Oil shale. Prop­er­ties, dis­tri­b­u­tion, and prospects for use

Oil shale is a sed­i­men­ta­ry rock that is of great impor­tance to the ener­gy and chem­i­cal indus­tries. Due to its high organ­ic con­tent, it can pro­duce ener­gy-inten­sive prod­ucts such as shale oil, gas, and tar water. This fea­ture makes them an impor­tant raw mate­r­i­al for the pro­duc­tion of fuel, lubri­cants, and build­ing mate­ri­als. Ukraine has sig­nif­i­cant reserves of oil shale, par­tic­u­lar­ly in the Bov­tyn­skoye deposit, which opens up oppor­tu­ni­ties for ener­gy inde­pen­dence and indus­tri­al devel­op­ment.

Oil shale is includ­ed in the list of min­er­als of nation­al impor­tance approved by Res­o­lu­tion of the Cab­i­net of Min­is­ters of Ukraine No. 827 of Decem­ber 12, 1994, as a sol­id com­bustible min­er­al resource.

Properties of oil shale

Oil shale is a sed­i­men­ta­ry rock con­tain­ing 10–15% to 60–80% organ­ic mat­ter (kero­gen) of the sapro­pel or humus-sapro­pel type. They are capa­ble of burn­ing, emit­ting a spe­cif­ic odor sim­i­lar to that of burnt rub­ber. When heat­ed to 500°C with­out air access or to 1000°C with air access, organ­ic sub­stances decom­pose, form­ing shale resin (also known as shale oil), dry com­bustible gas­es, and sub-resin water.

The chem­i­cal com­po­si­tion of kero­gen includes car­bon (56–82%), hydro­gen (5.8–11.5%), nitro­gen (1–6%), sul­fur (1.5–9%), and oxy­gen (9.36%). Com­bustible shale is formed in coastal marine basins with nor­mal gas and salt water con­di­tions or in lake envi­ron­ments.

Distribution in Ukraine

In Ukraine, oil shale is wide­spread in var­i­ous tec­ton­ic struc­tures and has been found in sev­er­al regions of the coun­try. With­in the Ukrain­ian Shield (US) are locat­ed the Bov­tyn deposit and Rot­mistrivskyi occur­rence of shale asso­ci­at­ed with sed­i­men­ta­ry deposits. On the ter­ri­to­ry of the Volyn-Podil­lia Plate, shale deposits have been dis­cov­ered in the south of Podil­lia, as well as the Naslavchen­sky occur­rence in the Carpathi­ans.

The largest oil shale deposit in Ukraine is the Bov­tynske deposit, locat­ed on the bor­der of the Cherkasy and Kirovo­grad regions near the city of Olek­san­driya. It was formed in Pale­o­gene deposits that fill a fun­nel-shaped astrob­leme with a diam­e­ter of 20–25 km in the foun­da­tion of the Ukrain­ian Shield. The esti­mat­ed resources of this deposit are 3.78 bil­lion tons. The main prod­uct of extrac­tion is shale oil, which con­sists of 57% motor fuel (19% gaso­line frac­tion, 38% diesel frac­tion). For com­par­i­son, Chi­na is devel­op­ing shale with a resin yield of up to 6.9% (pro­duc­tion vol­ume – 25 mil­lion tons per year), which is ful­ly used for the pro­duc­tion of motor fuel. Thus, the devel­op­ment of the Bov­tynske deposit offers the prospect of obtain­ing up to 800 mil­lion tons of crude oil, which could sig­nif­i­cant­ly increase Ukraine’s ener­gy inde­pen­dence.

One type of com­bustible shale is menilite argillite, which is part of the Oligocene deposits of the East­ern Carpathi­ans. They cov­er an area of about 15,000 km² and are char­ac­ter­ized by high ash con­tent, low organ­ic mat­ter con­tent, and high sul­fur con­tent. The resin yield from their pro­cess­ing ranges from 1.5 to 7%, and the calorif­ic val­ue is 1177–1450 kcal/kg. Mod­ern tech­nolo­gies allow these shales to be processed to obtain gaseous prod­ucts that are used as heat car­ri­ers in heat exchange devices.

