Effect of organic material on mechanical, hydrological, and microstructural properties of mudstones

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Author(s): Altobelli, Melissa Ashlyn; Reece, Julia S.
Author Affiliation(s): Primary:
Texas A&M University College Station, College Station, TX, United States
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: In this research we analyze the influence of organic material on the mechanical and flow properties of mudstones. We uniformly mix peat, milled and harvested by Bord na Mona from the surface of bogs in Ireland, with natural mudstone from Site C0011 in the Nankai Trough, offshore Japan, obtained during Integrated Ocean Drilling Program Expedition 322. The mudstone had previously been disaggregated into a homogeneous dry powder of clay- and silt-sized particles. The peat is ground and dry-sieved to achieve a similar particle size distribution as the mudstone (<63 micrometers). In order to understand the mechanical and hydrological processes affected by peat, we prepare dry peat-mudstone mixtures with three different peat concentrations: 0 wt%, 5 wt%, and 10 wt%. Then, these peat-mudstone mixtures are saturated with deionized water at a water content of 109%, formed into stable slurries, and uniaxially compressed to an axial stress of 100 kPa using resedimentation, a method that simulates the natural behavior of deposition and burial in the laboratory under controlled conditions. How the organic material interacts with the mudstone matrix and pore fluid under compression influences the physical properties of the mudstones such as porosity, compressibility, and permeability; all of which are measured in the resedimentation experiments. We will also analyze the microstructural changes as a function of peat concentration using a petrographic microscope and scanning electron microscope. Due to the fibrous and absorbent nature of peat, we anticipate the peat to force tightly packed clay particles in the mudstone apart resulting in a looser microstructure and increased porosity, and thus, a higher compressibility and permeability. Understanding the controls on the mechanical and flow properties of hydrocarbon-bearing, fine-grained formations is crucial for exploration and successful production from hydrocarbon reservoirs. Additionally, this study has large implications for soil water storage and soil amendment to improve plant growth and health in clayey soils.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Clastic rocks; Expedition 322; IODP Site C0011; Integrated Ocean Drilling Program; Mudstone; NanTroSEIZE; North Pacific; Northwest Pacific; Pacific Ocean; Sedimentary rocks; Shikoku Basin; Uniaxial tests; West Pacific
Coordinates: N324944 N324945 E1365256 E1365254
N324400 N325000 E1365600 E1365200
Record ID: 2017087211
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