
- linear vectors
- block arrays
- multiplexed arrays?

m. Can data be
- backed up by client/end user or project
- purged after backup by client/end user or project
- restored by client/end user or project

n. Can the catalogue provide
- all well names in a project
- all well names on the disc
- all curves in a well
- all other records on a well
- all system files

2. Data Entry
a. What brand names of digitizers can the system handle?

b. What brands of tape drive can the system handle?

c. Are digitizer modes switched
- by the user
- by the software?

d. What magnetic tape formats can be read, any restrictions (depth increment, age)?

e. What type of formats can the system write out, any restrictions?

f. What steps are needed to set up a digitized interval:
- corners (2, 3, or 4)
- depths (keyboard entry, cursor entry)
- skew?

g. Can the log be spaced up by redefining origin?

h. How much data is saved in memory before going to the disc? (in other words, how much can you lose if something goes wrong)

i. How fast can the cursor be moved?

j. Is data range limit checked on the fly, or after digitizing, or not at all?

k. Can you exit digitizer mode easily, correct mistakes easily, back up, rest or answer the phone without starting over?

l. Is data taken only at fixed intervals, or fixed times and interpolated?

m. Can the system digitize non-log data (e.g. maps, seismic data, core data, mud log data)?

n. Can the system read core or log data from PC-DOS floppy discs, from ASCII or other interchange format files?

3. Data Edit
a. What edit modes are available
- single point
- depth shift
- depth stretch and squeeze
- linear re-scale
- non-linear re-scale
- custom function by pre-defined or user defined functions
- add to top or bottom
- patch two or more zones together
- true vertical depth
- true vertical thickness
- true stratigraphic thickness
- copy to new file
- environmental corrections (which logs and which corrections)
- smooth/filter/average
- baseline shift or deskew (e.g. for SP)
- scale conversions (e.g. old CNL to new CNL or sandstone to limestone)
- create discriminator trace?

b. Can edits be done from
- keyboard
- digitizer
- interactive CRT?

c. Can the same edit be applied to more than one trace without further data entry (e.g. depth shifts)?

d. Can the edit sequence be saved
- re-used
- reversed?

e. Is depth shifting or rescaling interactive on the CRT?

f. Are original or edited traces saved
- automatically
- by user request?

g. Can shifted data be re-shifted or un-shifted?

h. Are these functions easy to use, with minimum potential for error?

i. Can curves be shifted (but not rescaled), to create visual overlays, by interactive CRT?

j. Can edits be done over selected intervals of each curve?

4. Data Plotting
a. Are depth scales
- fixed by program
- variable (any limits)
- defined by ratio
- defined in inches per unit depth
- labeled with both subsea and KB depths?

b. Is track layout
- fixed by program
- variable number of tracks
- variable track widths?

c. Can traces
- be put in any track
- in any colour
- with any line, code
- with any shading code
- with automatic wrap around for offscale effect
- with either smooth or square curve shape?

d. Are standard log presentations
- automatic
- defined by user
- both
- saved
- re-used?

e. Are log headers
- fixed format
- variable
- optional
- easily read as to line, code and curve name
- shaded to match plot shading?

f. Can curves be shaded
- to a user defined constant
- to a left or right border
- to another user defined curve
- to indicate clay types (what codes)
- automatically for certain curves
- to indicate lithology (what codes)
- to indicate fluid types (e.g. moved and residual hydrocarbon, bound and free water)?

g. Is background grid
- available as an option
- linear and/or logarithmic
- English or Metric?

h. Can the plot be annotated
- automatically from data base, with DST, core, perfs, formation name and user
supplied test at the correct depth
- from the keyboard
- with DST, core, production, formation names, notes, comments
- with variable character size and/or style and/or angles
- with user defined line segments to allow delimiting key elements of the plot?

