Meeting Information

"Sonic velocity and other petrophysical properties of source rocks of Cody, Mowry, Shell Creek, and Thermopolis Shales, Bighorn Basin, Wyoming"

Phil Nelson
U.S. Geological Survey

The petrophysical properties of four shales are documented from well log responses in 23 wells in the Bighorn Basin in Wyoming.  Depths of the shales examined range from 4,771 to 20,594 ft.  The four shales are the Thermopolis (T) Shale, the Shell Creek (SC) Shale, the Mowry (M) Shale, and the lower part of the Cody (C) Shale, all of Cretaceous age.  These four shales lie within a 4,000-ft, moderately overpressured, gas-rich vertical interval in which the sonic velocity of most rocks is less than that of an interpolated trendline that reflects a normal increase of velocity with depth.  Sonic velocity, resistivity, neutron, caliper, and gamma-ray values were determined from well logs at discrete levels in each of the four shales in 23 wells.

Sonic velocity in all four shales increases with depth to a present-day depth of about 10,000 ft; below this depth sonic velocity remains relatively unchanged.  Velocity (V), resistivity (R), neutron porosity (N), and hole diameter (D) from caliper logs in the four shales vary, such that V_M > V_C > V_SC > V_T,  R_M > R_C > R_SC > R_T,  N_T > N_SC ~ N_C > N_M, and D_T > D_C ~ D_SC > D_M.  These orderings can be partially understood on the basis of rock descriptions.  The Mowry Shale is highly siliceous and by inference comparatively low in clay content, resulting in high sonic velocity, high resistivity, low neutron porosity, and minimal borehole enlargement.  The Thermopolis Shale, by contrast, is a black fissile shale with very little silt; high clay content causes low velocity, low resistivity, high neutron response, and results in the greatest borehole enlargement.  The properties of the Shell Creek and lower Cody Shales are intermediate to the Mowry and Thermopolis Shales.

From the President

Stefani Whittaker (The Discovery Group)

Where did our Society come from?

Our society was formed in 1956 as a study group with the principal purpose, according to the old bylaws, of learning about “formation evaluation with particular emphasis on all types of well logging techniques.” In June of 1964 the executive committee and membership voted on and approved the motion to become an affiliate of the Society of Petrophysicists and Well Log Analysts. However, joining SPWLA meant altering the original bylaws, and required members to be active professionals with at least 9 years of experience in a petroleum based field and increased dues to $2.00 per year for all members.

Over the years our society has grown to over 300 members and we are currently the largest chapter of SPWLA in the world. We boast a very talented and dedicated group of individuals who have made this chapter a success story. The topics of our meetings and short courses have drawn in people from around the United States and the world. We have an outstanding reputation in SPWLA, and I for one am proud to be a part of this great organization.

We have been extended an invitation to host the 2011 SPWLA convention in Colorado. This is a great opportunity for us to share with our parent organization our talents and our great state. A steering committee has been formed and will be looking for event chairs in the near future. If you would like to volunteer, please contact either Dominic Holmes  (Dominic.Holmes@DigitalFormation.com) or Sue Cluff (suecluff@discovery-group.com) for more information. Thanks so much for being a member of this great organization and for your continuing support!

From the Vice President - Technology

Terri Olson (EOG Resources)

DWLS 2009 Fall Technology Workshop on Capillary Pressure

The fall workshop was a popular event, with a capacity crowd of over 110 at the student center at Colorado School of Mines on Oct. 19. Attendance was boosted by more than the usual number of students, mostly graduate students of two of the speakers, professors Ramona Graves of CSM and Norman Morrow of the University of Wyoming. Dr. Graves got everyone’s attention with her statement that “Rocks are like women; they remember what you do to them forever,” in her opening presentation on cap pressure fundamentals. Pat Lasswell of Weatherford Labs explained the process and rationale for vapor desorption cap pressure measurements, and showed data from tight gas sands with very low Sw’s and some shales.

Bob Barree gave an impressive talk on water block, noting that capillary pressure is only one of the causes of this type of formation damage. Dr. Morrow followed with a discussion of capillary pressure and surface energy, relating surface area to the work involved in fluid displacement. The finale was presented by Steve Bailey of EOG Resources, who polled the audience at the beginning of his talk on closure and compressibility corrections to capillary pressure data in shales and found that about 2/3 of them work on shale reservoirs on a daily basis. 

Some of the comments we received:

"Overall, the content and topics were useful.  Dr. Barree’s presentation was very applicable and useful."

"It helped to hear about negative capillarity in limestone and issues and solutions about it.  It was a great experience!"

"Everything covered was of interest and useful to me."

"Nice piece of original work by Steve Bailey."

"Very good workshop - and at a good price.  Thanks for organizing this."

From the Vice President - Membership

Dan Krygowski (The Discovery Group)

DANGER!! WILL ROBINSON... and the rest of the DWLS membership as well. The deadline for annual dues is approaching, and while people have been great at using PayPal for luncheon costs, very few have used PayPal (or checks, or greenbacks) to become current with dues.

So, here’s what you do... Go directly to http://dwls.spwla.org/Luncheon_Reservation.htm (do not pass GO, do not collect $200) and under the Membership Dues title, select the Duration (One-year or Lifetime) and press the Add to Cart button. Take out your credit card and follow the instructions to once again become one with the petrophysical force.

Your mission, should you decide to take it, is to overwhelm Noga and Dan with dues notices, and see if we will self-destruct in the process. If nothing else, your response may stop these mixed references in my next message.

From the Secretary / Treasurer

Scott Brooks (Forest Oil Corporation)

Below is the statement of accounts for the DWLS, as of October 28^th, 2009.

Notable Events:

• $20,000 Donation for the SPWLA Scholarship Fund
• $500 Hole Sponsorship for the DGS Golf Tournament

From the Past President

Bill Rodgers (Weatherford International)

The DECEMBER MEETING is our HOLIDAY SOCIAL!

The 2008 Holiday social was well attended and there were many comments from the attendees that they enjoyed the event. I know I certainly did. Therefore, we're doing it again.

The final venue has not been chosen but, the format has; just $10 per person charge, and there will be drawings for some fine prizes. Some of the prizes will be of use to your spouse/friend that is not in the industry (e.g. not just rocks). The event is basically a "happy hour" with appetizers. The cover charge includes 2 drink tickets per person. All of this for 50% of our normal luncheon price.

While the location isn’t final, it will be on the afternoon of the 3^rd Tuesday of December (December 15, 2009). So mark your calendars.

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