CHAPTER TWELVE: CASE HISTORIES

Table of Contents
12.00 Introduction to This Chapter
12.01 Shaly Sand
12.02 Mixed Lithology
12.03 Carbonate Reservoir
12.04 Granite Reservoir
12.05 Fractured Reservoir
12.06 Tar Sand
12.07 Horizontal Wells
12.08 In Conclusion
12.09 Exercises For Chapter Twelve
12.10 Bibliography For Chapter Twelve

View old version of Chapter Twelve
Fractured Reservoir Case Histories
Arctic Islands Case Histories

Continue to Chapter Thirteen

Publication History: This Chapter contains entirely new material compared to the original textbook. Explanations are more informative and illustrations are more modern. Originally published in 1991 as part of Chapter Eight of The Log Analysis Handbook – Volume Two (self published).These case histories are also contained in Crain’s Petrophysical Pocket Pal. The old version of Chapter Twelve is still very informative and contains many varied case histories worthy of study.

CHAPTER TWELVE: CASE HISTORIES

12.00 Introduction to This Chapter
Studying case histories is a good way to learn log analysis. Reading technical papers, especially those with good examples, is another way to see what can be done. The case histories presented here cover a range of problems encountered in the real world. Every job has its unique problems and requirements, so these examples just scratch the surface of what can be presented to the analyst.

When you analyze the logs on any well, or group of wells, you must learn all there is to know about the wells or offset wells before you start the job. You also must check your work against ground truth before you finish the job. Well history printouts, formation tops, sample and core descriptions, core analysis results, and perforated intervals, production history, and test information are the first clues that help narrow the zones of interest. Reconciling all available data is a requirement, not an accident. The integration of all scientific disciplines is now the norm, not the exception. Petrophysics is more than mere log analysis data processing.

If you are using this book for self directed study, I recommend you read the commentary for each case, then calculate a reasonable log analysis for each. Compare your answers and conclusions to the listings and depth plots that are presented. Adjust your assumptions or check your arithmetic if you get grossly different results. Draw your own conclusions about the zones.

I don’t claim that these example analyses are perfect or unambiguous. Each analyst will get slightly different results and interpret them differently.

12.01 Cretaceous Shaly Sand
The raw logs show two zones of interest: a lower clean sand with hydrocarbon over water and a very poor quality upper shaly zone with a hydrocarbon indication. These zones can be spotted by laying the density log over the resistivity log and looking for the crossover of the curves. Because the sands are not pure quartz, a conventional shaly sand analysis technique is not appropriate because it would underestimate porosity, so a complex lithology model was used instead.

There is no density neutron cross over in the clean sand, so this zone is oil bearing. We cannot tell about the upper shaly sand because the shale effect masks any possible gas effect. After shale corrections, the density and neutron still do not cross over, so oil is most likely.

The water zone at the base of the clean sand provides water resistivity information for use throughout the rest of the zone. Core data was available to calibrate porosity and permeability results. The answer plot shows the results of the lithology, porosity, and hydrocarbon analysis.

The raw data plot shows two interesting features: the flat SP compared to GR in tight zones and the SP excess at 3400 feet, indicating better permeability than the rest of the shaly sand. The lithology track on the answer plot shows this interval to be more sandy and less limy than the rest of the shaly sand.

FIGURE 12.01: Raw logs for Shaly Sand Example

FIGURE 12.02: Raw logs showing shale baselines

The following crossplots were made:

1. Porosity vs Resistivity - shows water saturation lines (shale data falls below 100% Sw line).

2. Porosity vs Saturation - shows constant water volume lines. Data streaming above and to the right indicate transition and water zones. Shale data falls to the bottom of the graph.

3. Density vs Neutron - shows all data below limestone line, indicating either no perfectly clean sand or mixed lithology sand (GR suggests clean sand). Shale data falls towards bottom and right.

4. Core porosity vs core permeability - shows a data cluster which cannot be used to derive a regression line mathematically. A line drawn thru the lower left corner will work fine.

FIGURE 12.03: Basic crossplots for Shaly Sand Example - Part 1

5. Matrix density vs matrix cross section - confirms that sand is not pure quartz, but the plot does not tell us which minerals to expect. Sample description suggests quartz, calcite, and glauconite (plots past anhydrite at top right).

6. Apparent water resistivity vs density - shows RW@FT and RWSH points relative to spread of data for both shale and hydrocarbon zones.

7. Apparent water resistivity vs density porosity - similar to above but uses effective porosity. Shale plots near origin, water zone at top left, oil at right.

8. Apparent water resistivity vs gamma ray - shows where to pick GR0 and GR100 (also can be picked from raw logs). Best oil zone is off scale to the right.

FIGURE 12.04: Basic crossplots for Shaly Sand Example - Part 2

Just to illustrate that you don't need a $5000 to $75000 log analysis package to do good work, all the calculations and crossplots shown here were made with a Lotus 1-2-3 spreadsheet program, called META/LOG, written by the author, and available for a mere $50. The depth plot shown below was made with a $50.00 shareware plot utility called LAS/PLOT. This presentation is the bare minimum that would be given; more complete plots are shown in the next two case histories. Most log analysis packages can make similar or more elaborate plots.

FIGURE 12.05: Basic depth plot for Shaly Sand Example

Reports and data listings are an essential part of log analysis. The next illustration shows the answer report prepared automatically by META/LOG after the analyst has finalized the job. The hydrocarbon summary page shows a comparison with core. The match between porosity and permeability are extremely good, as they should be.

FIGURE 12.06: Basic answers and raw data listings for Shaly Sand Example

A scan of the Rwa column shows the RW @ FT in the water zone to be 0.17 ohm-m. Reserves and productivity are useful by-products of this analysis. For example, estimated productivity for the upper shaly sand is only 0.6 barrels per day compared to 231 for the clean sand. The shaly sand would be uneconomic anywhere, but an exploration play may be developed to find cleaner sands nearby.

