Effect of Hydrocarbon Emplacement on Diagenesis of Silurian Sandstone of Central Tarim Basin
-
摘要: 塔中地区志留系具有较广的沥青分布,为研究烃类侵位对矿物成岩作用的影响提供了良好的实例。通过岩矿观察,并综合油田水化学、氢氧锶同位素和流体包裹体均一化温度等资料,提出该区志留系烃类侵位后因淡水注入而使烃类被氧化,所产生的有机酸促进了钾长石、石英等矿物的溶解,导致了次生孔隙的发育;并为石英次生加大提供所必需的Si的来源。Si的质量转移可能是因浓度梯度而引起的扩散作用进行的。烃类侵位还使成岩介质还原性增强,使得胶结物富含还原的 2价铁;但未能阻滞石英的次生加大.Abstract: Silurian bitumen-hearing sandstoncs in Central Tarim are shown to he a good case to study influence of hvdrocarhon emplacement on diagcncsis.We have carried it out by means of observation of thin sections, SEM of sandstoncs in congwnction with analysis of water chemistry, organic acid anions and δD,δ18O,87Sr/86Sr of oilficld water and homogenization tcmpcraturcs of fluid inclusions of the sandstoncs. It can he found that quartz secondary overgrowth coexists with reservoir bitumen.Bitumen may occur between quartz overgrowth and grains in coarser sandstoncs or occlude in the centre of pore in finer sandstoncs.Homogenization temperaturcs of organic inclusions are divided into 2 groups: 59.5-82℃ and 103-125℃,suggestive of at least 2 phases of oil emplacement.The latter is close to the present temperatures of the bore hole hottom, indicating that the late oil and gas cmplacement took place in the late Yanshan to early Himalava Orogcny and quartz overgrowth is not inhibited by oil cmplaccmenu and ccmcntation continucds to present day. Relationships between Br and Ca,Mg,Sr,Cl,CF(CF=Ca+Mg+Sr-SO4-HC03,meq/L) show that oilficld wato is evolved by suhacrial evaporation of scawatcr and subsequent mixing with meteoric water evidenced by relationship between δD and δ18O.Relative enrichment of Ca,Sr,K and depletion of Mg is explained to he a result of dissolution of K- feldspar,dolomitization of calcite and alhitivation of feldspar.87Sr/86Sr of 14 water samples range from 0.710 44 to 0.712 58,much larger than Silurian seawater, indicating that Rh-enriched dctrital minerals such as I}-feldspar, mica and illitc from sandstone or mudstonc contribute significant amount of 87Sr to oilficld waters. It is proposed that organic acids and anions } hydrocarbons he generated by as a result of meteoric water influx after oil emplacement. Organic acids enhance dissolution of minerals such as K-feldspar, quartz leading to generation of secondary porosity and supply additional Si necessary for quartz overgrowth. Si mass transport is through diffusion due to concentration difference as a result of Si precipitation on dctrital quartz.And this is the reason why quartz overgrowth was not inhibited.And Fe II in authigcnic minerals such as Fe-dolomite Fe-calcite and pyrite is mainly derived from reduction of Fe203 due to low Eh resulting from hydrocarbon emplacement. It can he found that bitumen-hearing sandstone is grey, dark grey, even black in comparison with color brown in most non- bitumen-hearing sandstone, suggesting that the former was bleached.~
-
[1] 1 Howseknecht D W.Assessing the relative importance of compaction processes and cementation to reduction of porosity in sandstones[J]. AAPG Bull，1987，71（6）：633 ~ 642
2 Saigal G C，Bj"rlykke K and Larter S. The effects of oil emplacement on diagenetic processes-Examples from the Fulmar reservoir sandstones，Central North Sea[J].AAPG. Bull.,1992，76（7）：1 024 ~ 1 032
3 Nedkvitne T，Karlsen D A，Bj"rlykke K et al. Relationship between reservoir diagenetic evolution and petroleum emplacement in the Ula Field，North Sea[J]. Marine and Petroleum Geology，1993，10：255 ~ 270
4 Bjorlykke K，Aagaard P，Egeberg P K et al.Geochemical constraints from formatiom water analyses from the North Sea and the Gulf Coast Basins on guartz，feldspar and illite precipitation in reservoir rocks[A]. In：Cubitt J M，England W A，eds. The Geochemistry of Reservoirs [C].Geological Society Special Publication，No.86，1994.33 ~ 50
5 王琪，史基安，肖力新等. 石油侵位对碎屑储集岩成岩作用序列的影响及其与孔隙演化的关系—以塔西南石炭系石英砂岩为例[J]. 沉积学报，1998，16（3）：97 ~ 101
6 蔡春芳，梅博文，马亭等. 塔里木盆地不整合面附近成岩改造体系烃—水—岩相互作用[J]. 科学通报，1995，40（24）：1 253 ~ 1 256
7 蔡春芳，梅博文，马亭等. 塔里木盆地流体—岩石相互作用研究[M].北京：地质出版社，1997.1 ~ 155
8 蔡春芳，张敏，徐中一等. 塔里木盆地储层沥青成因探讨[A]. 见：有机地球化学研究进展[C]. 江汉石油学院地球化学研究中心，重庆：重庆大学出版社，1996.14 ~ 20
9 侯会军，王伟华，朱筱敏. 塔里木盆地塔中地区志留系沉积相模式探讨[J]. 沉积学报，1997，15（3）：41 ~ 47
10 肖中尧，张水昌，赵孟军等. 简析塔中斜坡A 井志留系油气藏成藏期[J]. 沉积学报，1997，15（2）：150 ~ 153
11 蔡春芳，梅博文，马亭等. 塔里木盆地油田水的成因和演化[J]. 地质论评，1997，43（6）：650 ~ 657
12 Stueber A L，Purhkar P，Hetherington E A. A strontium isotopic study of formation waters from the Illinois basin，U. S. A[J]. Applied Geochemistry，1987，2：477 ~ 494
13 Faure G. Principles of Isotope Geology（2nd Edn）[M]. New York：Tohn Wiley & Sons，Inc.,1986.1 ~ 589
14 Stueber A，Purhkar P，Hetherington E A. A strontium isotopic study of Smackover brines and associated solids，southern Arkansas [J].Geochimica et Cosmochimica Acta，1984，48，1 637 ~ 1 649
15 Connolly C，Walter L M，Baadsgaad H，et al. 0rigin and evolution of formation waters，Alberta Basin，Western Canada Sedimentary Basin：II. Isotope systematics and water mixing[J].Applied Geochemistry，1990，5：397 ~ 413
16 Knauth L P，Beeunas M A. Isotope geochemistry of fluid inclusions in Permian halite with implications for the isotopic history of ocean water and origin of saline formation waters [J].Geochimica et Cosmochimica Acta，1986，50： 419 ~ 433 -
点击查看大图
计量
- 文章访问数: 570
- HTML全文浏览量: 10
- PDF下载量: 501
- 被引次数: 0
下载:
