Abstract

We conducted coring, well logging and formation fluid sampling during the Integrated Ocean Drilling Program (IODP) Expedition 337 "Deep coalbed biosphere off Shimokita" on September 2012 in off-shore Shimokita, Japan. The purpose of this experiment is basic scientific research for deep biosphere and carbon cycle system in the coal bed methane. Wireline logs, cores, cuttings, and mud gas were taken for scientific study. Measurement properties of the well logging were natural gamma-ray, resistivity, density, neutron porosity, sonic velocity, borehole resistivity image, NMR log, pressure, temperature, permeability, and zero-offset VSP. Our strategy for formation fluid sampling was follows:

  1. Geological and lithological interpretation with standard logs,

  2. accuate identification of target layers with borehole resistivity image,

  3. screening of target points with pearmeavility estimation by NMR log,

  4. final screening by permeability with MDT (modular dynamic tester) pretest,

  5. fluid sampling with MDT.

We prepared MDT with Quicksilver probe and in-situ fluid analyzer to take low contamination fluid, special coating single-phase sampling bottles to prevent chemical interaction and to keep in-situ fluid pressure, a more powerful pump module for low permeability, stronger wireline cable to prevent to stack heavy tool stack. We obtained six 250ml full sample bottles from 2456–3646m with water depth 1180m successfully. Our sampling targets were sand layers nearby coal beds. It was very challenging to obtain fluid sampling under the conditions of low permeability formations, open hole, water base mud, and limited operation time. To complete our mission, we used Schlumberger's MDT, quicksilver probe, DURSAN coating shingle phase bottles, and IFA (In-site Fluid Analyzer) to maximize operation efficiency and to minimize contamination. Sampled formation fluid was shared with scientists, and advanced analysis is being carried out in their shore-base laboratories.

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