FIGURE 12.07: Summary log and core data listings for Shaly Sand Example

When you analyze the logs on any well, or group of wells, you must learn all there is to know about the wells or offset wells before you start the job. You also must check your work against ground truth before you finish the job. Below is a copy of the well history printout for this case history. Formation tops, cored and perforated intervals, and test information are the first clues that help narrow the zones of interest.

FIGURE 12.08: Well history listing for Shaly Sand Example

Core data is an important ingredient in testing your results against ground truth. Check your results and those shown above against the core listing shown below.

FIGURE 12.09: Core data listing for Shaly Sand Example (but see next illustration)

The average porosity is 25.3% and average permeability is 624 md. The porosity is higher than the log analysis shown earlier and the log results could be made to match the core by reducing shale volume or shifting the density porosity to a higher value. This would be an arbitrary calibration shift as there is no evidence that the log is mis-calibrated. Some one may have noticed this problem at some stage because a second core analysis listing is available, dated several years after the first one. The re-analysis is shown below.

FIGURE 12.10: Re-analyzed core data listings for Shaly Sand Example

Notice that the average porosity is 22.6% instead of 25.3%, much closer to the original log analysis. Permeability has changed only slightly from the first core analysis. The moral of the story is that core analysis is not perfect and some errors should be expected. Checking log analysis in several cored wells is the only way to find the odd bad core or bad log.

12.02 Triassic Dolomitic Sand
This example is sandstone with complex mineralogy. The porosity resistivity overlay will help find the zone of interest but the high resistivity of the anhydrite cap and lower shale may be confusing at first. Some people like simple rules for defining pay zones, such as a resistivity cutoff. This would not work in this case, or in many other situations either. The SP also suffers badly from the high resistivity.

FIGURE 12.11: Raw log and core data depth plots for Dolomitic Sand Example

Notice the very close comparison between the core porosity (squared line) and log analysis porosity (smooth line) on the computed log analysis depth plot shown above.

FIGURE 12.12: Crossplots for Dolomitic Sand Example

Crossplots help define the lithology and the lack of a water or transition zone.

1. Porosity vs Resistivity - shows no water.

2. Porosity vs Saturation - shows constant water volume lines. Data follows one hyperbolic line - no transition or water zones. Shale data falls to the bottom of the graph.

3. Density vs Neutron - shows all data below sandstone line, indicating either no perfectly clean and or mixed lithology sand (GR suggests clean sand). Shale data falls towards bottom and right.

4. Core porosity vs core permeability - shows a data distribution that can be used to derive a regression line mathematically.

A plot of the computed results is shown below. Notice the complex lithology throughout the interval. Using a simplified quicklook analysis can result in a porosity that is 4% too low - a 25% error in this low porosity environment.

FIGURE 12.13: Depth plot for Dolomitic Sand Example

The listings for final results and hydrocarbon summary are shown below. The log analysis porosity is a little low compared to core and could be increased to match core analysis better by adjusting the target DENSMA parameter in the META/LOG program.

FIGURE 12.14: Results and raw data for Dolomitic Sand Example

This is a thin bed problem as much as a heavy mineral problem, so data in the porous interval must be picked at very close intervals. The “peaks and valleys” rule applies. Any form of averaging the data will mask the contribution of the central porous “hot spot”. Ninety percent of the productivity comes from this 1.5 meter interval (2056.5 -2058.0 meters).

FIGURE 12.15: Summary results of log and core data for Dolomitic Sand Example

Below are the well history and core data for this well. Note that the perforated interval listed on the well history is not across the best porosity. This may have been a transcription error as it appears to be 10 meters deeper than it should be. Database contents are not perfect either.

FIGURE 12.16: Well history listing for Dolomitic Sand Example

Compare your results with this core data, especially in the thin high porosity streak 2056.8 to 2058 meters. You will also have to adjust the CPERM parameter in the permeability equation to get a good match to core. Note that a conventional shaly sand analysis will under-estimate porosity by as much as 4% porosity, so the only correct approach is the shale corrected complex lithology model recommended in this book. If heavy minerals are not a problem, the complex lithology model works just as well as the shaly sand model, so there is no reason to ever use the shaly sand approach.

FIGURE 12.17: Core data listing for Dolomitic Sand Example

12.03 Devonian Carbonate Reef
This example is more complex than first appearances would indicate. Initially, the resistivity and porosity logs show a 70 meter pay zone, but study of tests, production history, and workover history on this and adjacent wells paint a different story. Water break through has begun in the lower portion, defined by lower resistivity values at 2158, 2166, and 2173 meters.

FIGURE 12.18: Raw data for Carbonate Reef Example - Part 1

The extra high resistivity from 2108 to 2115 meters is a gas cap with solvent over ride, and very high GOR is found down to 2125 meters. Since production rates are severely penalized by government regulations when GOR is too high, this interval cannot be completed, leaving only a short interval between 2125 and 2155 meters available for production.

FIGURE 12.19: Raw data for Carbonate Reef Example - Part 2

The PE curve indicates clean dolomite, while the density neutron shows little separation for dolomite in the gas zone at the top. The raw logs indicate limestone with 8 % porosity when the zone is really dolomite with 13 % porosity. This is caused by gas effect canceling the dolomite effect. Porosity must be computed from the special "Gas in Heavy Minerals" algorithm over this interval or the results will be far too pessimistic. Many computer aided log analysis programs cannot do this without some help from you.

Beware of underestimating porosity in the “Gas in Dolomite” environment. Although visual observation would provide good porosity values in the oil and water zones, it is completely inadequate in the gas and solvent zones.

A depth plot of the density neutron log on a dolomite scale helps point this out by creating the gas crossover effect. Beware of dolomite scales in a limestone rock - the crossover on the density neutron DOES NOT indicate gas in this situation. Some very expensive mistakes have been made by inappropriate use of dolomite scale logs.

There is also a small amount of crossover on the dolomite scale log in the oil zone caused by the light gravity crude. Notice that there is no crossover in the water zone, demonstrating that the dolomite scaling is correct.

FIGURE 12.20: Depth plot of results for Carbonate Reef Example

Although not shown on any of the depth plots, the porosity from the sonic log would be very optimistic in some levels, caused by cycle skipping in fractured rock. In other levels, the porosity would be several percent too low due to the sonic's inability to see all vuggy porosity. These observations indicate how difficult it is to analyze older wells where the sonic may be the only porosity log.

