Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
권호 표지
DOI QR코드

DOI QR Code

Geological Characteristics of Extra Heavy Oil Reservoirs in Venezuela

베네주엘라 초중질유 저류층 지질 특성

  • Kim, Dae-Suk (Department of Geology, Chungnam National University) ;
  • Kwon, Yi-Kyun (Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Chang, Chan-Dong (Department of Geology, Chungnam National University)
  • Received : 2010.11.25
  • Accepted : 2011.02.24
  • Published : 2011.02.28
Download PDF
⟨ Previous Next ⟩

Abstract

Extra heavy oil reservoirs are distributed over the world but most of them is deposited in the northern part of the Orinoco River in Venezuela, in the area of 5,500 $km^2$, This region, which has been commonly called "the Orinoco Oil Belt", contains estimated 1.3 trillion barrels of original oil-in-place and 250 billion barrels of established reserves. The Venezuela extra heavy oil has an API gravity of less than 10 degree and in situ viscosity of 5,000 cP at reservoir condition. Although the presence of extra heavy oil in the Orinoco Oil Belt has been initially reported in the 1930's, the commercial development using in situ cold production started in the 1990's. The Orinoco heavy oil deposits are clustered into 4 development areas, Boyaco, Junin, Ayachoco, and Carabobo respectively, and they are subdivided into totally 31 production blocks. Nowadays, PDVSA (Petr$\'{o}$leos de Venzuela, S.A.) makes a development of each production block with the international oil companies from more than 20 countries forming a international joint-venture company. The Eastern Venezuela Basin, the Orinoco Oil Belt is included in, is one of the major oil-bearing sedimentary basins in Venezuela and is first formed as a passive margin basin by the Jurassic tectonic plate motion. The major source rock of heavy oil is the late Cretaceous calcareous shale in the central Eastern Venezuela Basin. Hydrocarbon materials migrated an average of 150 km up dip to the southern margin of the basin. During the migration, lighter fractions in the hydrocarbon were removed by biodegradation and the oil changed into heavy and/or extra heavy oil. Miocene Oficina Formation, the main extra heavy oil reservoir, is the unconsolidated sand and shale alternation formed in fluvial-estuarine environment and also has irregularly a large number of the Cenozoic faults induced by basin subsidence and tectonics. Because Oficina Formation has not only complex lithology distribution but also irregular geology structure, geological evolution and characteristics of the reservoirs have to be determined for economical production well design and effective oil recovery. This study introduces geological formation and evolution of the Venezuela extra heavy oil reservoirs and suggest their significant geological characteristics which are (1) thickness and geometry of reservoir pay sands, (2) continuity and thickness of mud beds, (3) geometry of faults, (4) depth and geothermal character of reservoir, (5) in-situ stress field of reservoir, and (6) chemical composition of extra heavy oil. Newly developed exploration techniques, such as 3-D seismic survey and LWD (logging while drilling), can be expected as powerful methods to recognize the geological reservoir characteristics in the Orinoco Oil Belt.

