Natural bitumen (analytical review)
Classification of natural bitumen available in the world
The limited quantity of “traditional” oil reserves coupled with the increase of oil refining ratio make the worldwide oil producers and consumers of their products pay an increasingly greater attention to other types of hydrocarbons, which can partially replace the conventional oil or its heavy residues. These types of hydrocarbons include natural asphalts. According to international classifications, natural asphalt is a group of viscous and hard bitumens having specific weight of 1.0-1.1 g/cm3. They are sometimes referred to in English literature as “extraheavy oil” or “natural bitumen”. As the natural bitumens generally represent oilfield decomposition products their deposits can be encountered in virtually every oil and gas basin.
Such oil derivatives are classified into two branches. One of them includes successive naphthene oil conversion products – minerals of the asphalt family. The second branch comprises products of paraffin oil conversion – minerals of the paraffin family. The naphthene oil conversion products are in turn classified into the following three groups: asphalts, asphaltites and kerites.
The first group includes malthas and asphalts. Malthas are black and very thick resinous oils. They are rich in sulfur and oxygen. Asphalts are black or brown and black viscous and slightly elastic or hard amorphous substances (one of the world-renowned brands of natural bitumens from this group is Trinidad Lake Asphalt (TLA)).
The second group includes asphaltites which differ from asphalts by a greater hardness, fragility and higher solubility in organic solvents (one of the world-renowned brands of natural bitumen from this group is Gilsonite or North American Asphaltum). Asphaltites are rather rare minerals occurring in the form of deposits in areas where the formation of heavy naphthene oil previously occurred.
On the contrary, kerites (oil coals) do not melt or dissolve in organic solvents.
People have been familiar with natural asphalts, or natural bitumen since ancient times. Their use was described as early as in the classic literature of the Ancient East. For millennia people have been using these products to caulk their boats and manufacture waterproof dishware, treat the roofs and walls of their houses, prepare various medical infusions and mixtures, and produce printing ink, whereas natural asphalts (natural bitumen) were generally used in road surfacing since the Roman times until the present day.
Current condition of the international natural bitumen production industry.
New production processes facilitating commercially viable extraction of various hydrocarbon fractions from natural bitumen are being gradually introduced into the world practice over the last decades. Natural bitumen conversion products in their pure form or mixed with oil residues obtained by processing of conventionally produced oil are also used as raw material in the production of industrial bitumen brands. In the times of gradual depletion of conventional oil sources this new option of using a long-known natural raw material draws an increasingly greater attention of producers. In certain cases, natural bitumen can already replace “conventional” oil deposits (primarily in energy applications).
Due to the fact that natural bitumens generally represent oilfield decomposition products, their deposits occur in virtually every oil and gas basin. However, according to the latest studies the largest deposits of extraheavy oil and natural bitumens are associated with aqueous platform strata overlapping continental cratons. Elevation and erosion of such landmasses establish conditions inhibiting oil migration, which results in degradation, predominantly bacterial, of oil accumulations and the formation of extraheavy and extremely viscous natural bitumens.