Fractures are indicated by skips on the sonic log and spikes on the density log. These are also the most likely places for water break through. The lithology crossplots show the effect of vugs, fractures, and gas on the sonic log, as well as confirm the dolomite lithology. Some of the density spikes caused by hole breakout at fractures still show up on the final results. These could have been edited to reflect reservoir conditions instead of borehole effects

FIGURE 12.21: Results listing for Carbonate Reef Example, showing gas over oil over water, and possible water breakthrough zones at fractures

Below are the well history and core data for this well. A detailed match to porosity from core is usually not possible due to heterogeneity of the reservoir and the difference in volume of rock seen by logs compared to the core. A good match to average porosity and total pore volume can be achieved by adjusting the target matrix density in the computer program. A match to matrix permeability may be possible if pore geometry is uniform throughout the interval. Heterogeneity and vuggy porosity often prevent a reasonable permeability from log analysis. Fracture permeability seen on the core plugs cannot be quantified by conventional log analysis accurately without a lot of iteration. This topic is covered in Chapter Twenty-Nine.

FIGURE 12.22: Well history listing for Carbonate Reef Example,

FIGURE 12.23: Core data listing for Carbonate Reef Example,

Notice the high permeability streaks caused by fractures. Vuggy porosity is mentioned often, suggesting that it would be difficult to match permeability from log analysis with core data.

12.04 Granite Reservoir
Most people forget that there are many unconventional reservoirs in the world, including igneous, metamorphic, and volcanic rocks. Granite reservoirs are prolific in Viet Nam, Libya, and Indonesia. Lesser known granite reservoirs exist in Venezuela, United States, Russia, and elsewhere. Indonesia is blessed with a combination sedimentary, metamorphic, and granite reservoir with a single gas leg. Japan boasts a variety of volcanic reservoirs.

Log analysis in these reservoirs requires good geological input as to mineralogy, oil or gas shows, and porosity. A good coring and sample description program is essential, and production tests are a essential. The analyst often has to separate ineffective (disconnected vugs) from effective porosity and account for fracture porosity and permeability. All the usual mineral identification crossplots are useful but the mineral mix may be very different than normal reservoirs. Many such reservoirs seem to have no water zone and most have unusual electrical properties (A, M, N), so capillary pressure data is usually needed to calibrate water saturation.

Figure 12.24: Ternary Diagram for Granite

In the example below, the mineral assemblage was defined by the ternary diagram (Figure 12.24). The three minerals (quartz, feldspar, and plagioclase) were computed from a modified Mlith vs Nlith model, in which PE was substituted for PHIN in the Nlith equation. If data fell too far outside the triangle, mica was exchanged for the quartz (Figure 12.25).

Three rock types, granite, diorite, and monzonite, were derived from the three minerals. A trigger was set to detect basalt intrusions. A sample crossplot shows how the lithology model effectively separates the minerals.

FIGURE 12.25: Mlith vs Plith crossplot for granite (micaceous data excluded)

A sample of the log analysis plot is shown below. The average porosity from core and logs is only 0.018 (1.8%) and matrix permeability is only 0.05 md. However, solution porosity related to fractures can reach 17% and permeability can easily reach higher than several Darcies. Customized formulae were devised to estimate these properties from logs based on core and test data. My colleague Bill Clow devised most of the methods used on this project.

FIGURE 12.26: Depth plot for a granite reservoir

Note the fracture porosity and permeability derived from open hole log data. Fracture porosity from resistivity micro scanner logs was also computed where available to help control the open hole work. A black and white resistivity image log (Figure 12.27) shows some of the fractures. Both high and low angle fractures co-exist.

FIGURE 12.27: Resistivity micro scanner image in granite reservoir

It is clear that non-conventional reservoirs may need some extra effort, customized models, and unique presentations. Everything you need to develop these techniques can be found in Chapters Six through Eleven in this Handbook. Further information on fractured reservoirs is covered in Chapters Twenty-Eight through Thirty.

Here is a granite/metamorphic example. In this case, the mineralogy was triggered by quantitative sample descriptions, which in turn were keyed to raw log response to minimize cavings and depth control issues.

FIGURE 12.28: Metamorphic / Granite example.

Quantitative sample description of mineral composition is shown in track five (right-hand track). Interpreted lithology is in track four; computed porosity in track three (middle track). The log analysis porosity matches core reasonably well (center track) and open hole fracture indicators (right edge of track one) correspond to resistivity image log data (left edge of track two).

12.05 Fractured Reservoir
Go to Chapter Twenty-Eight Case Histories.

12.06 Tar Sand
Analysis of tar sands and bitumen zones follows all the usual methods for normal oil and gas, with only minor differences. One is the presentation of data listings and depth plots in weight fraction (or weight percent) instead of, or in addition to, volume fraction as in the example below.

FIGURE 12.29: Tar Sand Example, Alberta

Due to the higher density of bitumen than conventional oil, it is not unusual to find water over oil, as shown here. Knowing the location of the water-oil contact is critical in steam assisted gravity drainage (SAGD) operations as heat lost to the water zone is waste energy, and heat rises. See Chapter Ten for details about the math for weight fraction calculations.

12.07 Horizontal Wells
Many horizontal wells are not logged at all. Some have only a gamma ray log measured while drilling. A few have a more or less complete suite of logs measured while drilling or logged on drill pipe or on coiled tubing. The examples shown here had no logs in the horizontal well, but each had very close spaced (160 acre) vertical wells to define the geology. Even though there was lots of control these horizontal wells were failures because the structural situation of the target zone was not recognized before the wells were drilled.

In the first case, a horizontal well was planned for the thick pay sand shown in the well on the right hand side of Figure 12.30. After penetrating the coal, the well was directed to the left and encountered the shale and poor quality sand and never reached the good sand. The oil-water contact shows that the wells are displayed at there correct structural depth.

