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The U.S. Geological Survey Gas Hydrates Project

Laboratory and Field Support

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USGS personnel leak-testing the IPTC.

The Instrumented Pressure Testing Chamber (IPTC)

A device for measuring the physical properties of naturally-occurring, hydrate-bearing sediment at nearly in situ pressure conditions.

Motivation

Methane hydrate must remain at or near the moderate pressure and low temperature “in situ” conditions that it experiences in nature in order to remain stable. As shown in this movie, methane hydrate exposed to ambient conditions will destabilize and vanish, significantly altering the texture, strength, and other properties of the sediments. Avoiding this problem requires a system like the Instrumented Pressure Testing Chamber (IPTC), which maintains the in situ hydrostatic pressure of a recovered pressure core so that the properties of a hydrate-bearing sediment core can be measured. The IPTC was designed and built at Georgia Tech by J.C. Santamarina starting in 2004 and is used by the USGS Gas Hydrates Project to test pressure cores recovered during field programs.

Capabilities

The IPTC is the first instrument capable of directly measuring the seismic wave velocity, strength, and electrical properties of hydrate-bearing sediment recovered in pressure cores and held at nearly in situ hydrostatic pressure through their entire recovery and analysis period. Hydrate-bearing sediment in the IPTC can also be depressurized in a controlled fashion to provide physical property information during production-style testing. Although the IPTC has a standalone fluid pressurization system, the IPTC requires an external core positioning system, such as the Core Manipulator developed by Georgia Tech, or the Geotek Pressure Core Analysis and Transfer System (PCATS). The IPTC also relies on third-party cutting tools to shorten pressure cores that are too long to be accommodated in its chamber.

Specifications

The standard specifications for the IPTC are given below. A chamber with a different diameter or length can be built to accommodate measurements on pressure cores or pressure core sections from different pressure coring systems.

  • Length of IPTC: 700 mm (27.6 inches)
  • Diameter of IPTC: 65 mm (2.56 inches)
  • Diameter of drill rods: 7.9 mm (5/16 inch)
  • Maximum tested pressure: 34.5 MPa (5000 psi)
  • Typical working pressure: 10.3 – 20.7 MPa (1500 – 3000 psi)
  • Field Operations

    The instrument was deployed for the first time to analyze pressure cores recovered during the Leg 1 of the DOE/Chevron JIP coring in the deepwater Gulf of Mexico in 2005. It was subsequently used by Georgia Tech to analyze cores from the Indian National Gas Hydrates Program (NGHP1) and from the Korean Ulleung Basin Gas Hydrates Program (UBGH1). In January 2013, the IPTC was used in Sapporo, Japan to analyze pressure cores obtained from the Nankai Trough by the Japanese Methane Hydrate 21st Century (MH21) Project.

    image of IPTC body
    A pressurized, stable, hydrate-bearing sediment core can be fed through the IPTC body, shown here being used in Singapore to support the Indian National Gas Hydrates Program (NGHP1).
    image of probe for iptc
    When assembled, the probe passes through the threaded rod, ball valve and into the IPTC, with an o-ring to prevent fluid leaking back along the probe length. 
    image of iptc measurement sensors
    IPTC measurement sensors. Small-strain mechanical properties are quantified with compressional (Vp) and shear (Vs) wave-velocity measurements across the core diameter in the IPTC.
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    This page last modified on Friday, 26-Apr-2013 13:24:36 EDT