• The Korean Journal of Petroleum Geology
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• v.14 no.1
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• pp.36-44
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• 2008

Natural gas in tight reservoirs, one of unconventional hydrocarbon resources, has become a significant exploration and exploitation targets. Tight gas reservoirs are the gas-bearing rocks that commonly have a permeability of less than 0.1 millidarcy (mD). Tight gas reservoirs are characterized by extensive and deep locations as well as abnormal pressure such as over- or under-pressure. The tight gas reservoirs are independent of structural or stratigraphic traps, whereas conventional gases normally occur at these traps. Tight gas reservoirs can be productive when stimulated by hydraulic fracturing. Better production areas within the tight reservoir beds are referred to as sweet spots that are commonly caused by natural fractures, which should be understood and identified to enhance the recovery of the gas from tight reservoirs. The exploration and production techniques allow the commercial production of tight gas, one of environmentally friendly resources. Slant and horizontal wells have best production when they intersect the fractures. Gas production from the tight reservoirs has rapidly grown in U.S. and Canada. Indeed, the U.S. gas production of tight sandstones increases from 11.1% in 1990 to 24.1% in 2005. The presence of tight gas reservoirs has been suggested on the Korean offshore block 6-1. Paradigm shift from conventional to unconventional tight reservoir is required to develop the tight gas from the block.

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.109-116
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• 2007

As conventional light oil resources deplete, it is becoming necessary to develop unconventional resources. To meet the demand for petrochemical industry, heavier sources such as heavy oil and bitumen are being utilized. Bitumens, a complex hydrocarbon made up of a long chain of molecules, are found in oil sand. It is estimated that 830 billion barrels of oil are located in the oil sand in Alberta, Canada. This paper will review briefly (1) the basic concept of oil sand, bitumen, and heavy oil, (2) methods how to extract oil from oil sand, (3) methods how to upgrade to synthetic crude oil, and (4) economic evaluation of technology.

• Resources Recycling
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• v.17 no.6
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• pp.62-67
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• 2008

Oil shale is a sedimentary rock that contains organic compounds called kerogen that are released as petroleum-like liquids by retorting. In order to evalute oil shale as alternative oil resources, the physical properties of oil shale samples from US and Russia were investigated and Fischer assays were carried out. Thermogravimetric analysis shows that thermal degradation of oil shale consisted of two stage processes, with hydrocarbon release from kerogen followed by $CO_2$ release by carbonate decomposition. Organic compounds in oil shale have an high hydrogen/carbon ratio, and therefore liquid hydrocarbons could be obtained easily. Shale oil yields from Russian and US oil shales by Fischer assay were 12.7% and 18.5%, respectively. The density and boiling point of shale oils are higher than that of Middle East crude oil, indicating that further upgrading processes are necessary for refinery. On the other hands, sulfur contents are relatively low, and the amounts of Vanadium and Nickel are extremely small in shale oil. It was found that paraffins were rich in US shale oil while main components of Russian shale oil were oxygenated hydrocarbons.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.343-352
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• 2016

It has been estimated that the Earth has nearly 1.688 trillion barrels of crude oil, which will last 53.3 years at current extraction rates. The organization of petroleum exporting countries (OPEC) group forecasted that the oil prices will not jump to triple-digit territory within a decade, but it can quickly increase as the political issue for reducing oil production appears. With the potential of serious shortage of conventional hydrocarbon resources, the heavy oil, one of unconventional hydrocarbon resources including oil sand and natural bitumen has attracted worldwide interest. The heavy oil contains heavy hydrocarbon compounds, commonly called as resins and asphaltenes, with long carbon chains more than sixty carbon atoms. The high content of heavier fraction corresponds with the high molecular weight, viscosity, and boiling point. Physicochemical properties of residues from vacuum distillation of conventional oil, referred to as vacuum residues (VR) were similar to those of heavy oil. For the development of heavy oil reserves, reducing the heavy oil viscosity is the most important. In this article, commercially employed aquathermolysis processes and their application to VR upgrading are discussed. VR contains transition metals such as Ni and V, but these metals should be eliminated in advance for further refining. Recent studies on demetallization technologies for VR are also reviewed.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.660-669
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• 2018

Enhanced oil recovery (EOR) is a method used to improve the recovery factor of remaining hydrocarbon in reservoir. Polymer and surfactant EOR techniques have limitations depending on reservoir or production conditions (temperature, salinity, etc.) because the polymer and surfactant are highly affected by the reservoir conditions. In this study, analysis of the current improvements to chemical substances and application technologies was performed based on recent research data. Conventional polymer is readily degraded by the conditions of high temperature and high salinity. Therefore, new polymers and injection techniques have been developed to remediate such problems. In addition, surfactant applicable to shale and carbonate reservoirs is developed as petroleum recovery expands to unconventional reservoirs. However, these chemical substances are not widely used in the current oil fields due to high costs. Therefore, further studies must be conducted to reduce the cost and thus increase the effectiveness of EOR techniques.