So why was the horizontal well drilled here? Although no one admitted it, I suspect that no structural cross sections or maps were made, and the play was based on stratigraphic correlation. After all, everyone knows that the prairies are flat, right? Had the well been drilled near the center of this cross section and aimed in the right direction, a successful well would have been more likely.

FIGURE 12.30: Structural Section, Alberta

This client drilled three other plays in widely separated regions with similar poor results caused by similar structural problems. Good forensic log analysis answered the question about the failures. A good integrated study before drilling would have saved a lot of money.

No horizontal well was ever drilled on this next example, and you can see why. The sand channel in the middle of the field was not found until 25 years after the initial. pool development. Attempts to unitize always failed because no one could agree on the geology or engineering data that showed a significant pressure and productivity difference between the east and west sides of the pool. The sand channel well was drilled based on 3-D seismic, but the operator still believed he was drilling a good porosity carbonate until the sand chips started to appear at the sample catcher.

FIGURE 12.31: Structural Section, Alberta

Because of the structural relief and varied lithology, drilling a horizontal well here might be quite risky. However, if the orientation of the channel can be identified, this might be a good target. Was a dipmeter run? 'Fraid not.

12.08 In Conclusion
The case histories here and elsewhere in this Handbook are intended to show style and hint at procedures you might incorporate in your own work. Every analysis can be improved, including these examples. Study of the case histories in the Bibliography will enhance your ability to work all areas of the world. Research is the key to a successful career in petrophysics.

12.09 Exercises For Chapter Twelve
1. Prepare a numerical log analysis for each of the case histories in Sections 12.01, 12.02, and 12.03. Write a two page report for each covering introduction, available data, method, results, conclusions, and recommendations. (100 marks)

12.10 Bibliography For Chapter Twelve
A. AFRICA

1. Niger Delta SWSC WEC Nigeria, 1966

2. Introduction to a Review of Log Interpretation Methods Used in the Niger Delta. A. Poupon, I. Strecker, J. Gartner SPWLA, 1967

3. A Review of Log Interpretation Methods Used in the Niger Delta A. Poupon, I. Strecker, J. Gartner SPWLA, 1967

4. Role Of Reflection Seismic In Development of Nembe Creek Field, Nigeria. P.H.H. Nelson AAPG, 1977

5. Hydrocarbon Habitat of Tertiary Niger Delta B. Evamy, J. Haremboure, P. Kamerling, W. Knaap AAPG, 1978

6. Petroleum Geology of the Niger Delta K. Weber, E. Daukoru Shell-BP, Nigeria

7. Well Evaluation Conference - Nigeria SWSC WEC, 1974

8. The Etosha Basin Reexamined (S.W. Africa) J.A. Momper OGJ, 1982

B. ASIA

1. Logging Methods in Japan H. Sato SPWLA, 1968

2. The Status of Well Log Interpretation in India S. Itenberg, J. Koithara, K.H. Hashmy SPWLA, 1969

3. Outline of Sedimentary Geology of Maine Oil-Basinal Areas in Indonesia. A. Pulunggono, P.N. Pertamina WEC Indonesia, 1971

4. Chinese Bottlenecks Far Eastern Economic Review China, 1972

5. Formation Evaluation in Indonesia C. Dadrian, H. Brown, J. Geotz, B. Marchette SPWLA, 1973

6. Eastern Asia Coasts Offshore Are Promising Petroleum Frontiers A.A. Meyerhoff OGJ, 1976

7. Soviet Oil Flow Up, But Signs of Trouble Multiply OGJ, 1977

8. Log Interpretation in Malay Basin K. Kuttan, C. Stockbridge, H. Crocker, J. Rembry

9. Bangladesh: A Brief Account of Geology and Hydrocarbon Exploration. M. Maroof Khan OGJ, 1981

10. Geology of Offshore Northwest Palawan, Philippines -1 Dr. A. Saldivar-Sali, Dr. H.G. Oesterle, D. Brownlee OGJ, 1981

11. Review of the Results of Some Petrophysical Studies on Cores From Assam Oil Fields, India J. Koithora, J.S. Bisht, U.V.S. Nohwar SPWLA, 1973

12. Role of Integrated Study of Core and Log Analysis in Realistic Estimation of Reserves of L-III Horizon of Bombay High Fields D.K. Gupta, S.K. Sharma, R. Dalavi, H. Raj SPWLA, 1981

13. Geophysical Well Logging in the Soviet Union G.V. Keller SPWLA, 1966

14. Computer Processed Interpretation WEC Indonesia, 1970

15. Water Injection in China: Waterflooding the Oil Reservoirs of China. Lin Zhifang OGJ Report, 1982

C. AUSTRALIA - NEW ZEALAND

1. Formation Evaluation in Australia H. Crocker, I. Strecker SPWLA, 1968

2. Geology and Mineral Deposits - Australian National Government Publication, 1969

3. Exploration Results Off South New Zealand R. Sanford OGJ, 1980

4. Australia's Northwest Shelf: Gas is the Current Attraction J.S. Thomas, E.O. Nextvold, A. Crastella WO, 1978

5. Antarctica - Operating Conditions and Petroleum Prospects L.F. Ivanhoe OGJ, 1980

6. The Definition of Development of the Mackerel Field, Gippsland Basin. D.M. Maughan, A. Mebberson, D. Morton OGJ, 1981

7. Australia's Amadeus Basin Has Cambro-Ordovican Potential D. Casey, J. Harrison WO, 1981

8. Bass Basin Set for New Exploration O.D. Weaver, Y. Houde, J. Downing, J. Smitherman, C. Nettels OGJ, 1982

D. EUROPE

1. Logging and Perforating in W.W. Germany H.W. Sorber SPWLA, 1966

2. Logging Problems in the North Sea A. Misk, A. Poupon

3. A Review of the Status of the Basic Well Logging and Interpretation Methods Applied in Hungary
Z. Barlai, I. Czegledi, P. Muller SPWLA, 1973

4. How Oxy's Log Program Evaluation Piper OGJ, 1975

5. Logging Programs and Log Analysis Techniques for Norwegian North Sea Wells. C.R. Glanville, F. 6. Millard, B.E. Morgan The Log Analyst, 1977

