Direct pressure measurement in ocean drilling: a new pressure penetrometer

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Direct pressure measurement in ocean drilling a
new pressure penetrometer
Hui Long
Geo-Environmental Engineering Program
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CORKs ACORKs
Penetration Test
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After Trehu 2003
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Recorded pressure dissipation
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Modeled pressure dissipation
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Hypotheses

• A probe with two diameters, two pressure ports
  and a particular length may have a crossover
  point on the dissipated pressure vs. time curve
  recorded at the two pressure ports
• The pressure port on the thin diameter probe may
  capture a bench feature

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Proposed Research

• Improvements of theoretical model
• Theoretical analysis preliminary design of the
  dual pressure port tapered probe
• Experimental tests

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Strain Rate
Source/sink solution
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Conformal Mapping
After Milne-Thomson 1950
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Surface Friction
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Soil Model
Advantages MIT-E3 vs. MIT-T1 Describe normally
to lightly overconsolidated soils with only one
set of parameters effective stress model, allows
coupled consolidation analysis, enables direct
permeability measurement
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Theoretical Analysis

• Pressure response vs. Probe geometry
• The far field pressure dissipation behavior
• Installation pressure along probe
• Dual pressure port tapered probe Formation of
  crossover point and bench
• Soil properties

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Engineering Design

• Buckling analysis
• Borehole pressure
• Borehole temperature
• Driving/pullout force

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Chamber Test
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Field Test

• Crossover point and bench formation vs. probe
  geometry port positions in natural sediments,
  and the pressure/permeability estimation
  technique
• Integrity of engineering performance hydraulic
  connections, electric connections, data
  acquisition, etc

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Final products

• Multiple probe geometries for different sediments
  and a cookbook approach to select the appropriate
  geometry for deployment
• Simple software to quickly interpret in-situ
  pressure and permeability

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?
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If one combines parallel flow with a number of
sources and sinks, it can be shown that the
resultant flow contains one set of streamlines
forming a closed surface. Fluids flows around
this streamline surface as if it were a solid
body.
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• Borehole application
• Fast penetration rate
• Saturated Low perm sediments

Undrained
Strain Path Method
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Outline

• Why pore pressure and permeability are important
  and how to measure them?
• 2. Application of currently available
  penetrometers DVTP-P piezoprobe
• 3. Hypothesis A dual pressure port tapered probe
• 4. Proposed research

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What is in-situ pressure?
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Hydrologic properties
EstimateC1.051.4x10-6 m2/sk2.43.8x10-16 m2

Lab TestCv2.5x10-7 m2/sk1.4x10-16 m2
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Penetration test
p
t
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Transducer Diaphragm
Tube
Filter stone
Future work
1. Field test in early December
1. System compressibility
2. Surface friction
3. New soil model rate-dependent
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Acknowledgements

• Profs. Flemings Derek Elsworth (PSU) Dr.
  Germaine Prof. Whittle (MIT)
• Xiaoli Liu Matthew Chartier
• 3. NSF GeoFluids consortium

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