Full
ZHOU Lingfang,born in 1969,senior engineer,is engaged in research on carbonate sedimentary and reservoir evaluation. E-mail: jzzlf309@21cn.com.
Outline
The diagenetic sequence and pore evolution of ancient carbonate rocks in deep or ultra-deep burial depth is one of the hot topical in reservoir evolution. Based on analysis of the petrographic, geochemical, and U-Pb dating of diagenesis minerals of the Dengying Formation at Chuanshen 1(CS1), Jinshi 1(JS1) and other wells, the authors has adopted the comparative methods, in which compare the matrix dolomites with different dolomite cements, as well as the other diagenetic minerals, occurred in cement or fillings in vugs & fractures with regard to the data of carbon, oxygen, and strontium isotopes, homogenization temperatures, U-Pb dating of dolomites and calcites, either in the Dengying Formation of Ediacaran, or Xianrendong Formation of the Early Cambrian, or Maokou Formation of Middle Permian. The diagenetic sequence has been reasonable modified: fibrous or fibrous growth→column fibrous or foliated or blade(length-fast cement) or dogtooth shaped→coarser fibrous or bundle shaped of marine cementation and bundle shaped cement or fasicular or radial dolomite cements. i.s botryoids or comb shell shaped or primary dolomite biomorphs of nanoscale spheroids→micro-stalactitic or vadose silt of meteoric cementation→cryptocrystalline or microcrystalline quartz(1st)→fluorapatite, barite and fluorite(1st)→semi-automorphic micro-crystalline dolomite→fine crystalline dolomite→fine and medium crystalline quartz(2nd) or medium to coarse dolomite→Saddle dolomite(1st)→medium to coarse crystalline calcite(1st)→hydrocarbon discharge(episodes)→fluorite(continuous dissolution. 2nd or 3rd)+coarse calcite(2nd)→coarse quartz(3rd)+Galena+Sphalerite+Pyrite+Fluorite(4th)+coarse calcite(3rd)+coarse crystalline dolomite(or Saddle dolomite(2nd)→pyrobitumens(pyrolysis or TSR, methane)→coarse calcite(4th)+quartz(4th); and the medium to coarse dolomite in some of the fractures or cavities is of early hot fluid dolomite origin, with relatively low ${\delta }^{13}{\mathrm{C}}_{\mathrm{P}\mathrm{D}\mathrm{B}}$(-1.78‰~-1.69‰) and ${\delta }^{18}{\mathrm{O}}_{\mathrm{P}\mathrm{D}\mathrm{B}}$(-9.28‰~-9.32‰) and moderate. homogenization temperatures(Th=130.9 ℃, 135.3 ℃, 116.6 ℃) and salinity(12.63wt% NaCl); the U-Pb Concordia Age of dolomite(DⅡ-Ⅲ)is between 474.0±74.0 Ma to 482.0±56.0 Ma, By integrating analyses of burial history, the geological-time of dolomite(DⅡ-Ⅲ) is mostly like to occur in the late Ediacaran to Cambrian(No later than Early Ordovician). The weak extension during the late Ediacaran to Cambrian period, interval by multiple episodes of tectonic compression and exhumation, provided the conditions for the meteoric water percolated downward along the faults or fractures, heated by deep circulation as well as mixing with formation water, lead to precipitate of dolomite. The diagenesis effect on pore evolution display that the early dolomite cementation developed in hot fluid had a smaller proportion and had little effect on pore reduction, in compared with diagenesis such as large-scale marine cementation, strong silicification, compaction, and dedolomitization.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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