7. Geology of the North Seas SWSC, WEC, 1974

8. A Log Analysis Method for Ekofisk Field, Norway J.D. Owen SPWLA, 1972

9. Jurassic Sandstone Reservoirs SWSC WEC, 1974

10. Lower Tertiary and Upper Cretaceous Carbonates SWSC WEC, 1974

11. Paleocene Sandstones SWSC WEC, 1974

12. Computer Processed Interpretation of the Rotliegendes Formation WEC, 1974

13. Formation Evaluation in Jurassic Sandstones, in the Northern North Sea Area. G. Hodson, W.H. Fertl, G.W. Hammack SPWLA, 1975

14. New Log Data Give Better North Sea Well Completions G.M. Hodson, W.H. Fertl, G.W. Hammack World Oil, 1975

E. MIDDLE EAST

1. Outline of Southeastern Middle East Stratigraphy E. Hart SWSC WEC Middle East, 1967

2. Well Logging in the Middle Eastern and Similar Large Reservoirs P. Threadgold SPWLA, 1967

3. Outline of Sedimentary Geology of Libya SWSC WEC Libya, 1970

4. Egypt's Petroleum Geology: Good Ground For Optimism A.S. Abdine World Oil, 1981

5. On the Problem and Some Results of Well-Logging and Surface Geophysical Survey in the Petroleum Prospecting on the Karia Ba Mohamed Area, Morocco. S. Demnati, J. Frydecki, A. Kulikowski, E. Nowicka SPWLA, 1980

6. Complex Lithology SWSC WEC Libya, 1970

7. Shaly Sands SWSC WEC Libya, 1970

8. Field Studies SWSC WEC Arabia, 1975 Iran, 1976

9. Evaluation of Middle East Reservoirs with Complex Lithology D.E. Barid SPWLA, 1968

F. SOUTH AMERICA

1. Log Interpretation in Bolivia H.A. Salisch, H. D. Brown SPWLA, 1966

2. Logging Programs in Northeastern South America H.B. Brown, H.A. Salisch SPWLA, 1971

3. South Lake Maracaibo Log Analysis H.D. Brown, J.D. Cunningham, H.A. Salisch SPWLA, 1971

4. Argentina Offers Something for Everyone J.J. Stewart-Gordon World Oil, 1980

5. Porosity and Lithology Determination With Logs in the Caimancito Field, Jujuy Province, Argentina. SPWLA, 1976

6. The Dual Spacing Neutron Log (CNL) in Venezuela J.E. Hung, H.A. Salisch SPWLA, 1972

7. Giant Fields in Southeast Mexico OGJ, 1981

8. Petroleum Geolog of Trinidad and Tobago. P.R. Woodside OJG, 1981

9. Falklands Seem Attractive Wildcat Target J.C. McCaslin OGJ, 1982

10. Commercially Prospective Oil Accumulation in the Fractured Basement Complex of the Hama Area of the Orinoco Petroliferous Belt, Eastern Venezuela. D. Flores. CWLS, 1981

11. Log Evaluation of Tuffites and Tuffaceous Sandstones in Southern Argentina. A. Khatchikian, P. Lesta. SPWLA, 1973

G. TAR SANDS AND HEAVY OIL

1. Formation Evaluation in Heavy Oil Sands J.S. Brown SPWLA, 1966

2. Petrophysical Mapping of the Wabiscaw Sand, Marten Hills Area, Alberta. J.T. McCoy, E.J. Burge SPWLA, 1976

3. Well Logs Evaluate and Monitor Heavy Oil Steamflood in Kern County, California. C. Rowx, W.H. Fertl, E. Frost, D. Stedman, D. Elliot CWLS, 1981

4. How a Texas Heavy Oil Prospect Was Evaluated R. Freedman, J.R. Studlick Technology, 1981

5. Mineable Oil Sands Limits Surface Facility Locations R.B. Dunbar, R.A. Funk, B. D. Prasad 1980

6. Well Log Analysis in Heavy Oil Sands B. Cossett CWLS, 1981

7. Commercially Prospective Heavy Oil Accumulation in the Basement Complex of the Hamaco Area of Orinoco Belt, Eastern Venezuela D. Flores, S.P. Meneven SPWLA, 1981

8. Evaluation of a Heavy Oil Prospect Banderea Tan Area- Maverick and Zavala Counties, Texas. R. Freedman, J. Studlick SPWLA, 1981

9. The Cold Lake Project: A Report to the Energy Conservation Board Imperial Oil Limited, 1978

10. Sediment-Geological Study of a Steam-Drive Project in the Deltaic River Sands. C. Kruit, S. Maraven 1978

11. Evaluation of the Albert Tar Sands R.C. Sah, A.E. Chase, L.E. Wells AIME, 1974

12. Measurement of Petrophysical Properties of Unconsolidated Sand Cores. B.F. Swanson, E.C. Thomas SPWLA, 1980

13. Log-Core Correlations in the Athabasca Oil Sands N.N. Collins SPE, 1976

14. Tar Sands Core Analysis Versus Log Analysis Controversy - Does It Really Matter. R.W. Zwicky, J.R. Eade CWLS, 1977

15. Round Robin Study of Analytical Procedures of Various Laboratories on Assay Analysis of Athabasca Tar Sands. J.R. Eade CWLS, 1975

16. Importance of Reservoir Description in Evaluating In-Situ Recovery Method for Cold Lake Heavy Oil. G.H. Kendall JCPT, 1977

17. Athabasca Tar Sand Reservoir Properties Derived From Cores and Logs. R. Woodhouse CWLS, 1976

18. Log Evaluation and Monitoring of a Unique Heavy Oil Reservoir Project, Alberta Canada
P. Campbell, M. Cucheck, E. Forst, W.H. Fertl CIMM, 1982

19. Athabasca Oil Sand Evaluation Using Core and Log Analysis and Ocological Data Processing Methods. R.W. Fetzner, W.L. Henson, F.J. Feigl SPWLA, 1966

