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 presence ...

located in

Xinjiang Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwest ...

. 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. CNPC was ranked fourth ...

. 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) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

. The total

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

of the Tahe oil field are around 4.26 billion barrels (600×10⁶tonnes), 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 Northwest 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, China." Hydr ...

. This area experienced two events of

karstification Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...

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. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

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

Hercynian The Variscan or Hercynian orogeny was a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea. Nomenclature The name ''Variscan'', come ...

karstification. The oil field contains multiple

caves A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...

filled with

sediments Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand a ...

, 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 variety of di ...

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

vadose zone The vadose zone, 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 atmospheric pressure ("vadose" is fr ...

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, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

residues and dissolution

fractures Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displa ...

. 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