Abstract
Pulsed-neutron logs are a staple of time-lapse monitoring programs for saline aquifer carbon capture & sequestration (CCS) projects and are unsurprisingly the most frequently run wireline logs in both injection and monitoring wells. While the emphasis imposed by government regulators and the focus of operators to date has been on verification of CO2 containment, it is envisioned that a savvy interpretation of the multiple independent measurements should be able to unlock much greater value for the project than merely detecting the location of stored CO2. Recently introduced capabilities for novel measurements and improved environmental compensation should further increase the repeatability, interpretability, and value of these logs.
We reviewed more than 30 time-lapse runs of pulsed-neutron logs acquired over a period of 15 years on three mature CCS projects using both previous- and new-generation pulsed-neutron tools, including measurements of formation sigma, hydrogen index, and fast neutron cross section. Special attention in processing is required when changes occur to the wellbore environment between runs, although this is mitigated by the improved environmental compensation scheme of the newer tool. We performed both standalone estimates of CO2 saturation from single-physics time-lapse measurements and simultaneous interpretation of multiple independent time-lapse measurements and studied the results side-by-side with open hole log interpretation, core analysis and well test results from the evaluation phase. The apparent changes in saturation were framed within the context of the injection history and important events in the life of the wells.
A first finding is that differences in apparent CO2 saturation between the various independent measurement physics of the pulsed-neutron tool are often reconcilable and may carry additional information about the state of the well or reservoir. With respect to verification of containment, depending on well configuration, it may be possible to differentiate between CO2 in the formation and CO2 in the annulus. The interpreted CO2 saturation itself can have different significance depending on the timing of acquisition and the type of well. Measured at the right time, it is a direct in situ measurement of formation CO2 storage efficiency. In other cases, the interpretation reveals formation dry-out in the near wellbore region of injection wells, a condition that may presage loss of injectivity. We now understand that it is important for operators to plan the timing and frequency of pulsed-neutron runs according to what they want to measure and not based solely on regulatory obligations.
In a CCS project, time-lapse pulsed-neutron logs should be thought of as much more than simple indicators of the presence and migration of CO2. They give important information about migration pathways. They can also help to quantify essential uncertainties on reservoir performance that are difficult to ascertain during evaluation. For example, storage efficiency is difficult to quantify with open hole logs, since the formation is initially at zero CO2 saturation. Yet it is one of the keys to determining the ultimate storage capacity of any reservoir. Time-lapse pulsed-neutron logs provide an abundance of information that, when properly history matched, can greatly improve our models of CCS reservoirs to better navigate both the economic and operational risks associated with these projects.
Speaker Biography
Robert Laronga joined SLB as a wireline engineer in the Permian Basin in 1994 upon receiving a B.A. in Geology from Cornell University. He held various US and international positions in operations, sales, product development and product marketing, as well as petrotechnical roles as a Geologist, Petrophysicist, and Integrated Technical Team Lead. Rob is CCUS Subsurface Measurements Lead for operations in onshore North America and has contributed to more than 30 CCS and CCUS projects during the past four years.
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Regular luncheon reservation: 
Vegetarian luncheon reservation:
Use one of the PayPal links above to make your luncheon reservation.
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Forward this newsletter to a friend to invite them to the luncheon.
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When
Tuesday, November 14, 2023
11:20 am - 1:30 pm
Where
Wynkoop Brewing Company
(tell me how to get there)
Cost
$30 per person
$35 at the door (space permitting)
January's Talk
Adapting Music Recognition Technology for Tops Picking and Quality Control
Alan Lindsay
Vesmir
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From the President
Tamara Maxwell
It’s been an active couple of weeks in the oil and gas industry with acquisitions being announced by a couple of the supermajors showing their willingness to continue to invest in the industry! Our talk this month will be focusing on another area of the industry, which is a hot topic, CCS evaluation.
We will be holding the talk at Wynkoop again this month on Nov 14.
I hope to see many of you there and as always please feel free to reach out to the board with any questions or ideas!
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From the VP - Technology
Ridvan Akkurt
We are happy to announce that our January speaker will be Alan Lindsay of Vesmir, Denver. The title of his talk: ‘Adapting Music Recognition Technology for Tops Picking and Quality Control’. A very innovative and equally interesting piece of work.
For our Spring Workshop, we are considering two themes.
- One would be Machine Learning / AI, with a scope beyond just petrophysics.
- The other is New Energy, a wide variety of subjects, including CCUS, geothermal, wind, Lithium, hydrates, emission monitoring, etc.
Please share your thoughts with us, we are open to suggestions for themes and speakers.
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Calendar of Events
Click the calendar to the right to view events on the web.
Other Important Events
2024 SPWLA Annual Symposium, May 19-22, 2024 (Rio de Janeiro, Brazil)
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DWLS Sponsors
Click here to view the sponsors on the website, or click on any image to contact a sponsor.
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Chapter Statistics
Statistic
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This Year
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3-Year Average
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| # of Active members * |
270 |
296 |
| # that are New members |
3 |
2 |
| # that are Students * |
10 |
7 |
| # that are Lifetime Members * |
247 |
258 |
| September luncheon meeting attendance |
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40 |
| October luncheon meeting attendance |
10 |
33 |
| November luncheon meeting attendance |
|
45 |
| Holiday party attendance |
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26 |
| January luncheon meeting attendance |
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47 |
| February luncheon meeting attendance |
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38 |
| March luncheon meeting attendance |
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26** |
| April luncheon meeting attendance |
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36** |
| May luncheon meeting attendance |
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36 |
* Note that we did a thorough cleanup of bad email addresses that resulted in some of our members being removed until they can be tracked down again. So this year's membership numbers are going to be a bit lower.
** These numbers are skewed due to COVID-19 luncheon cancellations.
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The DWLS Newsletter is published monthly September through June by the Denver Well Logging Society. For information on membership or advertising, contact the editor. For other inquiries, contact a member of the Board of Directors.
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