20. Sample Disturbance in Athabasca Oil Sand M.B. Dusseault JCPT, 1980

21. Errors in Core Oil Content Data Measured by the Retat Distillation Method. J.J. Rathmell SPE, 1966

22. Core Analysis of Unconsolidated and Friable Sands C.C. Mattax, R.M. McKinley, A.T. Clothier JPT, 1975

H. TIGHT GAS

1. Log Analysis in Tight Gas Sands - A Reconnaissance Study G.E. Dawson-Grove CWLS, 1979

2. Exploration - CanHunter Style Oilweek, 1978

3. Canada's Deep Basin: Is It a Major New Gas Province? J.A. Masters World Oil, 1978

4. Deep Basin Gas Trap - Western Canada J.A. Masters AAPG Bulletin, 1978

5. The Time-Economics of Developing Low-Grade Petroleum Deposits G.E. Dawson-Grove SPWLA, 1979

6. Gas Recovery From Tight Formations V.A. Kuusdraa, J.P. Brashear SPE, 1979

7. Mitchell Energy Foam Fracs Tight Gas Zones W.B. Bleakley PEI, 1980

8. Gas-Price Effect on Exploration Drilling Studied K. McConnell OGJ, 1981

9. An Update on Federal Tight Sands Incentive Policies World Oil, 1980

10. NPC Sees Big Potential for U.S. Tight Gas OGJ, 1980

11. Analyses of an Elmworth Hydraulic Fracture R.E. Wyman, S.A. Holditch, P.L. Randolph SPE, 1979

12. Development of Shallow Gas Reserves in Low Permeability Reservoirs of Late Cretaceous Age. G.L. Nyudegger, D.D. Rice, C.A. Brown SPE, 1979

13. Formation Evaluation and Gas Detection in Shallow, Low-Permeability Shaly Sands of the Northern Great Plains Province G.C. Kukal SPE, 1979

14. Gas Reservoirs, Deep Basin, Western Canada G.E. McMaster JCPT, 1981

15. Log Evaluation Results in the Deep Basin Areas of Alberta E.R. Crain CWLS, 1981

16. Stimulating the Triassic Carbonates in the Foothills Gas Trend of Northeast British Columbia. R.P. Wade, K. Aziz Technology, 1981

17. Evaluating and Logging Tight Rocks of South Texas T.H. Fett World Oil, 1980

18. Evaluation of Shaly Sands With Low Deliverability D.E. Cannon CIMM, 1973

19. How Technology and Price Affect U.S. Tight Gas Potential Part 2 - Economics of Tight Gas Production R.W. Veatch, Jr., O. Baker Petroleum Engineer, April 1983

20. Calculation and Significance of Water Saturations in Low Porosity Shaly Gas Sands. M.J. Rosepiler SPWLA, 1981

I. UNITED STATES

1. Wireline Operations in the Deep Delaware Basin J.D. Cunningham, F.D. Fulkerson SPE, 1966

2. Drilling and Completion Practices in Active U.S. Areas J.P. David World Oil, 1981

3. Logging Offshore Wells in the United States R.B. Snow, W.H. Throop, J.A. Williams SPWLA, 1968

4. Logging and Evaluation High Angle Well Bores on a Large Scale Drilling and Development Program, Long Beach, California SPWLA, 1968

5. Log Evaluation of a Heterogeneous Carbonate Reservoir Cato San Andres Field. M.L. Traugott SPWLA, 1970

6. Logging in the Ellenburger - 1970 R.H. Neustaedter, A.W. Schmidt API, 1970

7. Case Histories of Subsurface Log Data Exploration Patterns in Eastern Powder River Basin. B. Jones SPWLA, 1967

8. Anomalies Observed on Well Logs G.W. Hammack, W.H. Fertl SPWLA, 1976

9. Log Analysis in the Shallow Oil Sands of the San Joaquin Valley, California. J.B. Vohs SPWLA, 1976

10. Gas Detection in Sands of High Silt-Clay Content in the Cook Inlet Area. F. Bettis SPWLA, 1977

11. Interpreting Silurian Niagaran Reefs in the Michigan Basin J.S. Labo SPWLA, 1977

12. Lithology Crossplots: Applications in an Evaporite Basin - The Maverick Basin of Southwest Texas SPWLA, 1977

13. Well Log Analysis in the Austin Chalk Trend W.D. Bishop, M.R. DeVries, W.H. Fertl SPWLA, 1977

14. A Preliminary Evaluation of Various Log Analysis Techniques for the Eastern Devonian Shales - Fractured Shales J.B. Curtis, W.G. Fingleton CWLS, 1979

15. Hydrocarbon Potential in Gulf of Alaska - What Happened? B.W. Aud OGJ, 1979

16. Upgrading Medina Gas Well Production in Western New York D. Copley World Oil, 1980

17. Toward a Rational Strategy for Oil Exploration Scientific American, 1981

18. Williston - Reviving of a Giant Oil Province. D. Hoffman OGJ, 1981

19. Operators Seek 200 BCF Gas Fields in Southern Mississippi D. Scherer World Oil, 1981

20. Unconformities - The Key To Success H. Bushnell OGJ, 1981

21. Log Evaluation Techniques in Unita Basin Found Faulty J. Osoba, R. Gist, H. Carroll World Oil, 1981

22. U.S. Atlantic Continental Margin, 1976 - 1981 R. Mattick OGJ, 1981

23. Hydrocarbon Well Logging in the Williston Basin Cross Sections of Case Histories. H. Rowe, J. McAdams, R. Mercer Continental Laboratories, 1978

24. Impact Craters: Implications for Basement Hydrocarbon Production R. Donofiro OGJ, 1981

25. Smackover Carbonate Petroleum Geology in Southwest Alabama E. Mancini, D. Benson OGJ, 1981

26. The Determination of Porosity in Sandstones and Shaly Sandstones Part One - Quality Control. J.G. Patchett, E.H. Coalson CWLS, 1979