FIGURE 15.12: Computer-aided log analysis depth plot - note annotation and core data on plot (many modern systems still do not offer these features)

i. Is plot length limited
- by plotter size
- by file size
- by user request?

j. What plotter brand names and models are available with this software?

k. Are they pen type, printer type, or electrostatic plotters?

l. What colours are available? Are wide and narrow widths available?

m. Can the plot be previewed on the CRT, in colour or black and white?

n. Can the CRT plot be dumped to the printer (in black and white or colour)?

o. Can the CRT image be scrolled up and down to view more than one log?

p. Is the printer the main output? If so, is it dot matrix quality or a character plot? Does it have a colour option?

q. Can the plot presentation description be
- saved
- modified
- re-used?

r. Are CRT and printer plots at convenient, conventional scales? Are the characters
easily read?

s. Will the plotter handle transparencies, odd scales or sizes for report generation?

t. Can the system handle English and/or Metric log scales
- in depth
- in log value
- convert from one to the other at plot time?

u. Can core data be plotted on top of log data, mud log data or pressure data?

v. Can the vertical scale be any of
- depth
- seismic two way time
- frequency
- pressure?

w. Can plots be spooled to a high speed plotter, either local or remote to the work station?

5. Data Printing
a. Are printouts consistent in style, with
- title, client and/or user name
- well name
- zone name
- project name
- date/signature
- page numbers
- neat columns
- meaningful column headings
- units of measurement on column headings?

b. Can the user define which columns to print (as in plot program)?

c. Can the user define print increment
- as a multiple of data increment
- as an arbitrary increment?

d. Are summary pages
- easy to read
- meaningful
- fast to generate
- capable of multiple cutoffs
- automatically generated?

e. Is printed data precision
- fixed by program defaults
- variable by user
- appropriate to the data type?

f. Can the system print
- English output from Metric data
- vice-versa
- both on the same page?

g. Are cutoffs applied at print time or with prior program module?

h. Can any other discriminators be applied or are they fixed by program?

i. What brand names and models of printers are supported?

j. How many print columns are absolutely required? How many are desirable?

k. Are print pages report size (8 1/2 X 11 inches) or larger? Do they need to be photocopied for permanence (e.g. thermal paper) or reduced in size?

l. Do the characters appear well formed with true decenders and ascenders?

m. Is net pay interval automatically flagged and summarized? Can non-pay be dropped from listing automatically?

n. Can you custom-function columns (e.g. like EXCEL or LOTUS 1-2-3) to obtain new results?

o. Can printer output be spooled to a high speed printer, either local or remote from the workstation?

p. Can both subsea and KB depths be printed?

FIGURE 15.13: Neat, legible output from computer-aided log analysis system

6. Crossplotting
a. Will the system provide
- histograms
- x-y plots
- z plots (3-D plots)
- 4-D plots (using colours)
- maps and contours
- 3-D spatial images
- with or without hidden line removal?

b. Can you plot
- any curve versus any curve
- fixed crossplots only
- standard crossplots automatically
- directional data (computed or input data)?

c. Are appropriate scales
- picked automatically
- suggested by defaults
- chosen by user?

d. Are axes labeled neatly and correctly with curve abbreviations, full names, and units?

e. Are appropriate background grids, lithology lines, and pure mineral points, or other notation provided automatically? Can this data be added to the system by the user?

f. Can you annotate comments or line segments on the plot?

g. Can you interactively select interpretation parameters on the CRT? And annotate these picks on the plot when chosen? Does plot have a current value shown for easy parameter normally picked from such plots?

h. Can you move a cursor about the plot by knob, keyboard, joystick, mouse, digitizer?

i. Can you get
- scatter plots
- grouped plots
- cumulative plots
- frequency plots
- thickness plots
- percentage plots
- composite plots (more than one zone summed)?

j. What statistics are available
- linear regression an X and Y, and reduced major axis
- minimum, mean, maximum
- non-linear regression
- multiple regression
- other statistical measures
- can user interactively provide shape and intercept for visual lines

k. Are CRT and printer plots drawn or printer character plots?

l. Can plots be previewed on the CRT and dumped on the printer? In colour? Can more than one well be plotted on the CRT and shifted to find normalization parameter?

m. Can plots be shrunk or expanded to fit reports? Can they be put on transparencies for display?

n. Can you plot core data versus log data, mud log data, pressure data, etc?

o. Can plot request be
- saved
- modified or corrected
- re-used?

p. Are commonly used plots easy to set up or automatic?

q. Can groups of different plots be batched to speed up work? Can the batch description be saved, modified, corrected or revised?

r. Can data be dropped from the discriminated plot to remove unwanted noise, bad hole effects, or background in any or all axes?

s. Can all axis be functioned at plot time?

