Coast Geological Society

Ventura, California

The Coast Geological Society would like to invite you to the second meeting of the 2017-2018 season!

The second meeting will be on Tuesday, October 17th 2017

Thomas L. Davis, Ph.D. will present his talk titled:

Fault displacement hazards at Aliso Canyon and Honor Rancho natural gas storage fields, southern California

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CGS would like to thank Mike Leary, President and Principal Geologist at Alpine Geotechnical, for sponsoring the October 2017 meeting!

A message from Mike:

Alpine Geotechnical is proud to co-sponsor this month’s Coast Geologic Society meeting.  We are located in Ventura.  Alpine Geotechnical provides engineering geology and soils engineering for a variety of projects, from the initial preliminary investigation to grading and construction monitoring.  We also provide percolation testing for septic design and storm water BMP’s.  Our projects include residential, commercial and agricultural properties.  Call us today!


October 17th 2017 Talk:


Fault displacement hazards at Aliso Canyon and Honor Rancho natural gas storage fields, southern California

 

Abstract: 

 

Faults that have a significant potential for future displacement (IAEA’s and USNRC’s capable fault1,2) and intersect natural gas storage wells in the subsurface are an underappreciated hazard to well integrity. The American Petroleum Institute RP 1171 (API, 20153), that is guiding State of California and Federal new rule-making for gas storage fields, states "Depleted hydrocarbon reservoirs are candidates for natural gas storage because the reservoir integrity has been demonstrated over geologic time by hydrocarbon containment at initial pressure conditions." True, but gas wells at storage reservoirs have not existed over geologic time and when wells cross capable faults there exists a fault displacement hazard to well integrity. If displacement were to occur, then potential exists for methane leakage to the surface and risks to public safety, the environment, energy supply, and a valuable resource. In the US, underground natural gas storage fields supply nearly one-third of our nation’s energy needs and that number is expected to grow in response to ample domestic supplies, and low-carbon fuel demands from new requirements for power generation driven by climate change concerns. As with all energy sources, natural gas comes with its own set of challenges: the largest methane leak in US history occurred at the Aliso Canyon Gas Storage Field (ACGSF). Taking almost four months to control, the ACGSF leak demonstrated the difficulty of stopping an underground leak from one well in a pressured gas storage field, and showed the need to evaluate all hazards to gas well integrity and to estimate and mitigate the risks. At the ACGSF and Honor Rancho fields, all of the storage wells cross the Santa Susana (SSF) and Honor Rancho faults, respectively, to reach their storage reservoirs. Both faults have had significant displacement during the last 2-3 ma, and the SSF may have a slip-rate as high as 7.0-9.8 mm/yr during the last ~700 ka. The Southern California Earthquake Data Center (Caltech) estimates the characteristic earthquake magnitude for the SSF to be from MW 6.6-7.3, and historic records for this range of magnitudes indicate that from 0.3 to 2.8 meters of fault displacement can be expected on the SSF. Earthquake fault movements of up to 0.25 meters severely damaged numerous oil wells in the subsurface at the Wilmington oil field in response to oil field subsidence. These subsidence earthquakes were significantly smaller than the moderate to large tectonic earthquakes common to southern California that will generate much larger fault displacements. To insure public safety and awareness, new Federal and State regulations should require independent and transparent evaluations of the hazard and risk of capable faults for planned and existing gas storage fields.


1, International Atomic Energy Agency: Capable fault has a significant potential for displacement at or near the ground surface (https://www.nrc.gov/reading-rm/doc-collections/cfr/part100/part100-appa.html).
2, United States Nuclear Regulatory Agency: (g) A capable fault is a fault which has exhibited one or more of the following characteristics: (1) Movement at or near the ground surface at least once within the past 35,000 years or movement of a recurring nature within the past 500,000 years. (2) Macro-seismicity instrumentally determined with records of sufficient precision to demonstrate a direct relationship with the fault. (3) A structural relationship to a capable fault according to characteristics (1) or (2) of this paragraph such that movement on one could be reasonably expected to be accompanied by movement on the other (http://www-pub.iaea.org/MTCD/publications/PDF/Pub1448_web.pdf).
3, API, 2015: American Petroleum Institute, Functional Integrity of Natural Gas Storage in Depleted Hydrocarbon Reservoirs and Aquifer Reservoirs, API Recommended Practice 1171, First Edition, September, 2015.


Thomas L. Davis, Ph.D.

Davis (center) and associates field mapping in the Sulaiman Range fold and thrust belt, Baluchistan, Pakistan.

Speaker's BIO:


Thomas L. Davis is a California State Professional Geologist (#4171), owner of Thomas L. Davis Geologist and President of the nonprofit Geologic Maps Foundation, Inc., researcher and author of geologic publications dealing with structural geology, active faulting and earthquakes, oil and gas fields, gas storage fields, and the petroleum potential of central and southern California, Nevada, the Indian subcontinent, and northwestern South America. Davis has a BS and PhD from the University of California. In two papers published in 1988, Jay Namson and Davis showed that the destructive 1983 Coalinga earthquake occurred on a blind-thrust-fault beneath the Coalinga anticline, that the deformed west-side of the San Joaquin basin is an seismically-active convergent wedge, the western Transverse Ranges are an active fold and thrust belt with strain-partitioning along the San Andreas plate boundary, and more generally that subsurface geology needed to be integrated with surface geology to have a more complete understanding of earthquake hazard and risk (Seismically Active Fold and Thrust Belt in the San Joaquin Valley, Central California, GSA Bulletin, v.100, p. 257-273; and Structural Transect of the Western Transverse Ranges, California: Implications for Lithospheric Kinematics and Seismic Risk Evaluation, Geology, v.16, p.675-679). In 1989, Davis, Namson, and Bob Yerkes were the first to show that the deformed margin of the northern Los Angeles basin was underlain by an active, north-dipping blind-thrust-fault system (Elysian Park) and a splay fault of this system caused the destructive 1987 Whittier Narrow earthquake (A Cross Section of The Los Angeles Area; Seismically Active Fold And Thrust Belt, The 1987 Whittier Narrows Earthquake, and Earthquake Hazard, JGR, v. 94, p.9644-9664). Again, their approach emphasized integrating surface and subsurface geology and using interpretative subsurface mapping techniques, software, and data used almost exclusively by the oil and gas industry to fully understand the geology and seismic hazards of an area. Davis and Namson interpreted that the 1994 Northridge earthquake occurred along a deep, south-dipping blind thrust fault (Pico) whose surface expression is the extensive northeast-dip of the northern Santa Susana Mountains, and the Santa Susana fault is possibly a roof thrust to a northward-directed crustal wedge (A Balanced Cross-Section of the 1994 Northridge Earthquake, Southern California; Nature, v. 372, no. 10, p.167-169). Davis continues to emphasize the need to integrate surface and subsurface geologic data to the geologic community. 


Davis’ publications and field guidebook websites:

Tomas L Davis geology click HERE

Geologic Map Foundation click HERE