Kinetics of the opal-A to opal-CT phase transition in low- and high-TOC siliceous shale source rocks Danica Dralus Stanford University, now at BP Mike Lewan USGS, Denver, CO (retired) Ken Peters Schlumberger, Stanford University BPSM Annual Meeting November 12, 2014 Stanford, California
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Kinetics of the opal-A to opal-CT phase transition in low ... · Siliceous deposits undergo phase transitions. 3 Opal-A is amorphous and easy to dissolve. Opal-CT is microcrystalline.
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Kinetics of the opal-A to opal-CT phase transition in low- and high-TOC siliceous
shale source rocks
Danica Dralus Stanford University, now at BP
Mike Lewan USGS, Denver, CO (retired)
Ken Peters Schlumberger, Stanford University
BPSM Annual Meeting November 12, 2014 Stanford, California
Outline
• Introduce opal-CT/quartz transition in the oil patch
• Recap opal-CT to quartz experiments*
• Describe new opal-A to opal-CT experiments
• Report preliminary opal-A to opal-CT kinetics data
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*For additional details, see my dissertation (Stanford, Aug 2013): Chemical interactions between silicates and their pore fluids: How they affect rock physics properties from atomic to reservoir scales
BPSM affiliates meeting, Nov 12, 2014
Siliceous deposits undergo phase transitions.
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Opal-A is amorphous and easy to dissolve. Opal-CT is microcrystalline. Quartz is fully crystalline and hard to dissolve. They are all just SiO2 in different arrangements!
grad student work
post-doc work
BPSM affiliates meeting, Nov 12, 2014
Rock properties change with the phase transition, sometimes resulting in diagenetic traps.
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This is a known trapping feature in the San Joaquin Basin.
• mineral density increases • porosity increases • permeability increases • brittleness increases for
quartz
BPSM affiliates meeting, Nov 12, 2014
Finding diagenetic traps with seismic data is tricky.