Origin and evolution of formation water from the Ordovician carbonate reservoir in the Tazhong area, Tarim Basin, NW China
Origin and evolution of formation water from the Ordovician carbonate reservoir in the Tazhong area, Tarim Basin, NW China
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塔里木盆地塔中地区奥陶系碳酸盐岩储层水成因及演化
DOI：
10.1016/j.petrol.2016.10.016
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发表时间：
2017-01-01
影响因子：
--
通讯作者：
Cai, Chunfang
中科院分区：
文献类型：
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作者：
Li, Hongxia;Cai, Chunfang
对塔里木盆地塔中地区奥陶系碳酸盐岩储层地层水的化学、氢、氧、锶同位素进行了测定。目的是通过热化学硫酸盐还原(TSR)和水-岩相互作用来阐明它们的起源和迁移以及它们的变化。与海水蒸发轨迹(SET)相比，海水来源于蒸发海水，富Ca、Sr，亏损Mg、SO4，为白云石化、硬石膏溶解和原位TSR的结果。由于水-岩相互作用，Delta O-18值呈正移，而Delta D值随TSR程度或伴生原油中硫金刚烷总浓度的增加而负移，可能是由于与TSR-H_2S的氢同位素交换所致。而三角洲D-O-18关系主要受控于与古大气水的混合，其中D为-50%，O-18为-7.5%。古大气水可能淋滤了志留系硅质碎屑岩，因此其锶-87/锶-86高达0.715。上奥陶统(O(3)L)地层水比O(1-2)y水具有更多的负增量D和增量O-18值，更高的SR-87/SR-86比值和更低的总溶解固体(TDS)，这可能是古大气降水混合的结果。下奥陶统(O(1-2)y)地层水的锶-87/锶-86比值为0.7095~0.7105，TDS为160~240g/L，锶含量为300~1000 mg/L，可能是与埃迪卡拉系和下寒武统硅屑岩上移的热液混合作用的结果。1号断坡带以东的古高地和10号构造带附近的活动断裂带分别与古大气水和热液发生了显著的混合。在10号构造带中，热液流体和油气可能具有相似的运移路径。因此，地层水地球化学可能为制约石油运移提供线索。
Chemistry, H, O and Sr isotopes of formation waters were determined from the Ordovician carbonate reservoirs in the Tazhong area, Tarim basin. The aim is to elucidate their origin and migration and their alteration by thermochemical sulfate reduction (TSR) and water-rock interactions. The waters were originated from evaporated seawater, and are enriched in Ca and Sr, and depleted in Mg and SO4 compared with the seawater evaporation trajectory (SET), thus are considered to result from dolomitization, anhydrite dissolution and in situ TSR. delta O-18 values show positive shift due to water-rock interactions, and delta D values show negative shift with increasing TSR extents or total thiaadamantanes concentrations of the associated oils, likely resulting from hydrogen isotope exchange with TSR-H2S. However, the delta D-delta O-18 relationship was mainly controlled by the mixing with paleo-meteoric water with delta D of -50% and delta O-18 of -7.5%. Paleo-meteoric water may have leached the Silurian siliciclastic rocks and thus has Sr-87/Sr-86 up to 0.715. Upper Ordovician (O(3)l) formation water shows more negative delta D and delta O-18 values, higher Sr-87/Sr-86 ratios and lower total dissolved solids (TDS) than the O(1-2)y water, which may have resulted from mixing of paleo-meteoric water. Lower Ordovician (O(1-2)y) formation water shows Sr-87/Sr-86 ratio of 0.7095-0.7105, TDS from 160 to 240 g/l, and Sr concentrations from 300 to 1000 mg/L, which may have resulted from mixing with hydrothermal fluid up-migrated from Ediacaran and Lower Cambrian siliciclastic rocks. Significant mixings with paleo-meteoric water and hydrothermal fluid occurred at paleo-highland at the east of No. 1 Fault-Slope Zone and active faulting zone near No. 10 Structural Belt, respectively. Hydrothermal fluid and oils probably shared similar migration pathways in No. 10 Structural Belt. Formation water geochemistry may thus provide clues to constraint on petroleum migration.