The Tahe oil field ( zh, 塔河油田) is an

oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the prese ...

located in

Xinjiang Xinjiang,; , SASM/GNC romanization, SASM/GNC: Chinese postal romanization, previously romanized as Sinkiang, officially the Xinjiang Uygur Autonomous Region (XUAR), is an Autonomous regions of China, autonomous region of the China, People' ...

. It was discovered in 1990 and developed by

China National Petroleum Corporation The China National Petroleum Corporation (CNPC) () is a major national oil and gas corporation of China and one of the largest integrated energy groups in the world. Its headquarters are in Dongcheng District, Beijing, Dongcheng District, Beij ...

. It began production in 1990 and produces

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) and lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...

. The total

proven reserves Proven reserves (also called measured reserves, 1P, and reserves) is a measure of fossil fuel energy reserves, such as oil and gas reserves and coal reserves. It is defined as the "quantity of energy sources estimated with reasonable certaint ...

of the Tahe oil field are around 4.26 billion barrels (600 million tonnes), and production is centered on . The Tahe oil field is a part of the Akekule Arch which is located in the North Uplift of the

Tarim Basin The Tarim Basin is an endorheic basin in Xinjiang, Northwestern China occupying an area of about and one of the largest basins in Northwest China.Chen, Yaning, et al. "Regional climate change and its effects on river runoff in the Tarim Basin, Ch ...

. This area experienced two events of

karstification Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. There is some eviden ...

which affected the

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

strata. The paleokarst reservoirs constituting the Tahe oil field were mostly formed by the younger, early

Hercynian Hercynia is a name for the ancient Hercynian Forest. Hercynia or Hercynian may also refer to: *458 Hercynia, an asteroid *Hercynian orogeny, a synonym for the Variscan orogeny The Variscan orogeny, or Hercynian orogeny, was a geologic mountai ...

karstification. The oil field contains multiple

caves Caves or caverns are natural voids under the Earth's surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance underground (such as rock ...

filled with

sediments Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

, collapse

breccias Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a varie ...

, and chemical fills. Sediments and collapsed breccias are characteristic for the reservoir run-off zone, whereas

vadose zone The vadose zone (from the Latin word for "shallow"), also termed the unsaturated zone, is the part of Earth between the land surface and the top of the phreatic zone, the position at which the groundwater (the water in the soil's pores) is at ...

is characterized by high-angle fractures and epikarst zone is characterized by

weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

residues and dissolution

fractures Fracture is the appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress (mechanics), stress. The fracture of a solid usually occurs due to the development of certain displacemen ...

. The paleogeomorphological results indicate that paleokarst structures formed mostly in highlands and slopes during the Hercynian karstification event.

References

Oil fields in China {{PRChina-geo-stub