Meeting Information

"Application of NMR for Evaluation of Tight Oil Reservoirs"

Richard E. Lewis
Petrophysics Technical Manager, Unconventional Resources
Schlumberger

The reservoir quality (RQ) of gas shale reservoirs can be equated to the amount of kerogen or Total Organic Carbon (TOC) because the majority of the producible pore volume is hosted in the organic matter (OM pores). Determining the RQ for a tight oil is more difficult due to 1) the presence of two hydrocarbon types at reservoir conditions--high-viscosity, low-maturity bitumen and light oil; plus 2) the presence of pore systems hosted within the inorganic matrix (IP pores).

Comparison of paired core and log NMR measurements from the Eagle Ford and other shales indicates that a portion of the pore fluids that are measured with the log are not present in the core sample. This pore volume has been expelled during core extraction and storage. The remaining pore volume is generally not producible, and this hydrocarbon fraction represents either bitumen or oil sorbed to the OM pore walls. The difference between the two pore volumes has proven to be an acceptable proxy for the determination of producible pore volume, and a primary challenge is to differentiate between the water and hydrocarbon fractions. This is currently performed through core NMR using fluid reinjection.

Jarvie (2012) introduced an index (Oil Saturation Index) to highlight producible zones within a tight oil reservoir. It is based on RockEval analysis, and it is the ratio of producible oil (S1) divided by all hydrocarbons as measured by this technique (S1, S2, and S4). This total includes the carbon in light oil, bitumen, and kerogen. The higher the ratio the higher the RQ. Higher RQ can be caused by 1) conversion of bitumen to light oil, or 2) migration of light oil from OM to IP pores—a hybrid reservoir. We have adapted this index for in-situ log measurements and have adjusted it to award intervals with higher weight % light oil. In contrast to a gas shale, the intervals with a lower kerogen content are generally more prospective. Examples from the Bakken, Eagle Ford, Woodford and several  international shales will be presented.

The exclusive use of a T2 distribution limits ones ability to differentiate between pore hydrocarbon phases, pore type (OM vs. IP), and pore fluid (water vs. oil). The addition of T1 distribution permits one to quantify bitumen (above a lower T1/T2 bound) and differentiate between OM and IP pores up to intermediate T2 relaxations. An enhanced logging service that measures both T1 and T2, and which is also optimized to provided better accuracy at lower T2 relaxations, is currently undergoing field tests.

From the President

Suzanne Heskin

I hope you all had a fantastic summer filled with hiking, biking, camping, or your favorite Colorado activity!  It went quickly for me, and my daughter is already an old pro at being in the first grade!  DWLS Season is upon us, time to focus on sharing knowledge and improving ourselves professionally again.  Hopefully some or many of you were able to attend the SPWLA symposium in CA, or URTeC in TX.  These conferences continue to be vital to the health of the industry, especially in downturns such as this.  I invite any of you who attended to share with those who didn't.  Share ideas, thoughts, papers, CDs, suggestions for speakers as well.

Bob Cluff worked over the summer to line up some high quality speakers for the fall, and I hope attendance remains as high as it was last year, if not higher.  Bring coworkers or friends to our meetings who haven't attended before and perhaps our membership can grow a bit this year.

Moving forward into the 2015-2016 year, please feel free to approach any board member if you have concerns, suggestions, or compliments!

Thanks, welcome back, and I look forward to seeing everyone soon!

From the Vice President - Technology

Bob Cluff (The Discovery Group)

We're off to another exciting year for DWLS.   My plan for 2015/16 will be to combine selected technology/tool talks from the major service providers with interpretation and case history talks on the 5 or 6 major tight reservoir plays.  In these economically challenging times most operators are focused on just a small number of key play opportunities with the best economics, and I'll follow the crowd and try to focus our attention on those key plays.  Nonetheless, new technology is our lifeblood and it's important we stay on top of new developments as they occur.

I have lined up for us two talks this Fall from the 2015 SPWLA conference in Long Beach on NMR applications to tight reservoirs (Rick Lewis in September, and Margaret Lessenger in November), and a third on advanced logging measurements and core data from the Bakken play (Gary Simpson in October).   I'll also be drawing from recent papers presented at URTeC and AAPG to fill out the Spring 2016 program.  If you attended any of these summer conferences and saw something you think is particularly appropriate for the chapter, please contact me right away and let me know – I can't see every paper!

Plans for the DWLS Fall and Spring workshops will be forthcoming shortly.   There might be some changes in the planning.

From a Vice President - Membership

Aaron Fisher (Tracker Resources)

Hello everyone!

Fall is shortly around the corner which means that the yearly renewal process is upon us.  Those of you who have not renewed your yearly dues will be receiving a friendly reminder from me with renewal instructions soon.  If you would like to be proactive, please follow the link: (http://dwls.spwla.org/Membership_Form.php.)  All active members are given a three month grace period to renew their membership.  November marks the end of the grace period.  On a positive note, the low commodity prices have not hampered membership as we are up to 370 active members, of which 307 are lifetime members.

There has been a lot of turnover in the industry in the past six months.  Please be sure to send you updated contact information (VP_Membership@dwls.spwla.org) so we can keep everyone current.  Don't miss out on hearing about the holiday party, spring workshop, and all the monthly talks.

From a Director (Monthly Beverage Sponsorship, and Social Events)

Bryan Page (Weatherford)

The drinks during our monthly lunch meeting are traditionally sponsored by a company or organization. This practice serves several worthy objectives. First, it encourages people to arrive on time, because after 11:30 no free drink coupons are issued, second it creates a good social atmosphere prior to the talk, and third it gives the sponsor the opportunity to promote their organization in the DWLS monthly newsletter and at the monthly meeting. Therefore we encourage our members to sponsor these drinks or contact their marketing department to do the same.

For more information or to save your spot, please contact Bryan Page Bryan.page@weatherford.com

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