Accumulations of natural bitumen characterized by various classifications, reserve and resource volumes have been discovered in many countries on almost every continent (Table 1). Unfortunately, the available literature does not provide information on individual reserves of the two aforesaid major categories of natural bitumens (asphalts and asphaltites). It appears that operating companies overlook this difference because of the fact that heat treatment of materials with similar physical properties makes such classification irrelevant
Table 1 – Natural bitumen reserves and resources (for countries with most bitumen content), billion tons
| Country | Reserves | Resources | ||
| Confirmed | initial geological |
prospective geological |
Probable | |
| Canada | 28.4 | 260.0 | 41.0 | 146.0 |
| Venezuela | 0.22-0.37 | 63.0 | 0.6 | 10.5–14.0 |
| USA | 0.01 | 6.7 | 3.15 | 23.5 |
| Trinidad and Tobago | 0.18 | – | – | 10.5 |
| Peru | – | 0.132 | – | – |
| Nigeria | 0.091 | 66.9 | – | – |
| Angola | 0.074 | 0.715 | – | – |
| Madagascar | 0.035 | 0.278 | – | – |
| Kazakhstan | 6.68 | 40.2 | – | – |
| Russia | 4.5 | – | 1.7 | |
| Indonesia | 0.067 | 1.4 | – | – |
| THE WORLD | 43.2 | 450.0 | – | 178.5 |
For instance, Pitch Lake in the Republic of Trinidad and Tobago is the most substantial commercial deposit of natural asphalts in the world. It is located in the South-West of the Island of Trinidad. The lake is 41 hectares in area and up to 76 meters in depth, and contains over 10 million tons of asphalt known throughout the world as Trinidad Lake Asphalt (TLA)
This asphalt was also used by local Indians in the Eastern part of the neighboring Venezuela for treatment of their canoes. Evidence of the long practiced use of asphalt (“pitch” in the language of Cumana Indians) has survived in legends. Industrial application of Pitch Lake asphalts was first attempted by the Spanish in late 18th century. However, large-scale development of the riches of Asphalt Lake began as late as in 1850. The Trinidad Lake Asphalt Company producing natural asphalt until the present day was founded in 1888. In 1978 it was transformed into a state company Lake Asphalt of Trinidad and Tobago, Ltd.
In 1990s the annual production of the company was approximately 20 thousand tons. About 80 % of its product is exported. Considering that the asphalt reserves of Pitch Lake are estimated at 6-10 million tons (according to various sources), they will deplete no sooner than in 400 years at the present production level. Lake Asphalt of Trinidad and Tobago, Ltd. offers a series of products for the road construction industry, in including a widely known additive for bitumen-concrete mixtures Trinidad Epuré Z 0/8 produced in the form of granules consisting of 54 % natural asphalt and 46 % mineral filler
Figure 1 – Pitch Lake in Trinidad.
Asphaltites differ from asphalts by a greater hardness, fragility and higher solubility in organic solvents. Asphaltites are rather rare minerals occurring in the form of deposits in areas where the formation of heavy naphthene oil previously occurred. The first deposit of the asphaltite group was discovered in 1860 in Utah, USA (Duchesne city in Uintah County). The first person who proposed to use the newly discovered mineral in the production of waterproof materials, as an insulation component for submarine cables and a unique lacquer was S. Gilson after whom the asphaltite from this deposit was given a trade name of Gilsonite.
The promotion of S. Gilson’s ore was so successful that in 1888 he opened a mine with a partner, and its commercial production began after the establishment of American Gilsonite Company (1904). The production reached its maximum in 1961 when it amounted to 470 thousand tons. American Gilsonite Company’s products are used in over forty, particularly European, countries of the world.
Approximately 60 thousand tons of Gilsonite are produced every year.
Figure 2 – Asphaltite samples
Presently, commercial production of natural bitumen (asphaltite) is also established in a number of other countries, but their products are not as widely known as the Trinidad asphalt and Gilsonite
The most substantial European asphalt deposit is located in Albania. Selenice asphalt deposit is located near an oil deposit of the same name. Geological reserves of natural asphalts in this deposit are estimated at 59 million tons.
Iranian asphaltite deposits are located in Kermanshah Province.
Production of asphaltite for export presently amounting to over 2000 tons per month began in 2003. The design capacity of this deposit is approximately 6000 tons a month. Its base product is crushed raw asphaltite. Primary alphaltite markets are countries of Southeast Asia, China, India, and Southern Europe. Babenna asphalt deposit in Syria is the only mined deposit in this most abundant oil region. Its annual crushed asphalt production amounts to approximately 110 thousand tons. The renowned Indonesian deposit Pasar Wajo on Buton Island (south of Sulawesi) is the largest deposit in South-East Asia. It has been developed for a rather long time and until recently supplied asphalt for road surfaces. Its annual production amounts to approximately 0.5 million tons.