27. Operators Charge Ahead in Overthrust Drilling W. Keener PEI, 1981

28. New Report Presents Lithologic Analysis of San Andres Formation M. C. McCaslin OGJ, 1982

29. Atokan Clastics - Depositional Environments In G. Lovelick, C.G. Massini, D.A. Kotila OGJ, 1982

30. Appalachian Gas Bearing Devonian Shales: Statements and Discussions. P.R. Potter, J.B. Maynard, W. Pryor OGJ, 1982

31. Gulf Coast Stratigraphic Traps in the Lower Cretaceous Carbonates R. Sams OGJ, 1982

32. Wattenberg Field, Paleostructure-Stratigraphic Trap, Denver Basin, Colorado. R.J. Weimer, S.A. Sonnenberg OGJ, 1982

33. Subdivision, Stratigraphy of Pre-Punta Gorda Florida Rocks (lower most Cretaceous-Jurassic)
A.V. Applegate, G.L. Winston, J.G. Palacas OGJ, 1982

34. Geology and Petroleum Potential of Alaska's Norton Basin Area M.A. Fisher, W.W. Patton, M.L. Holmes OGJ, 1982

35. A Look at Lower Tuscaloosa Petroleum potential in S.W. Alabama E. Mancini, J.W. Payne OGJ, 1982

36. Drilling and Completion Practices in Active U.S. Areas World Oil, 1982

37. Formation Evaluation in the Texas Cretaceous Chalk Trend E. Frost, D. Stedman, W. Fertl World Oil, 1982

38. How to Drill and Complete Austin Chalk Wells C. Coffman PEI, 1982

39. Comparison of Log and Core Results for an Extremely Heterogeneous Carbonate Reservoir. L.C. Marchent, E.J. White SPWLA, 1968

40. Preplatform Exploration of High Island Blocks A-560 and A-561 J.W. Lund, J.S. King, R. Berlitz, J.A. Gilreath OGJ, 1979

41. Log Evaluation of a Fractured Reservoir Monterey Shale D.E. Cannon

42. Computerized Log Analysis for Efficiently Evaluating Gas Wells and Gas Storage Reservoirs
A.W. Schmidt, D.H. Tinch, B. Carpenter, W.R. Hoyle SPWLA, 1967

43. Log Evaluation of Deep Ellenburger gas zones R.H. Neustaedter SPE AIME, 1968

44. East Cameron Block 270, A Pleistocene Field D.S. Holland, C.E. Sutley, R.E. Berlitz, J.A. Gilreath SPWLA, 1970

45. Evaluation of Hosston and Cotton Valley Fine Grained Sandstones J.M. Forgotson, J.M. Forgotson, Jr. SPWLA, 1974

46. Computer Caliper, Fingerprints of the hole, From Austin Chalk to Ellenburger. H.W. Kading SPWLA, 1977

47. Computer Log Analysis Pulse Core Analysis Equals Improved Formation Evaluation in West Howard-Glassock Unit D.A. Wilson, W.M. Hensel SPE, 1978

48. What to Expect When Logging the Cotton Valley Trend P. Nangle, W. Ferti, E. Frost World Oil, 1982

49. Waveland Field: Analyses of Facies, Diagenesis, and Hydrodynamics in Mooringsport Reservoirs. L.R. Baria OGJ, 1982

50. Nature of Porosity in Tuscarora Sandstone (Lower Silurian) in the Appalachian Basin. W.A. Wescott OGJ, 1982

51. Anadarko Shows Unique Problems, Economics J.K. Drisdale OGJ, 1982
52. Economics of Austin Chalk Production S.A. Holditch, D.E. Lancaster OGJ, 1982

53. Pressure Build Up Characteristics in Austin Chalk Wells E. Claycomb OGJ, 1982

54. Depth Porosity Relationships of the Anadorko Basin R.A. Hefner PE, 1980

55. Electrical Resistivity of Modern Reef Sediments From Midway Atoll G.V. Keller SPWLA, 1969

56. Petrophysical Evaluation of the Diatomite Formation of the Lost Hills Field, California. I.J. Stosur, A. David JPT, 1976

J. CANADA

1. A Guide to Improved Formation Evaluation in Carbonates of Northwest Alberta. A.H. Dorin, A. Chase, A. Linke SPWLA, 1965

2. Logging Oddities CWLS, 1970

3. Formation Oddities and Their Response on Wire-Line Logs J.T. Costello CWLS, 1968

4. Logging Oddities - Radioactive Clean Dolomite CWLS, 1971

5. TheTwo That Nearly Got Away - But Didn't G.E. Dawson-Grove CWLS, 1972

6. Second Generation Pembina Play Raises Deep Implications Across Alberta Oilweek, 1977

7. Petrophysical Evaluation Methods: Basal Quartz Formation, Manyberries Area, Alberta. B.W. Davis CWLS, 1979

8. Paleogeography and Sedimentation in the Upper Paleozoic, Eastern Canada. R.D. Howie, M.S. Barss GSC, 1974

9. Petrophysical Study of the Cardium Sand in the Pembina Field W.T. MacKenzie CWLS, 1975

10. Exploration Prospects in the Canadian Arctic Islands R.A. Menely 1976

11. Correlation of Producing Formations in the Sverdrup Basin D. Henao-Londono 1976

12. Arctic Islands Potential Should Justify High Costs F.G. Rayer WO, 1979

13. Hamilton Cherhill: A Case History J.R.M. Berry, R.F. Mercer The Log Analyst, 1977

14. Petrophysical Evaluation of the Bluesky Sand, Bassett Area Alberta J.T. McCoy CIM, 1977

15. Petrophysical Evaluation of the Farewell Structure Sand Reservoir MacKenzie Delta. H.M. Howells, J.R. Wilkinson

16. Offshore East Canada's Organic Type and Color and Hydrocarbon Potential OGJ, 1977

17. Log Interpretation in the High Arctic E.R. Crain CWLS, 1977

18. Some Practical Applications to Improve Formation Evaluation of Sandstones in the MacKenzie Delta. W.L. Johnson, W.A. Linke CWLS, 1977

19. Natural Gas in the Arctic Islands, Discovered Reserves and Future Potential. D.C. Waylett
Canadian Gas Association

20. A Reserves Review of the Pembina Cardium Oil Pool R.A. Purvis, W.G. Bober JPT, 1979

21. The Sidewall Epithermal Neutron Log as a Porosity and Lithology Device in the Zama-Lutose Area of Northwest Alberta J.R. Eade CWLS, 1970