베네주엘라 중앙에 위치한 오리노코강을 따라 55,000 $km^2$의 면적에 동서로 길게 자리하는 오리노코 오일벨트에는 원시부존량이 약 1조 3천억 배럴, 가채매장량이 2,500억 배럴에 달하는 초중질유가 매장되어 있다. 베네주엘라 초중질유는 API 비중이 $10^{\circ}$ 이하이고, 점성도가 5,000 cP 정도로 무겁고 점성이 큰 탄화수소 자원이다. 오리노코 지역의 초중질유는 1930년대 최초로 보고되었지만, 이들의 상업적 개발은 1990년대에 이르러 비가열식 일차생산기법을 통해서 본격적으로 이루어지기 시작하였다. 오리노코 오일벨트는 초중질유 분포 양상에 의해 보야카, 주닌, 아야쿠초, 카라보보의 생산광구로 나누어지며, 이들은 모두 31개의 생산블럭으로 소분류된다. 현재 각 생산블럭은 베네주엘라 PDVSA와 외국계 기업의 합작 형태로 개발되고 있으며, 20개국 이상이 초중질유 개발 프로젝트에 참여하고 있다. 오리노코 오일벨트는 베네주엘라의 주요 석유분지 가운데 하나인 동베네주엘라 분지의 남쪽지역에 위치한다. 동베네주엘라 분지는 쥬라기 판 분화에 의해 형성되기 시작한 수동형 대륙 주변부 분지로 그 면적은 약 120,000 $km^2$이다. 동베네주엘라 분지에서 백악기 말에 형성된 석회질 셰일은 초중질유의 주요 근원암이다. 분지 내 탄화수소는 북쪽에서 남쪽으로 평균 150 km를 이동하면서 생분해작용을 거쳤으며, 이로 인해 점성과 비중이 높은 초중질유를 분지 남쪽 경계부인 오리노코 지역에 형성하였다. 주요 초중질유 저류층인 마이오세 오피시나층은 하성-에스츄어리 퇴적환경에서 발달한 미고결 사질 및 이질이 교호하는 퇴적체이다. 또한 오피시나층은 판의 운동에 의한 압축작용과 분지침강에 의해 형성된 다수의 신생대 단층이 분포하여 복잡한 저류층 지질 특성을 나타낸다. 불균질한 저류층 암상 분포와 복잡한 지질 구조의 저류층에서 경제적인 생산정의 설계와 효율적인 초중질유 회수를 위해서는 초중질유 저류층의 발달 과정과 그로 인한 지질학적 특성에 대한 심도 깊은 이해가 필요하다. 본 연구에서는 오리노코 초중질유 저류층에서 (1) 사질 저류층 두께 및 분포, (2) 이질 퇴적층의 분포, (3) 단층의 기하학적 분포, (4) 저류층 대상 심도 및 지열 특성, (5) 저류층 지중 응력상태, (6) 초중질유의 화학적 조성 등을 초중질유 생산성에 상대적으로 큰 영향을 미치는 주요한 지질학적 특성으로 주목하였다. 이러한 오리노코 지역의 지질학적 특성들은 3차원 탄성파 탐사, 시추간 물리검층과 같은 최신 기술들을 통해 앞으로 보다 빠르고 정확하게 규명되어질 것으로 기대된다.