Menilite argillites are a type of bitu­mi­nous shale that is of sig­nif­i­cant indus­tri­al impor­tance. The grow­ing demand for liq­uid fuel and petro­le­um prod­ucts at the begin­ning of the 20th cen­tu­ry led to detailed stud­ies of such rocks in the Carpathi­ans, in par­tic­u­lar, Menilite shales of the Oligocene age. It is esti­mat­ed that the reserves of these shales to a depth of 100 meters in places where they come to the sur­face exceed 500 bil­lion tons.

Research con­duct­ed in the 1960s showed that menilite argillites con­tain up to 30% organ­ic mat­ter, a sig­nif­i­cant amount of sil­i­ca, and almost no car­bon­ates. When heat-treat­ed at 500–600°C, these rocks release pyrol­y­sis gas, sub-tar water, and shale oil. The lat­ter is an impor­tant raw mate­r­i­al for the chem­i­cal indus­try, from which gaso­line, kerosene, oils, and road bitu­men can be obtained.

In addi­tion to fuel use, menilite argillites have a wide range of appli­ca­tions in con­struc­tion and indus­try. They are suit­able for the pro­duc­tion of light­weight con­crete, asphalt con­crete, ceram­ic blocks, pipes, roof­ing felt, var­nish­es, and plas­tics. Sig­nif­i­cant deposits of these shales are locat­ed in the Deli­atyn field, near Yarem­che and Myku­ly­chyn, which makes them promis­ing for fur­ther indus­tri­al devel­op­ment.

The total reserves of mica schist, explored at two deposits — Deli­atyn and Verkhniosyn­ovy­den­sky in Ivano-Frankivsk and Lviv regions, amount to 4.841 mil­lion tons, of which 3.759 mil­lion tons have been con­firmed.

Deposits of com­bustible shale have also been found in Crimea. Deposits of Tau­ri­an menilite agrilites, although thin, also have a sig­nif­i­cant organ­ic con­tent and can be used as a source of ener­gy.

Uses of oil shale

Oil shale is of great impor­tance to the ener­gy and chem­i­cal indus­tries. It is used as fuel in ther­mal pow­er plants, where it pro­vides elec­tric­i­ty and heat. Dur­ing pyrol­y­sis, shale releas­es gas and liq­uid prod­ucts that can be used as heat trans­fer flu­ids in heat exchange sys­tems.

One of the most impor­tant prod­ucts of oil shale pro­cess­ing is oil shale tar. It is a valu­able raw mate­r­i­al for the chem­i­cal indus­try, as it can be used to pro­duce gaso­line, kerosene, oils, and road bitu­men. Thanks to this, oil shale is used for the pro­duc­tion of motor fuel and oth­er petro­le­um prod­ucts.

In addi­tion to ener­gy use, shale is used in con­struc­tion. It is used to make light­weight con­crete, asphalt con­crete, large ceram­ic blocks, high-qual­i­ty pipes, and roof­ing mate­ri­als, includ­ing roof­ing felt. It is also a raw mate­r­i­al for the pro­duc­tion of var­i­ous plas­tics, var­nish­es, and plas­ti­ciz­ers.

In gen­er­al, oil shale is a strate­gi­cal­ly impor­tant raw mate­r­i­al for many indus­tries. Its use allows for the pro­duc­tion of elec­tric­i­ty, motor fuel, build­ing mate­ri­als, and chem­i­cal prod­ucts. Ukraine has sig­nif­i­cant poten­tial for the devel­op­ment of oil shale deposits, which can con­tribute to the devel­op­ment of the nation­al econ­o­my and increase ener­gy secu­ri­ty. The com­pre­hen­sive devel­op­ment of deposits, in par­tic­u­lar the Bov­tyn­skyi deposit and the menilite argillites of the Carpathi­an region, is a promis­ing direc­tion for the fur­ther growth of the coun­try’s pro­duc­tion capac­i­ties.