印度 Raniganj 煤田煤层割理/裂缝、基质相关孔隙和物理力学特性的有机岩型控制,ACS Omega

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印度 Raniganj 煤田煤层割理/裂缝、基质相关孔隙和物理力学特性的有机岩型控制
ACS Omega ( IF 3.7 ) Pub Date : 2021-07-21 , DOI: 10.1021/acsomega.1c02041
John Buragohain _{1,

2} , Vinod Atmaram Mendhe ₂ , Atul Kumar Varma ₁ , Priyanka Shukla ₂

Affiliation

已经研究了 Barakar 和 Raniganj 组煤层的有机岩型特性，以评估割理的起源、赋存过程及其对强度特性的影响。煤条在煤层气回收、地下矿山地层力学、选矿、粉化等方面有着广泛的应用。然而，关于印度煤的割理发生和控制参数的信息非常有限。在这种情况下，从与 Raniganj 煤田的 Barakar 和 Raniganj 等含煤地层相交的 8 个勘探钻孔中回收了总共 31 个煤样。我们在煤层中确定了四种不同的岩型：(i) B，亮煤；(ii) Db，暗带状煤；(iii) Bb，亮带状煤；(iv) Bd，带状煤。丰富的亮带相关岩型表明有机质在沉积后达到早期缺氧条件。Barakar煤的割理系统在岩石类型、有机质类型、热成熟度和凝胶化程度的控制下优于Raniganj煤。煤中的碳富集过程主要控制着巨大的割理成因模式。由宏观、微观和扫描电子显微镜 (SEM) 研究确定的割理强度随煤层深度呈正趋势，假设宏观到纳米割理在脱挥过程中由于塑性损失而相互依赖和发展。由于表观遗传特征，场发射扫描电子显微镜（FE-SEM）照片显示出复杂的微裂缝和孔隙结构。镜质带表明它包含部分变形的平面割理系统。归因于煤脆性的石英风化特性也有助于割理的形成。总粘土含量与不同割理强度呈反比关系，表明含水粘土由于其固有的超细特性而膨胀，因此不支持割理构造。然而，当有机-无机物质达到干热条件时，它会抑制不规则裂纹的发展。研究煤中与不同孔隙结构相关的微裂缝可分为七种类型：(i) 玻璃体相关的规则开缝孔隙，(ii) 玻璃质炭相关的不规则孔隙，(iii) 部分填充粘土的不规则裂缝孔隙, (iv) 沿粘土层理面的裂变孔，(v) 由于从侵入体接收的外部热量而形成的有机孔隙，(vi) 在压实和热转变过程中形成的深有机孔隙，以及 (vii) 被沼泽藻类阻塞的孔隙裂缝。粘土含量与物理力学性质呈正相关，表明粘土保持裂缝和孔隙的胶结特性。Barakar 和 Marren 测量煤的强度特性受热成熟度、岩型特征和有机-无机含量的影响存在显着差异。表示粘土保持裂缝和孔隙的胶结特性。Barakar 和 Marren 测量煤的强度特性受热成熟度、岩型特征和有机-无机含量的影响存在显着差异。表示粘土保持裂缝和孔隙的胶结特性。Barakar 和 Marren 测量煤的强度特性受热成熟度、岩型特征和有机-无机含量的影响存在显着差异。

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Organo-Lithotype Controls on Cleat/Fractures, Matrix-Associated Pores, and Physicomechanical Properties of Coal Seams of Raniganj Coalfield, India

The organo-lithotype properties of Barakar and Raniganj Formation coal seams have been investigated to assess the process of cleat origin, occurrence, and their influence on strength properties. Coal cleats have wide applications in coalbed methane gas recovery, underground mine strata mechanics, beneficiation, and pulverization. However, there is very limited information available on the cleat occurrence and controlling parameters of Indian coals. In this view, a total of 31 coal samples were retrieved from eight exploratory boreholes intersecting coal-bearing formations like Barakar and Raniganj in the Raniganj Coalfield. We identified four distinct lithotypes in coal seams: (i) B, bright coal; (ii) Db, dull banded coal; (iii) Bb, bright banded coal; and (iv) Bd, banded coal. The abundance of bright-band-associated lithotype indicates organic matter that attained the early anoxic conditions after deposition. The cleat system in Barakar coal is comparatively better than in Raniganj coal controlled by the lithotype, type of organic matter, thermal maturity, and gelification extent. The carbon enrichment process in coal mainly controls the megascopic cleat genesis pattern. The positive trend of cleat intensities with the depth of coal seams as determined by megascopic, microscopic, and scanning electron microscope (SEM) studies postulates that the macro- to nanocleats are interdependent and developed during devolatilization due to loss of plasticity. The field emission scanning electron microscopy (FE-SEM) photographs have shown intricate microfractures and pore structures owing to the epigenetic characteristics. Vitrinite bands indicate that it comprises the partially deformed planer cleat system. The resistance to quartz weathering nature attributed to coal brittleness properties also contributed to cleat genesis. The total clay content exhibits an inverse relationship with different cleat intensities, suggesting that hydrous clay swells due to its inherent ultrafine characteristics, thus not supporting the cleat construction. However, it ropes the development of the irregular crack when organo–inorganic matter achieves the dry thermal conditions. The microfractures linked with different pore structures in studied coals can be classified into seven types: (i) vitrite-associated regular open-slit pores, (ii) vitriinertite-char allied irregular pores, (iii) irregular fracture-pore partially filled with clay, (iv) fissile pores along bedding planes of clay, (v) organic pores evolved due to external heat received from intrusives, (vi) deep organic pores evolved during compaction and thermal transformation, and (vii) pore fractures blocked by boghead algae. The clay content showed a positive relationship with physicomechanical properties, signifying the cementing characteristics of clay holding fractures and pores. There is significant variation in the strength properties of Barakar and Marren measures coal influenced by thermal maturity, lithotype characteristics, and organo–inorganic content.

更新日期：2021-08-10

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