| Water—Rock Interaction in Tarim Basin：Constraints from Oilfield Water Geochemistry |
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| 引用本文： | 蔡春芳,李伟,等.Water—Rock Interaction in Tarim Basin：Constraints from Oilfield Water Geochemistry[J].中国地球化学学报,1997,16(4):289-303. |
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| 作者姓名： | 蔡春芳 李伟 |
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| 作者单位： | [1]OrganicGeochemistryLab.,JianghanPetroleumInstitute,Jingzhou434102 [2]PetroleumExploratiunandDevelopmentI,JianghanPetroleumInstitute,Jingzhou434102 |
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| 摘 要： | Olifeld waters from Cenoxoic and Mesozoic terrestrial and Paleozoic marine environments in the Tarim Basin show no obvious difference in water chemistry except Br and isotopic compositions.The Paleozoic marine strata have higher Br concentrations than the terrestrial sediments,and the lack of obvious relationship between Br and I suggests that Br is not,for the most part,derived from the degradation of organic matter.The oilfield waters are characterized by high TDS(total dissolved solids),ranging from 120000mg/L to 320000mg/L relatively low Mg,high Ca,Sr,and CF relative to Br of evaporating seawater,suggestive of enhanced water-rock interaction,OAA(organic acid anions)concentrations are generally lower than 1500mg/L with high values occurring over the temperature range from 95℃ to 140℃,in the Cambrian to Jurassic systems,and nearby unconformities.Organic acids are considered to be generated mainly from thermal maturation of kerogens during progressive burial of the Jurassic-Triassic and Cambrian-Ordovician systems,biodegradation of crude oils nearby unconformities,and thermochemical sulfate reduction in part of the Cambrian and Ordovician strata.High Al concentrations up to 3mg/L to 5.5mg/L tend to occur in the waters of high OAA or petroleum-bearing intervals,suggesting the presence of organic complexing agents.Calculation by SOLMINEQ.88 with updated database shows that AlAc^2 may account for more than 30% of the total Al.Isotopic measurements(δD,δ18O)provide evidence for the following types of waters:diagenetically-modified connate meteoric water from the Jurassic and Triassic strata;diagenetically-modified connate marine water from the Cambrian and Ordovician strata;subaerially-evaporated water from the Cenozoic and Cretaceous strata;and mixed meteoric-evaporated or/and diagenetically modified connate water from the Carboniferous strata and reservoirs adjacent to the J/C and T/C unconformities.Those waters with very negative δD values from -51.30‰to-53.80‰(SMOW) and positive δ18O values from 2.99‰to 4.99‰(SMOW)in the continuous burial of the Cambrian-Ordovician system are explained to have resulted from hydrocarbon-water and water-rock interactions.
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| 关 键 词： | 水岩反应 油田 水文地球化学 氧同位素 氢同位素 塔里木盆地 |
Water-rock interaction in Tarim Basin: Constraints from oilfield water geochemistry |
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| Chunfang Cai,Bowen Mei,Wei Li,Fangang Zeng.Water-rock interaction in Tarim Basin: Constraints from oilfield water geochemistry[J].Chinese Journal of Geochemistry,1997,16(4):289-303. |
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| Authors: | Chunfang Cai Bowen Mei Wei Li Fangang Zeng |
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| Institution: | (1) Organic Geochemistry Lab., Jianghan Petroleum Institute, 434102 Jingzhou;(2) Petroleum Exploration and Development Institute, 100083 Beijing;(3) Geology Department of Peking University, 100871 Beijing |
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| Abstract: | Oilfield waters from Cenozoic and Mesozoic terrestrial and Paleozoic marine environments in the Tarim Basin show no obvious
difference in water chemistry except Br and isotopic compositions. The Paleozoic marine strata have higher Br concentrations
than the terrestrial sediments, and the lack of obvious relationship between Br and I suggests that Br is not, for the most
part, derived from the degradation of organic matter. The oilfield waters are characterized by high TDS (total dissolved solids),
ranging from 120000 mg/L to 320000 mg/L, relatively low Mg, high Ca, Sr, and CF relative to Br of evaporating seawater, suggestive
of enhanced water-rock interaction. OAA (organic acid anions) concentrations are generally lower than 1500 mg/L with high
values occurring over the temperature range from 95°C to 140 °C, in the Cambrian to Jurassic systems, and nearby unconformities.
Organic acids are considered to be generated mainly from thermal maturation of kerogens during progressive burial of the Jurassic-Triassic
and Cambrian-Ordovician systems, biodegradation of crude oils nearby unconformities, and thermochemical sulfate reduction
in part of the Cambrian and Ordovician strata. High Al concentrations up to 3 mg/L to 5.5 mg/L tend to occur in the waters
of high OAA or petroleum- bearing intervals, suggesting the presence of organic complexing agents. Calculation by SOLMINEQ.
88 with updated database shows that AlAc2+ may account for more than 30% of the total Al. Isotopic measurements (δD, δ18O) provide evidence for the following types of waters: diagenetically-modified connate meteoric water from the Jurassic and
Triassic strata; diagenetically-modified connate marine water from the Cambrian and Ordovician strata; subaerially-evaporated
water from the Cenozoic and Cretaceous strata; and mixed meteoric-evaporated or/and diagenetically modified connate water
from the Carboniferous strata and reservoirs adjacent to the J/C and T/C unconformities. Those waters with very negative δD
values from −51.30‰ to −53.80‰ (SMOW) and positive δ18O values from 2.99‰ to 4.99‰ (SMOW) in the continuous burial of the Cambrian-Ordovician system are explained to have resulted
from hydrocarbon-water and water-rock interactions.
This project is the State Key Science and Technology Program for the “Eight Five-Year Plan” period (85-101-01-05-05). |
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| Keywords: | water-rock interaction oilfield water geochemistry hydrogen and oxygen isotopes Tarim Basin |
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