--> Abstract: Petroleum Generation and Primary Migration in Coal Related to Coal Composition: Evidence from Petrography and Pyrolysis, by P. K. Mukhopadhyay, P. G. Hatcher, and J. H. Calder; #91012 (1992).

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ABSTRACT: Petroleum Generation and Primary Migration in Coal Related to Coal Composition: Evidence from Petrography and Pyrolysis

MUKHOPADHYAY, P. K., Global Geoenergy Res. Ltd., Halifax, Nova Scotia, Canada, P. G. HATCHER, Penn State University, University Park, PA, and J. H. CALDER, N. S. Dept. Natural Resources, Halifax, NS, Canada

Selected samples of coal (Ro: 0.25 to 1.25%) from various deltaic and intermontane basins of the world (Paleocene-Eocene of Texas, Carboniferous of Nova Scotia, Eocene-Miocene of Mahakam Delta, Indonesia, etc.) were analyzed by fluorescence microscopy, Rock-Eval pyrolysis, nuclear magnetic resonance, and anhydrous and hydrous pyrolysis to evaluate the liquid and gaseous hydrocarbon generation and primary migration criteria. Liquid hydrocarbon potential in coal is related to hydrogen content of the maceral associations (coal composition) which are, in turn, closely connected to vegetation pattern and Eh/pH condition of paleopeat-mire. According to hydrogen content, coal is classified into five compositional types: algal (boghead), Type I; sapropelitic (exinitic), Type IIA; mixinitic (m xed), Type IIB; humic (vitrinitic), Type III; inertinitic, Type IV. Each of these compositional coal types have characteristic hydrocarbon products generated during pyrolysis; each of them can be related to distinctive maceral composition. Both mixinitic and sapropelitic coals are typical oil-source rocks that generate > 250 mg/g TOC (>10% hydrocarbons on dmmf basis); humic coal (HC <225 mg/g TOC or <10% HC in dmmf basis) is a nonsource for major liquid hydrocarbons. A modified concept of oil-prone and non-oil-prone coal types, related to depositional environments, is proposed.

A new concept of primary migration is proposed. Accordingly, the fine-grained liptinite-rich coal network (humodetrinite-liptodetrinite) in the sapropelitic or mixinitic coal is the main area of primary migration in coal. Coal dewatering due to release of moisture (from 40% in lignite to 2% in medium volatile bituminous rank) is the main driving mechanism in hydrocarbon-phase migration from the coal network.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)