US 4,552,214 AGranted

Pulsed in situ retorting in an array of oil shale retorts

AssigneesStandard Oil Company (Indiana), Gulf Oil Corporation

InventorsJohn M. Forgac, George R. Hoekstra

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Abstract

Greater product yield and quality and continuous upgrading of shale oil with hydrogen-rich, purge mode off gases is attained by pulsing in situ retorts at different phases and intervals. In the process, flow of feed gases to the flame fronts of underground retorts are sequentially stopped and purged while continuously retorting the oil shale to enhance transfer of sensible heat from the combustion zones to the retorting zones and enlarge the separation between the combustion zones and the advancing fronts of the retorting zones. The flame fronts can be purged with steam, water, carbon dioxide, nitrogen, hydrogen, combustion mode off gases, purge mode off gases, reactor off gases, or combinations thereof. The combustion mode off gases and/or purge mode off gases can also be used as part of the feed gas or fuel gas.

Claims27

Dependent claims

A process for retorting oil shale, comprising the steps of:

(a) simultaneously heating rubblized masses of oil shale in retorting zones of a plurality of underground retorts to a retorting temperature to liberate hydrocarbons and water from said oil shale leaving retorted shale containing residual carbon;
(b) combusting said residual carbon in said oil shale in combustion zones behind said retorting zones in said plurality of underground retorts with flame fronts fed by a feed gas to provide a substantial portion of said heating, said flame fronts advancing generally in the direction of flow of said feed gas;
(c) injecting a purge fluid selected from the group consisting essentially of steam, water, nitrogen, carbon dioxide, and combinations thereof, into said plurality of underground retorts to quench said flame fronts and subsequently reigniting said flame fronts with said feed gas while continuing to liberate hydrocarbons and water in said retorting zone;
(d) step (b) being performed in at least one of said underground retorts at a time when step (c) is performed in at least one other of said underground retorts;
and
(e) withdrawing said liberated hydrocarbons and water from said underground retorts.

3 more elements

A process for retorting oil shale, comprising the steps of:

(a) forming a series of generally upright modified in situ underground oil shale retorts in subterranean formations of raw oil shale by
removing from 2% to 40% by volume of said oil shale from said formations leaving cavities therein,
transporting said removed shale to a location above ground for surface retorting, and
explosively rubblizing masses of said oil shale substantially surrounding said cavities to form said series of underground retorts;
(b) igniting a flame front generally across each of said retorts with a fuel gas;
(c) pyrolyzing portions of said rubblized raw oil shale in a retorting zone in each of said underground retorts to liberate shale oil off gases and raw retort water from said raw oil shale leaving retorted shale containing residual carbon, said raw retort water containing oil shale particulates, shale oil, ammonia, and organic carbon;
(d) advancing said retorting zone generally downwardly in each of said underground retorts;
(e) combusting residual carbon on said retorted shale in a combustion zone above said retorting zone in each of said underground retorts with a flame front;
(f) alternately injecting a flame front-supporting feed fluid and a frame front-extinguishing purging fluid selected from the group consisting essentially of steam, purified water, and raw retort water containing oil shale particulates, shale oil, ammonia, and organic carbon, into each of said combustion zones while continuing step (d), said flame front-supporting feed fluid supporting, igniting and propelling said flame front generally downwardly to define a combustion mode of operation, said flame front-extinguishing purging fluid extinguishing said flame fronts and accelerating transfer of sensible heat from said combustion zone to said retorting zones to define a purge mode of operation;
(g) alternating operating some of said underground retorts in a combustion mode while operating other of said underground retorts in a purge mode and vice versa;
and
(h) withdrawing said liberated shale oil, off gases, and raw retort water from said series of underground retorts.

9 more elements

Dependencies are inferred from the claim text.