Effects of abnormally high heat stress on petroleum in reservoir |
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Authors: | DongYa Zhu ZhiJun Jin WenXuan Hu XueFeng Zhang |
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Institution: | (1) Petroleum Exploration and Production Institute, China Petroleum & Chemical Corporation, Beijing, 100083, China;(2) Department of Earth Sciences, Nanjing University, Nanjing, 210093, China;(3) School of Resource and Information, China University of Petroleum, Beijing, 102249, China |
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Abstract: | An igneous intrusion of 94m thick was discovered intruding into the Silurian sandstone from Tazhong 18 Well. The petroleum
previously preserved in the Silurian sandstone reservoir was altered into black carbonaceous bitumen by abnormally high heat
stress induced by the igneous intrusion. The reflectance of the carbonaceous bitumen reaches as high as 3.54%, indicating
that the bitumen had evolved into a high thermal evolution level. Similar to the Silurian samples from the neighboring Tazhong
11, Tazhong 12, Tazhong 45 and Tazhong 47 wells, the distribution of C27, C28 and C29 steranes of the carbonaceous bitumen is still “V”-shaped and can still be employed as an efficient parameter in oil source
correlation. The “V”-shaped distribution indicates that the hydrocarbons from the Tazhong 18 and the neighboring wells were
all generated from the Middle-Upper Ordovician hydrocarbon source rocks. However, the oil source correlation parameters associated
with and terpanes had been changed greatly by the high heat stress and can no longer be used in oil source correlation. The
δ
13C values of the petroleum from the neighboring wells are between −32.53%. and −33.37%., coincident with those of the Paleozoic
marine petroleum in the Tarim Basin. However, the δ
13C values of the carbonaceous bitumen from the Tazhong 18 Well are between −27.18%. and −29.26%., isotopically much heavier
than the petroleum from the neighboring wells. The content of light hydrocarbons (nC14−nC20) of the saturated hydrocarbon fraction in the carbonaceous bitumen is extremely higher than the content of heavy hydrocarbons.
The light/heavy hydrocarbon ratios (ΣnC21
−/ΣnC22
+ are between 4.56 and 39.17. In the saturated fraction, the even numbered hydrocarbons are predominant to the odd numbered,
and the OEP (Odd to Even Predominance) values are between 0.22 and 0.49. However, the content of light hydrocarbons in the
petroleum from the neighboring wells is relatively low and the content of the even numbered hydrocarbons is almost equal to
that of the odd numbered. Compared with the samples from the neighboring wells, the abundance of non-alkylated aromatic hydrocarbons,
such as phenanthrenes, and polycyclic aromatic hydrocarbons (PAHs), such as fluoranthane, pyrene, benzoa]anthracene and benzofluoranthene,
are relatively high.
Supported by the National Key Basic Research and Development Project (Grant No. 2005CB422103) |
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Keywords: | Tarim Basin igneous intrusive abnormally high heat stress bitumen carbon isotope PAH |
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