7. Data Summary
a. Is data reduced to be useful with
- summary reserve pages
- hydrocarbon and pore volume maps
- project or pool reserve files and print out?

b. Can summaries be merged, summed, compared, edited, commented?

c. Is data converted to engineering or geological terms when necessary?

d. Can cash flow or exploration economics be calculated?

e. Can English and Metric data be merged, mixed or presented in both systems of units.

8. Report Generation
a. Does the data file structure allow interfacing to word processing?

b. Is report generation solely controlled by the user, or are conclusions drawn from the data and converted to English sentences?

c. Do canned report phrases sound reasonable? Can they be modified for each user need?

d. Does the final report integrate tabular printed data, graphics and text into a
finished product?

e. Can reports be saved, updated, revised, reprinted automatically or under user
control?

f. Can reports be edited or merged easily?

g. Are the usual word processor features available, eg. cut and paste, copy, delete, bold face, italics, underline?

h. Can the report generator access the data base by a query language?

i. Can it in-bed data base entries in the text?

9. Log Analysis Models
a. Can shale volume be calculated from
- gamma ray
- spontaneous potential
- density neutron
- density sonic
- neutron only
- sonic only
- gamma ray spectrolog
- minimum of any selected methods
- with linear or non-linear corrections
- user supplied algorithms?

b. Can porosity be calculated from
- sonic
- density
- neutron
- sonic density crossplot
- density neutron crossplot
- sonic neutron crossplot
- with shaly sand or complex lithology options
- with iterative gas and shale corrections
- with heavy mineral detection
- shallow resistivity
- microlog
- others
- user supplied algorithms?

c. Can lithology be determined by
- matrix density
- matrix travel time
- NGT/LDT combinations
- M-N calculation
- A-K calculation
- simultaneous equation solution
- error minimization (Global-style)
- principal components (Geocolumn)
- user supplied algorithms
- other?

d. Can saturation be found from
- Archie method
- Simandoux method
- Waxman Smits (CEC) method
- bulk volume water method
- dual water method
- error minimization (Global-style)
- EPT or NML data
- others
- user supplied algorithm?

e. Are minimum, maximum and material balance constraints used effectively on porosity, shale content and water saturation?

f. Is bad hole logic easy to use and set correctly? Can other discriminators be created and used to modify results or logic flow?

g. Can all parameters in the formulae be modified by the user?

h. Are reasonable defaults available for all parameters?

i. Are method choices suggested by the program automatically (by the nature of the data available)?

j. Can the methods and parameters selected be saved, modified, re-used?

k. Can user supplied algorithms be incorporated and saved as part of the system? With or without programming assistance? What parameter naming convention is used to permit this?

l. Can the models handle strange situations, such as radioactive minerals, bitumen, coal, or heavy minerals? Can the models utilize all the logs available (e.g. electromagnetic propagation, lithodensity and natural gamma ray)?

m. Are all the routines logically connected for ease of use and understanding?

n. Are all models corrected for shale, lithologic effects?

o. Are quicklook methods easy and fast; are full blown methods reliable and achievable?

p. Are productivity indicators included; eg. permeability, productivity index, deliverability, cash flow?

q. Can core data be integrated into the analysis results, and used to calibrate parameters?

r. Is the documentation of the models adequate? Are there worked examples or test data? Is the documentation current with the actual program?

