Ac­cess­ing geothermal wa­ter via aban­doned oil and gas wells

Canadian Geographic - - CONTENTS - By Sab­rina Doyle Teachers! Bring this and other sci­en­tific in­no­va­tions into your class­room by vis­it­ing can­geoe­d­u­ca­­sources.

Res­ur­rect­ing aban­doned oil wells for geothermal heat­ing in Hin­ton, Alta.

TTrans­form­ing aban­doned oil and gas wells in Al­berta into the key com­po­nents of a firstof-its-kind geothermal heat­ing sys­tem in Canada might seem like an im­plau­si­ble trans­for­ma­tion — but that’s ex­actly what could hap­pen in fewer than two years in Hin­ton. The town of about 10,000 just out­side of Jasper Na­tional Park sits atop reser­voirs of wa­ter that at 140 C and five kilo­me­tres be­low the sur­face are some of the hottest and deep­est in the province. And although it’s not un­com­mon in Canada to use geoex­change sys­tems (a type of ground-source heat pump) to heat and cool in­di­vid­ual build­ings, Hin­ton wants to tap into that ther­mal en­ergy on a much wider scale by im­ple­ment­ing a district geothermal heat­ing sys­tem that uses heat re­cov­ered from dis­used oil and gas wells. Fund­ing isn’t com­pletely in place and reg­u­la­tory frame­works have yet to be de­ter­mined, but work could be­gin by 2019 on the sys­tem, which would heat pub­lic build­ings — in­clud­ing the hospi­tal, the RCMP sta­tion and two schools — in a town that largely re­lies on nat­u­ral gas.

GEOTHERMAL GE­OG­RA­PHY Hin­ton’s ge­og­ra­phy is the key to its geothermal po­ten­tial. The lay­ered rock for­ma­tions of the Western Cana­dian Sed­i­men­tary Basin and the frac­tured rock of the Rocky Moun­tain Trench nat­u­rally trap the hot, briny wa­ter. Rang­ing from 70 C to 175 C, the wa­ter in the aquifers be­neath Hin­ton has some of the high­est tem­per­a­tures mea­sured any­where in the Al­berta Basin, the deep­est stretch of the Western Cana­dian Sed­i­men­tary Basin.


A geothermal reser­voir (1) is cre­ated when hot wa­ter or steam is trapped in cracks and pores un­der a layer of im­per­me­able rock. In a power plant, the wa­ter or steam is trans­ported to the sur­face to drive a tur­bine. Some­times, how­ever, the wa­ter or steam is used solely as a heat source.


Hin­ton has part­nered with the Univer­sity of Al­berta’s Fu­ture En­ergy Sys­tems re­search group and Epoch En­ergy, a geother­malen­ergy devel­op­ment com­pany, to choose 14 aban­doned wells, the ma­jor­ity of which are about 2,500 me­tres deep, as vi­able can­di­dates for the sys­tem. The next stage of the study will more specif­i­cally weigh the pros and cons of each, such as its prox­im­ity to town, the ex­ist­ing in­fra­struc­ture that sur­rounds it and its sta­bil­ity.

THE BEN­E­FITS Res­ur­rect­ing aban­doned wells for geothermal use would re­duce green­house gas emis­sions and help pro­tect peo­ple from the costs as­so­ci­ated with an un­pre­dictable en­ergy com­modi­ties mar­ket. The typ­i­cal Cana­dian home uses about 120 gi­ga­joules per year, but Hin­ton’s sys­tem could pro­vide be­tween 60,000 and 100,000 gi­ga­joules per year, enough to heat be­tween 500 and 800 homes.


Spe­cific en­gi­neer­ing de­tails haven’t been con­firmed, but the pre­lim­i­nary net­work model would pipe hot wa­ter to se­lect pub­lic build­ings through a se­ries of closed loops. The first loop would bring the nat­u­rally heated wa­ter through a pro­duc­tion well (2) and into a heat ex­change unit (3), where it would heat sep­a­rate, in­ert wa­ter. That wa­ter would then cir­cu­late through the pub­lic build­ings (4) in a sec­ond loop be­fore it cools and is re­turned to the reser­voir via an in­jec­tion well (5) to start the process all over again.

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