22. Log Interpretation in Complex Gas Bearing Reefs Northeast British Columbia. R.H. Paul SPWLA, 1967

23. Use of the Sidewall Neutron Log in the Keg River Formation of the Zama Area. J.R. Lishman SPWLA, 1967

24. An Empirical Approach to Log Interpretation in the Viking Sand of East Central Alberta. W.C. Cutress SPWLA, 1974

25. A Guide to Improved Formation Evaluation in Carbonates of Northwestern Alberta. A.H. Dorin, A.E. Chase, A. W. Linke 1968-70

26. Petrophysical Evidence of Cementation Differences in the Cardium Sandstone. W.R. Almon CWLS, 1979

27. Road Allowances Drilling Evaluation in the Lloydminster Area R.H. Knudsen, L. Freitag CWLS, 1970

28. Log Interpretation Chart for Western Canada Reservoirs Professional Log Evaluation Ltd. 1978

29. A Log Analysis Manual for the Western Canada Analyst W.D. Smith Lane-Wells, 1978

30. Clinton Exploration and Production on the Ontario Side of Lake Erie. D.Hurd, D. Kingston PE, 1978

31. Canadian Arctic Islands - Cross Section J.S. Sproule and Assoc. 1971

32. Sable Island Geology Heralds Threshold Reserves Oilweek, 1980

33. An Alberta Gas Supply Response Model: Predicting Future Discoveries. C.R. Winter, B.A. Craig Technology, 1981

34. Exploration Prospects and Future Petroleum Potential of the Canadian Arctic Islands. F.G. Rayer JPT, 1981

35. Beaufort Sea: The Biggest Year Ever Frontier Exploration Oilweek, 1981

36. East Coast: The Grand Banks Remain Number One Oilweek, 1981

37. Exploration Potential of the Scotian Shelf R.A. Meneley Drilling Canada, 1981

38. The Successful Application of a Neutron Acoustic Crossplot to the Dolomite Sandstone of the Belloy. W. Calloway, W.D. Smith JCPT, 1982

39. Canada's East Coast: The New Super Petroleum Province E. Mancini, J.W. Payne JCPT, 1982

40. Dome's Dilemma: Long Tools, Thin Sands Energy, 1982

41. Operator Interest Keen in U.S. Beaufort Sea B. Williams OGJ, 1982

42. The Evaluation of Very Shaly Formations in Canada Using a Systematic Approach. H. Kowalchuk, G. Coates SPWLA, 1974

43. Optimizing Completions in the Milk River Sand H.J. Kowalchuk, F.C. Coles CIM, 1974

44. Milk River Saraband Quality Control SOC, 1976

45. Shallow Gas: Ho to Locate Easily Missed Pay Sands G.E. Dawson-Grove World Oil, 1977

46. Shallow Gas: Examples & Interpretations SOC, 1976

47. How Well Logs Were Used to Improve Evaluation of a Gas Storage Project. J.M. Hawkins, R.W. Snyder, S.B. Pahawa JPT, 1977

48. A Modified Shaly Sand Equation for the Western Canada Cretaceous W.D.M. Smith, R.J. Bodileau CWLS, 1977

49. Computer Reconciliation of Sonic Log And Core Analysis in the Boundary Lake Field. F.S. Jeffries, E.M. Kemp Oil In Canada, 1963

50. Countess Oil Field, South Central Alberta: Case History in Finding a Stratigraphic Trap. A.W. McCoy, C.A. Moritz OGJ, 1982

51. HIBERNIA - A Petrophysical and Geological Review R. Benteau, M.G. Sheppard JCPT, 1982

52. Naturally Occurring Gas Hydrates in the MacKenzie Delta C. Bily, J.W.L. Dick Imperial Oil

53. Large Scale Log Interpretation of Water Saturation for Two Complex Devonian Reef Reservoirs in Western Canada. C.R. Glenville SPWLA, 1965

54. Rock Fluid Relationship Studies on the Windfall D-3A Reservoir and Their Application in Evaluating Gas Cycling Effectiveness T.B. McFadzean JCPT, 1977

55. A Simple Method of Verifying the Air/Mercury to Water/Oil Conversion Factor. J. R. Eade CWLS, 1971

56. An Improved Method for the Analysis of Reservoir Rocks Containing Clays. R.E. Jenkins, D.C. Bush, W.R. Aufricht CWLS, 1970

57. Water Saturation Determination in the Keg River Formation of the Zama Field Using Logs and Oil Base Cores. H.N. Collins CWLS, 1970

58. Log Interpretation in the Ricinus Area of West Central Alberta R.H. Paul CWLS, 1970

59. Petrophysical Relationships From the Western Canada Area W.D.M. Smith SPWLA, 1969

60. Formation Water Saturation in Gas Reservoirs - A Comparison of Log Derived Values With Data Derived From Extracted Oil Base Core R.H. Paul SPWLA, 1968

61. The Relationship of Reservoir Permeability to Measured Laboratory Permeability. W.R. Aufricht CWLS, 1968

62. Application of Porosity - Water Saturation Relationships to Log Analysis in Southeast Saskatchewan. A. Heslop CWLS, 1966

ABOUT THE AUTHOR

E. R. (Ross) Crain, P.Eng. is a Consulting Petrophysicist and a Professional Engineer with over 35 years of experience in reservoir description, petrophysical analysis, and management. He has been a specialist in the integration of well log analysis and petrophysics with geophysical, geological, engineering, and simulation phases of oil and gas exploration and exploitation, with widespread Canadian and Overseas experience.

His textbook, "Crain's Petrophysical Handbook on CD-ROM" is widely used as a reference to practical log analysis. Mr. Crain is an Honourary Member and Past President of the Canadian Well Logging Society (CWLS), a Member of Society of Petrophysicists and Well Log Analysts (SPWLA), and a Registered Professional Engineer with Alberta Professional Engineers, Geologists and Geophysicists (APEGGA)