GB1454324A - Recovering combustible gases from underground deposits of coal or bituminous shale - Google Patents

Abstract

1454324 Combustible gases INSTITUT NATIONAL DES INDUSTRIES EXTRACTIVES 11 Oct 1974 [14 Aug 1974] 44065/74 Heading C5E Combustible gases are recovered from an underground deposit of coal or bituminous shale with overlying rock by thermally gasifying the coal or shale in a lower part N 1 , Fig. 1, of the deposit and recovering the combustible gases thus produced, through gasification bore S 1 , whereby the overlying rock is heated, expanded and fissured, and separately recovering, through recovery bore S 2 , the combustible constituents described and released from the rock. Gasification is carried out by repeatedly injecting air or reactive gas (hydrogen) under pressure through bore S 1 into gasification chamber C and subsequently withdrawing combustible gas therefrom. For better use of the pumping equipment two sets of gasification bores may be provided whose gasification cycles are operated out of phase. When the rocks have reached a sufficiently high temperature, a cycle in which water or steam is injected may be interposed between two cycles of gasification with air &c. so the gasification chamber C increases in size (V 1 , V 2 , V 3 ) layers of rock which form its roof disintegrate and collapse. The bottom of recovery bore S 2 is maintained at or below atmospheric pressure. Supplementary bores S 3 may be drilled to intermediate levels.