Keywords

Acknowledgement

Grant : 비재래형 석유저류층 지질특성 조사

Supported by : 한국지질자원연구원

References

  1. Cutis, C., Kopper, R., Decoster, E., Guzman-Garcia, A., Huggins, C., Knauer, L., Minner, M., Kupsch, N., Linares, L.M., Rough, H. and Waite, M. (2002) Heavy-Oil Reservoirs, Oil field Review, v.14, p.30-51.
  2. Diaz de Gamero, M.L. (1996) The changing course of the Orinoco River during the Neogene: a review. Paleoecology, v.123, p.385-402. https://doi.org/10.1016/0031-0182(96)00115-0
  3. Drew L.J. and Schuenemeyer J.H. (1997) Oil- and gasresources assessment in certain South American basins-An application of ARDS (ver. 5.0) to complex exploration and discovery histories, Nonrenewable Resources v.6, 4, p.295-315 https://doi.org/10.1007/BF02765928
  4. Fiorillo, G. (1987) Exploration and Evaluation of the Orinoco Oil Belt, in Exploration for Heavy Crude Oil and Natural Bitumen, Editor Meyer, R.F., AAPG Studies in Geology 25, p.103-114.
  5. Gonzalez de Juana, C., Iturralde de Arozena, J. and Picard, X. (1980) Geology of Venezuela, Its Petroliferous Basins, Foninves, p.5-300.
  6. Gonzalez, O., Ernandez, J., Chaban, F. and Bauza, L. (2006) Screening of suitable exploitation technologies on the Orinoco Oil Belt applying geostatistical methods, World Heavy Oil Conference, Beijing, China, November 12-15, 2006, Proceedings, Paper 2006-774, p.12.
  7. Head, I.M., Jones, D.M. and Larter, S.R. (2003) Biological activity in the deep subsurface and the origin of heavy oil, Nature, v.426, p.344-352. https://doi.org/10.1038/nature02134
  8. Hedberg, H.D. (1950) Geology of the Eastern Venezuela Basin, Bulletin of the Geological Society of America, v.61, p.1173-1216. https://doi.org/10.1130/0016-7606(1950)61[1173:GOTEVB]2.0.CO;2
  9. Hinkle, A. and Batzle, M. (2006) Heavy oils: a worldwide overview, The Leading Edge, v.25, p.742-749. https://doi.org/10.1190/1.2210073
  10. Isea, A. (1987) Geological synthesis of the Orinoco oil belt, Eastern Venezuela. Journal of Petroleum Geology, v.10, p.135-148. https://doi.org/10.1111/j.1747-5457.1987.tb00205.x
  11. James, K.H. (2000a) The Venezuelan Hydrocarbon Habitat, Part 1: Tectonics, Structure, Paleogeography and Source Rocks, Journal of Petroleum Geology, v.23, p.5-53. https://doi.org/10.1111/j.1747-5457.2000.tb00483.x
  12. James, K.H. (2000b) The Venezuelan Hydrocarbon Habitat, Part 2: Hydrocarbon Occurrences and Generated- Accumulated Volumes. Journal of Petroleum Geology, v.23, p.131-164.
  13. Kasper, D.A. and Larue, D.K. (1986) Paleogeographic and tectonic implications of quartzose sandstones of Barbados, Tectonics, v.5, p.837-854. https://doi.org/10.1029/TC005i006p00837
  14. Kwon, Y.K. (2008) Geology of Athabasca Oil Sands in Canada, Korean Jour. of Perol. Geol., v.14, p.1-11.
  15. Labourdette, R., Casas, J. and Imbert, P. (2008) 3D sedimentary modelling of a Miocene deltaic reservoir unit, Sincor Field, Venezuela: A new approach, Jounal of Petroleum Geology, v.21, 2, p.135-152.
  16. Martinez, A.R. (1987) The Orinoco Oil Belt, Venezuela. Journal of Petroleum Geology, v.10, p.125-134. https://doi.org/10.1111/j.1747-5457.1987.tb00204.x
  17. Ramos, M.A., Brown, J.C., Rojas, M., Kuyucu, O. and Flores, J.G. (2007) Producing extra-heavy oil from the Orinoco Belt, Cerro Negro area, Venezuela, using Bottom-Drive progressive cavity pumps, SPE Production & Operation, PAPER SPE 97889, p.151-155.
  18. Rongner, H.H. (1997) An assessment of world hydrocarbon resources. Annu. Rev. Energy Environ., v.22, p.217-262. https://doi.org/10.1146/annurev.energy.22.1.217
  19. Summa, L.L., Goodman, E.D., Richardson, M., Norton, I.O. and Green, A.R. (2003) Hydrocarbon systems of Northeastern Venezuela: plate through molecular scale-analysis of the genesis and evolution of the Eastern Venezuela Basin. Marine and Petroleum Geology, v.20, p.323-349. https://doi.org/10.1016/S0264-8172(03)00040-0
  20. Talukdar, S.C., Gallango, O. and Ruggeiro, A. (1987) Generation and migration of oil in the Maturin Subbasin, Eastern Venezuelan Basin. Organic Geochemistry, 13, p.537-547.
  21. Tankersley, T.H. and Waite, M.W. (2002) Reservoir modeling for horizontal exploitation of a giant heavy oil field - Challenges and lessons learned, SPE/PS-CIM/CHOA International Thermal Operations and Heavy Oil Symposium and International Horizontal Well Technology Conference 2002, Alberta, Canada.
  22. USGS (2009) An estimate of recoverable heavy oil resources of the Orinoco oil belt, Venezuela. Fact Sheet 2009-3028.