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.28-46
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• 2001

Natural gas is a mixture of hydrocarbon gases and impurities such as nitrogen, hydrogen sulfide, and carbon dioxide and a clean energy producing no pollution materials for combustion. Currently, the demand of the natural gas is rapidly increasing due to worldwide environmental problems. According to Hubbert's study in the past, the natural gas was predicted as rapidly depleted resources, and then the results led to high gas price and limitation of usage during 1980s. Afterward, the study of natural gas resources based on geology identified the additional natural gas resources that were not considered in Hubbert's study. They are unconventional gas, additional resources in the existed reservoirs, and natural gas in deep subsurface areas. Such additional resouces made the future of natural gas bright and pormised low and stable gas price in the future. Deep natural gas is defined as the gas existing at or below 15,000ft$(4,752{\cal}m)$ in depth from the surface. According to the study from the U.S. Geological Survey(USGS) in 1995, 1,412 TCF of technically recoverable natural gas was remained to be discovered or developed in the onshore of United States. A significant part of that resource base, 114 TCF, exists at deep sedimentary basins, and it shows wide distribution with various geological environments. In 1995, the deep gas contributed to $6.7\% of total supply amount of natural gas in the United States and is expected to be $18.7\% by 201.5. However, the development of the deep gas is a high risky business due to expensive investment and high portion of dry holes, although it is developed. Thus, for developing the deep gas economically, it is necessary to overcome many technical challenges. In this paper, for increasing success rate of the deep gas, 1) geologic and compositional characteristics, and production cost have been analyzed according to depth, 2) technical problems related to deep gas production have been summarized, and 3) finally future study areas for increasing application of the deep gas have been suggested. For reference, this paper was written based on the study results from USGS and Gas Research Institute(GRI), for the United States is doing the most active R&D in the deep gas area, and thus, has many reliable data.

• The Korean Journal of Petroleum Geology
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• v.14 no.1
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• pp.1-11
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• 2008

As conventional oil and gas reservoirs become depleted, interests for oil sands has rapidly increased in the last decade. Oil sands are mixture of bitumen, water, and host sediments of sand and clay. Most oil sand is unconsolidated sand that is held together by bitumen. Bitumen has hydrocarbon in situ viscosity of >10,000 centipoises (cP) at reservoir condition and has API gravity between $8-14^{\circ}$. The largest oil sand deposits are in Alberta and Saskatchewan, Canada. The reverves are approximated at 1.7 trillion barrels of initial oil-in-place and 173 billion barrels of remaining established reserves. Alberta has a number of oil sands deposits which are grouped into three oil sand development areas - the Athabasca, Cold Lake, and Peace River, with the largest current bitumen production from Athabasca. Principal oil sands deposits consist of the McMurray Fm and Wabiskaw Mbr in Athabasca area, the Gething and Bluesky formations in Peace River area, and relatively thin multi-reservoir deposits of McMurray, Clearwater, and Grand Rapid formations in Cold Lake area. The reservoir sediments were deposited in the foreland basin (Western Canada Sedimentary Basin) formed by collision between the Pacific and North America plates and the subsequent thrusting movements in the Mesozoic. The deposits are underlain by basement rocks of Paleozoic carbonates with highly variable topography. The oil sands deposits were formed during the Early Cretaceous transgression which occurred along the Cretaceous Interior Seaway in North America. The oil-sands-hosting McMurray and Wabiskaw deposits in the Athabasca area consist of the lower fluvial and the upper estuarine-offshore sediments, reflecting the broad and overall transgression. The deposits are characterized by facies heterogeneity of channelized reservoir sands and non-reservoir muds. Main reservoir bodies of the McMurray Formation are fluvial and estuarine channel-point bar complexes which are interbedded with fine-grained deposits formed in floodplain, tidal flat, and estuarine bay. The Wabiskaw deposits (basal member of the Clearwater Formation) commonly comprise sheet-shaped offshore muds and sands, but occasionally show deep-incision into the McMurray deposits, forming channelized reservoir sand bodies of oil sands. In Canada, bitumen of oil sands deposits is produced by surface mining or in-situ thermal recovery processes. Bitumen sands recovered by surface mining are changed into synthetic crude oil through extraction and upgrading processes. On the other hand, bitumen produced by in-situ thermal recovery is transported to refinery only through bitumen blending process. The in-situ thermal recovery technology is represented by Steam-Assisted Gravity Drainage and Cyclic Steam Stimulation. These technologies are based on steam injection into bitumen sand reservoirs for increase in reservoir in-situ temperature and in bitumen mobility. In oil sands reservoirs, efficiency for steam propagation is controlled mainly by reservoir geology. Accordingly, understanding of geological factors and characteristics of oil sands reservoir deposits is prerequisite for well-designed development planning and effective bitumen production. As significant geological factors and characteristics in oil sands reservoir deposits, this study suggests (1) pay of bitumen sands and connectivity, (2) bitumen content and saturation, (3) geologic structure, (4) distribution of mud baffles and plugs, (5) thickness and lateral continuity of mud interbeds, (6) distribution of water-saturated sands, (7) distribution of gas-saturated sands, (8) direction of lateral accretion of point bar, (9) distribution of diagenetic layers and nodules, and (10) texture and fabric change within reservoir sand body.