石油与天然气地质 ›› 2006, Vol. 27 ›› Issue (1): 85-92.doi: 10.11743/ogg20060114

• 区域地质构造与油气评价 • 上一篇    下一篇

塔里木盆地东北部奥陶-志留系沉积成岩作用

郑冰1,2, 承秋泉2, 高仁祥2   

  1. 1. 成都理工大学,四川,成都,610059;
    2. 中国石化,石油勘探开发研究院,无锡石油地质研究所,江苏,无锡,214151
  • 收稿日期:2005-09-23 出版日期:2006-02-25 发布日期:2012-01-16

Ordovician-Silurian sedimentation and diagenesis in northeastern Tarim basin

Zheng Bing1,2, Cheng Qiuquan2, Gao Renxiang2   

  1. 1. Chengdu University of Technology, Chengdu, Sichuan 610059, China;
    2. Institute of Petroleum Geology, Exploration and Production Research Institute, SINOPEC, Wuxi, Jiangsu 214151, China
  • Received:2005-09-23 Online:2006-02-25 Published:2012-01-16

摘要:

塔里木盆地东北地区奥陶系为一套粉砂质泥岩和灰岩;志留系砂砾岩构成4个沉积旋回,为典型的复理石建造,含油气层位于旋回的底部,4个旋回均已倒转。成岩作用在埋深1500 m已很显著,富含大气CO2水中沉淀亮晶方解石(Ⅰ),δ13c为-4‰-6‰,δ180为-5‰~-6‰。埋深2400-2600 m,硫酸盐还原带形成的碳酸盐(Ⅱ)δ13C为-7‰~-10‰,δ18O为-8‰~-10‰,长石溶解形成第一次生孔隙带。埋深3800-4000 m,甲烷生成带脱羧作用产生的CH4形成波状消光白云石 (Ⅲ),δ13C为-1‰~-16‰,而CO2直接形成的碳酸盐δ13C为20‰右右,δ18O均在-12‰~-13‰,SiO2次生包体测温110-120℃,形成第二次生孔隙带。埋深4500-4700 m为湿气生成带,形成的碳酸盐(Ⅳ)δ13C为-27‰~-31‰,δ18O为-13‰~-14‰,包体测温130-140℃,含铁方解石大量溶解形成第三次生孔隙带。埋深达到5000 m以上时产生大量干气(Ⅴ), δ13C为-18‰~-20‰,δ18O为-1‰~-14‰,与包体均一温度150-155℃相一致,形成第四次生孔隙带,孔隙度仅15%-20%。海西运动期间褶皱地层可能倒转,抬升剥蚀可能达5000 m左右,接着发生"退成岩作用"。

关键词: 包裹体均一温度, 次生孔隙带, 同位素, 世代, 碳酸盐胶结物, 奥陶-志留系, 塔里木盆地东北部

Abstract:

The Ordovician is composed of silty mudstone and limestone, and the Silurian is a typical flysch formation composed of four depositional cycles of glutinite in the northeastern Tarim basin. The reservoirs occur at the bottom of each cycle. All of the 4 cycles have been inverted. Diagenesis is obvious at a depth of 1 500 m where sparry calcite (Ⅰ) has been precipitated from water rich in atmospheric CO2 with δ13C in the range of -4‰ and -6‰, and 818O in the range of -5‰ and -6‰. At a burial depth of 2 400-2 600 m, δ13C and δ18O in the carbonate (Ⅱ) formed in the sulfate reduction zone are in the range -7‰ to -10‰ and -8‰ to -10‰, respectively, where the dissolution of feldspar constitutes the 1st secondary pore zone. Dolomites (Ⅲ) with wavy extinction have been formed at a burial depth of 3 800-4 000 m, along with the decarboxylation in the methane generating zone, the δ13C is in the range of -11‰ and -16‰, while in the carbonate directly formed from CO2, the δ13C is ±20‰, and the δ18O both in dolomite and carbonate range from -12‰ to -13‰, temperatures measured from secondary SiO2 inclusions are in the range of 110℃ and 120℃. This interval constitutes the 2nd secondary pore zone. The depth interval of 4 500-4 700 m is a wet gas generating zone, the δ13C and δ18O in carbonate (Ⅳ) formed in this interval are in the range of -27‰ to -31‰ and -13‰ to -14‰, respectively, and the temperature measured from inclusion thermometry is 130 -140℃; and the massive dissolution of ferroan calcite has resulted in the formation of the 3rd secondary pore zone. Large amount of dry gas (Ⅴ) were generated at a burial depth of over 5 000 m, where the 8 C ranges from -18‰ to -20‰ and δ18O ranges from -13‰% to -14‰, being accordant with the inclusion's homogenization temperature of 150-155℃. This interval constitutes the 4 th secondary pore zone with porosity in the range of 15% to 20%. The folded strata might have been inverted during Hercynian movement, uplifted and eroded about 5 000 m and associated with'retrodiagenesis'.

Key words: homogenization temperature of inclusion, secondary pore zone, isotope, generation, carbonate cement, Ordovician-Silurian, northwestern Tarim basin

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