The Outlook for Shale Oil
Authors: Culberson S. Frank 
Published: December 2007

Distinguished Author Series articles are general, descriptiverepresentations that summarize the state of the art in an area of technology bydescribing recent developments for readers who are not specialists in thetopics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and presentspecific details only to illustrate the technology. Purpose: to informthe general readership of recent advances in various areas of petroleumengineering.

Introduction

Recent world energy events have focused increased attention on syntheticfuels. Synthetic fuels represent a source of energy to reduce dependence onimported petroleum and a long-term source of hydrocarbons to cover potentialshortfalls. Shale oil appears to be the most attractive potential shortfalls.Shale oil appears to be the most attractive synthetic fuel alternative andclearly is emerging as the first synthetic fuel to be produced in largequantities. The U.S. has significant reserves of oil shale but has producedrelatively little to date. The production of oil from the pyrolysis of thekerogen in oil shale, however, has been practiced in different localities forhundreds of years. Oil shale is in fact the world's most commonly occurringfossil fuel resource; early records of its use may be found in many countries.Sizable industries once existed or still do in Australia, China, the USSR, Sweden, Scotland, France, and Spain. There has been some continuing interest;however, the era of cheap crude oil for the first 70 years of this centuryeffectively limited interest in shale oil production, particularly in the U.S., until the oil embargo and the sharp petroleum particularly in the U.S., untilthe oil embargo and the sharp petroleum price increases in 1979 and 1980. priceincreases in 1979 and 1980. A number of U.S. shale oil developers are active, even though the project status and predicted dates for commercial productionfrequently project status and predicted dates for commercial productionfrequently change. Table 1 presents a list of potential developers (which forthe most part are major energy companies), the announced production level forthe first commercial plants, and possible on-stream dates. The projects underdevelopment show shale oil production of 269,000 B/D by 1990 and 574,000 B/D by1992. The 1990 and 1992 forecasts may be higher or lower, depending on the rateof development over the next several years.

The Oil Shale Resource

Oil shale is a fine-grained sedimentary rock containing a solid organicmaterial called kerogen. Kerogen is of high molecular weight and has lowsolubility in any solvent. However, hydrocarbons can be recovered from oilshale simply by heating the rock to high temperatures. Early developmentsaround the world resulted from this feature and did not use or requiresophisticated equipment or processes. When oil shale is heated to temperaturesnear 900 to 950F, the solid kerogen pyrolyzes, yielding gaseous and liquidproducts and leaving behind a soiled carbonaceous residue. This happens whetherthe heating time is seconds or hours, whether it is done at ambient or elevatedpressures, whether the heating atmosphere is any of a variety of gases, whetherthe heat transfer medium is gaseous or solid, and whether the heat istransferred by conduction, convection, or radiation. In short, it is easy topyrolize oil shale. Therefore, the conversion process for oil shale istechnically much simpler than coal gasification or process for oil shale istechnically much simpler than coal gasification or liquefaction, which involvemore difficult reactions at more severe operating conditions. The single mostimportant chemical reason for this difference is the higher carbon/hydrogenratio in oil shale. This ratio varies widely from one oil shale deposit toanother and is the major factor determining the efficiency of the recoveryprocess. The U.S. reserves of oil shale are enormous. It has been estimatedthat an equivalent of 7 trillion bbl oil are contained in U.S. reserves. Nearly60% of this total is in the relatively rich Green River formation in westernColorado, eastern Utah, and southern Wyoming (Fig. 1). The remainder is in theleaner Devonian-Mississippian black shale deposits that underlie primarilyIndiana, Ohio, Illinois, Kentucky, Tennessee, Michigan, and Pennsylvania.Eastern shales are of considerably lower quality than western shales and have apoorer carbon/hydrogen ratio.

JPT

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