講演者： Arkadiusz (Arek) Derkowski 先生 日時：12月16日（月）17:30~ 場所：理学部1号館710号室 演題：Free and adsorbed methane in shales 要旨： Mudstones and shales have a complex nm-scale pore structure and a permeability of several orders of magnitude lower than conventional, coarser-grained reservoirs. If rich in organic (carbonaceous) matter (OM), in the course of diagenesis they can become self-sourced unconventional reservoirs of natural gas. Methane (CH4) present in shale formations occurs as two fractions: as free gas occupying pore structure and gas adsorbed on the rock compounds’ surface. The total methane in place content in a shale is limited by the overburden pressure and by the porosity of the rock. Due to their composition dominated by clay minerals, measuring total and effective porosity in shales remains a challenging step in hydrocarbons reserves calculation. Dual-Liquid Porosimetry (DLP) is a new method of measuring total porosity in shales and other ultra-low porosity geomaterials. DLP applies a combination of light kerosene (kerosene immersion porosimetry) and deionized water (water immersion porosimetry) as saturation-immersion fluids. The DLP method returns the maximum porosity fraction available for hydrocarbons and meets the best practice in petrophysics, overcoming the issues posed by conventional porosity measurement techniques. A significant amount of methane can be adsorbed physically on surfaces and in micro- and mesopores. In shales these textural features are commonly controlled by two compounds: organic matter (OM) and clay minerals. In OM-rich shales, the CH4 adsorption is predominantly controlled by OM micropore structure. The mesopore surface area and volume do not play an important role in CH4 sorption. The CH4 loading potential in micropores decreases with increasing thermal maturity of OM; the highest CH4 loading potential is linked to OM before metagenesis (Ro < 2%) where the adsorbed CH4 density equivalent was found greater than the density of liquid CH4. This suggests that in addition to physical adsorption, absorption (dissolution) of CH4 in OM occurs. In OM-poor rocks and sediments, clay minerals contribute to a large portion of the available surface area and microporosity in which methane is adsorbed. Opposite to OM-rich shales, where CH4 adsorption under high pressure corresponds to the sites occupied by CO2, methane adsorption capacity in clay minerals is controlled by N2-accesible micropore volume. CH4 adsorption sites are located mainly outside of the interlayer galleries of expandable clays unless they are open wide enough (e.g. pillared by organic cations or incompletely dried divalent cations). Clays adsorption capacity of CH4 is primarily controlled by the clay particles texture, as the crystallite planar dimensions and the way that they assemble.
講演者：小暮 敏博 教授 日時：10月28日（月）17:30~ 場所：理学部1号館710号室 演題：Visualization of Clays at the Atomic Scale 要旨：粘土鉱物は造岩鉱物の風化生成物として広く地表あるいは海洋底を覆っており，地球表層の物質循環あるいは生命・人間活動に深く関連するキーマテリアルと言うことができる．はたして粘土鉱物とはどのような構造を持ち，どのようにして形成されてきたのか？ この物質には多くの未解明の問題が残されている．粘土鉱物の多くは層状珪酸塩鉱物（phyllosilicates）という非常に異方的な構造をもつ故に，他の鉱物には見られない独特の特徴を示すことになる．そのひとつが多くの粘土鉱物は”3次元周期性を持たない”ということである．この3次元周期性の消失という問題のため，これまで人類が結晶構造の解析に用いてきた回折（Diffraction）的手法だけでは，粘土鉱物の真の構造を解明することはできない．そのため，我々は透過電子顕微鏡による粘土鉱物中の原子配列の直接観察に挑むことになる．しかしそこには電子損傷という大きな壁が立ちはだかっており，決して安易な道ではない．本発表では，演者が大学に籍を置いてから四半世紀の間に進めた電子顕微鏡による粘土鉱物の構造の”可視化”によって，粘土鉱物の構造と成因についてどのようなことがわかったのか，その一部を紹介したい．