10. Synthetic Seismogram
a. Does this feature use existing log data or does it require a data set different than the log analysis?

b. What method is used to create the synthetic from the depth data?

c. Is density data used? Is it corrected or edited for washed out hole?

d. What output sample rates are available?

e. What wavelets are available
- Ricker
- zero phase
- minimum phase
- user defined?

f. Can you plot and print the Fourier Transform results of the raw data, the wavelet and the convolved trace?

g. Can you further filter the data with band limiting filters?

h. Can you input real seismic traces? Real seismic wavelets?

i. Can you filter sonic and density data to correspond to frequency content inverted seismic data?

j. Can you invert a seismic trace to obtain a sonic log? How do you input the trace?

k. Can you edit logs to create hypothetical models?

l. Can you describe the rock type, shale content, porosity and fluid content to calculate what the logs should read for various hypothetical models?

m. Is the terminology on the menus suitable for use by geophysicists?

11. Spatial Data Plotting (Mapping)
a. Can data be generated from
- reserves files
- log data summaries
- user input?

b. Can data be entered on a
- digitizer
- keyboard?

c. What method is used to interpolate contours
- gridding
- triangulation?

d. Does the system draw straight lines or smooth contours? What method is used to
smooth contours?

e. Can geographic and township/range grids be generated? Will they work in all quadrants of the globe?

f. Can well name, symbol and data value be posted on the maps (optionally)?

g. Can other line segments be digitized and plotted, such as roads, geological or
geographical boundaries, geophysical lines?

h. Are the contours properly annotated? Free of angularity?

i. Can the title block be positioned to avoid interference?

j. Can the maps be plotted on various projections (Lambert, Mercator, UTM)?

k. Are there limits to the scale of the map or its size, of the plotter on which it can be drawn?

l. Can areas and volumes be determined automatically? Will it run as a planimeter for any data?

m. Can contours be edited and the areas and volumes re-calculated?

n. Can maps be previewed on the CRT and dumped on the printer?

o. Is colour used effectively?

12. Data Communications
a. What other computers will the work station communicate with? Which operating systems? Can data be received directly from the rig at logging time?

b. Does it communicate over
- telephone lines
- IEEE 488 (HP-IB or GP.IB)
- IEEE (Ether net?)
- Internet
- others?

c. What transmission rates are permitted?

d. Is the communication mechanism
- hardware controlled
- software controlled
- both?

e. What hardware is needed
- modems (R2-232)
- multiplexors
- cable/conduit
- co-axial cables
- DTE/DCE cables?

f. Can the communication mechanism be configured for
- parity (on, off, odd, even, don't care)
- number of stop bits
- word length
- end of transmission characters?

g. Does the system keep an audit trail of events
- on the local disc drive
- on the remote disc drive
- on the printer
- on the CRT?

h. Does the system translate remote log or core data files into local files useable by the log analysis system?

i. Can you access other types of data such as
- core data
- formation tops
- DST and perf test data
- production data?

j. Can this data be put into the log analysis data files and be used by the processing
programs?

k. Is the system hard wired or dial-up?

l. What data files in your area can you dial up or access directly?

m. What software is needed on the host computer to create or pre-process files before data transmission occurs?

n. What job control language knowledge is needed to log-on and utilize the host?

o. Can the log-on and job request be coded as a standard part of the communications package?

p. Can the log-on and job request be saved, modified, or re-used?

q. Is there a better way to move the data (e.g. local tape drive)?

r. What security features are available? Needed?

13. Overall Friendliness
a. Is the documentation
- complete
- easy to read
- indexed
- well illustrated
- full of examples
- bound or looseleaf
- current with the actual system?

FIGURE 15.16: Legible, understandable documentation and training manuals are essential for computer-aided log analysis system

b. Are help files
- built into the system
- easy to access (on-line)
- readable and informative
- current with the actual system
- current with documentation?

c. Is error recovery
- easy
- fail safe
- self documenting?

d. Is typing made easy by
- accepting upper and lower cases where possible
- minimizing the number of characters required
- use of labeled function keys
- uniformity throughout modules
- allowing use of defaults with no keystrokes (other than the carriage return)?

e. Is the response time for each entry or request virtually instantaneous, or is there a
noticeable lag after each entry? Is the lag a function of loading of the system by other users, or is it inherent in the work station (disc access or computation speed)?

f. Is data relatively secure
- from accidental loss
- power failures
- malicious tampering
- communication errors
- input or processing errors
- by built-in backup and copy features?

g. Are passwords
- built-in
- user defined
- management defined
- recoverable if lost?

h. Is the system self starting at power up, or do you need to invoke job control commands?

i. Are the program functions (modules) interconnected or do you need to "run" each module separately?

j. Is the system driven by
- dialog boxes
- menu
- questions and answers
- function keys
- all of these?

k. Can you move about in the menu on the screen
- to skip questions
- to back track to correct entries?

l. Do menus (questions)
- have reasonable default values
- have range limit checking
- single keystroke response (except numbers)
- allow no response, without error (unless data is imperative)
- use CRT highlights (inverse video, under-lining, blinking) to good effect
- allow user defined defaults to be saved for future use
- have reasonable error messages
- have neat, easily read layouts
- have contents grouped in logical, rational data sets?
- have a consistent exit/quit/terminate/restart command structure

m. Can regular or sophisticated users get abbreviated menus, or change menus for custom, repetitive jobs?

n. Is the system crash-proof - i.e. can you
- recover from all numeric errors without halting the system
- accidentally hit any key without halting the program
- run the system with the defaults (as a demo) with no failures?

o. Can the system handle both English and Metric data
- by conversion of one to the other
- by flagging which is which?

p. Can data be transmitted to a central data bank easily? What hardware or software is needed?

q. Can data be transmitted or retrieved from another workstation or data base?

r. Does the system have a good audit trail (can you tell what you did, what you did it to, when you did it, who did it, etc)?

s. Is the audit trail saved? Is it part of the saved run stream to be used again? Can it be reviewed on paper or CRT? Scrolled on the CRT?

t. Are questions, answers, and menus phrased in good English? Do they make sense the first time you see them? Can they be changed by the user?

u. Does the system keep usage statistics for management review?

v. Is the update procedure automatic? Does it retain all personalized defaults and customized algorithms?

w. Is the system truly flexible and modifiable or are these just sales-words?

x. Is the upgrade path known, achievable with limited training, affordable?

y. Is maintenance path achievable with suppliers resources, affordable, reliable?

15.07 The Human Connection
People play the most vital role in a computer aided log analysis system. The supplier (in-house, service bureau, or third party vendor) will have salesmen, technical specialists, log analysts, programmers, technicians, accountants, receptionists, teachers, and maintenance personnel who will affect the success of the system.

The analyst must be able to get information, repairs, training and support from the supplier. The analyst must communicate results quickly and cost effectively to the end user, staff and management. It is the end user who must understand and ultimately make use of the data from the system.

The following people oriented checklist will help reduce the chance of failure of a computer aided system:
1. The Supplier
a. Will the software supplier be around next next year?
b. Does the supplier have an extensive installed software base?
c. Does the supplier use the software for its own consulting firm or service bureau?
d. Does the supplier appear eager to support the software? To modify it for you?
e. Is there an update or maintenance fee? How much? What do you get for it? Is it worth the price?
f. Is the documentation clear and complete?
g. Is there phone-in support by qualified staff?
h. Is the code open so you can modify it, or protected and only modified by the supplier? Is open code an extra cost item?
i. Is the price acceptable? Are add-on systems discounted?
j. Is training complete and friendly? Will all personnel be trained and for what period of time is re-training available?
k. Is training at your company or at the supplier's?
l. Are there software add-ons, related packages, other software that you want from the same supplier? Is it integrated? Is it supported uniformly?
m. Is customization available? At a reasonable cost? Quickly enough? By competent people?

2. The Analysts
a. Does the analyst understand how the system works?
b. Does the analyst understand the mathematical models and how to manipulate them? Their limitations and uses? Can he or she contribute new methods to the system?
c. Can the analyst verify and duplicate the results by other means?
d. Can the analyst handle the data flow into and from the system?
e. Can the analyst handle the staffing, budgeting, (time and money) and other administrative requirements of the system?
f. Can the analyst interpret the results and communicate results to end users? To management? To staff?
g. Can the analysis group work together as a team? Can it get the resources it needs to be effective?
h. Were the analysts involved in choosing the system? Is the system their first choice? Do they take "ownership" of the system?

3. The End Users
a. Are the end users satisfied with the system capability and performance?
b. Are they satisfied with the quality of results, numerically and visually?
c. Are the results in the right language for the purpose intended?
d. Is the turnaround time adequate for the purpose intended?
e. Is the cost commensurate with the quality of the results?
f. Do they believe the results? Do they believe the analyst's explanations?
g. Are the results actually used by the end user?
h. Can an end-user run the system if necessary?
i. Is the end user aware of all the features available on the system? Will they all be used?

4. Management
a. Does management support and understand the uses, costs, infrastructure needed for the system?
b. Does management really want the work done?

15.08 Computer Aided Log Analysis System Costs
The cost of a computer aided log analysis system will vary dramatically, depending on its performance, mode of operation, and relationship to other in-house information systems.

The less the system does, the lower the cost should be. A single work station (terminal or desktop, with or without central data base) should allow the user to do foot by foot analysis of 3 to 8 zones of interest (200 to 1000 feet) per day, for between $0.50 and $1.50 per foot. The process sequence should include data entry, edit, parameter entry, raw data plot back, computation, re-computation as necessary, rough plots, final plots, final print-outs and summary data print outs.

Systems with lower cost and lower productivity have a place in small organizations that have a few zones per week to analyze. For example, a Basic language portable computer with a miniature plotter can be purchased for under $300. Such a system can do an adequate single point analysis, as can spreadsheet programs like Excel or Lotus 1-2-3 on small home or office computers (see Chapter Fourteen). Both options require some programming by the user.

Higher costs are associated with higher degrees of integration of systems, such as ties to mapping, cross section, seismic, or engineering modules.

Software and hardware costs will be noticeably higher for a geological well data system or engineering and production data system that communicates with the log data base and the log analyst. Systems with extensive data management and graphics capabilities have cost over $1,000,000 even in recent years.

A typical desktop system with one work station will cost between $5,000 and $80,000 for hardware and software. Systems based on home computers could be assembled for less than $2,000. A shared resource desktop system could cost $250,000 for five complete work stations and a central data store (with multi-user software licenses).

Systems with terminals to a UNIX mainframe seldom cost less than $90,000 to $120,000 for the mainframe, plus $2,000 to $5,000 per work station. If a mainframe computer with sufficient capacity exists, it may be less expensive to add on terminals than to purchase desktop computers. If the computer needs enhancements such as additional disc storage, memory, or communications channels to handle the log analysis system, these costs should be added to the price.

Corporate infrastructure costs are important considerations. Space, personnel, management, specialized supplies, telecommunications, installation, start-up, training, and re-training are real and significant costs. They must be included in estimating the cost per foot of analysis.

15.09 A Review of Commercially Available Systems
A relatively large number of computer-aided log analysis systems have been presented for public use over the last 30 years. Some, such as Saraband, were used extensively for more than 20 years and many examples are found in well files.

The systems can be grouped into five categories:
1. Oil company in-house systems, whether or not available for sale or leased commercially.
2. Logging service company truck borne wellsite systems.
3. Logging service company computer center systems.
4. Service bureau, time share, or consulting firm services.
5. Third party vendors who supply in-house systems on either a sale or license arrangement.

Table 15.01 reviews the majority of systems that have been offered - many are now obsolete or unsupported. A review of advertisements in the well-logging literature will reveal the current favorites. The material in Table 15.01 was taken from published technical papers or brochures. Errors or omissions may occur in the listing due to the introduction of new systems and upgrading of capabilities. I'll update this table as time permits.