SY/T 5477-1992 Specification for classification of diagenetic stages of clastic rocks
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Petroleum and Natural Gas Industry Standard of the People's Republic of China SY/T 5477--92
Specification for the Division of Diagenetic Stages of Clastic Rocks
Published on September 17, 1992
Ministry of Energy of the People's Republic of China
Implementation on February 1, 1993
1 Subject Content and Scope of Application
Petroleum and Natural Gas Industry Standard of the People's Republic of China Specification for the Division of Diagenetic Stages of Clastic Rocks
This standard specifies the division, naming, basis, symbols and methods of diagenetic stages of clastic rocks. This standard is applicable to the division and characteristic research of clastic rock province stages. 2 Basis for the Division of Diagenetic Stages
2.1 Distribution and formation sequence of authigenic minerals and homogenization temperature of inclusion bodies in authigenic minerals. SY/T 547792
2.2 Clay mineral assemblage and transformation of illite/montmorillonite (1/S) mixed-layer clay minerals (refer to Reynolds's X-ray radiographic chart of illite/montmorillonite (1/S) mixed-layer clay minerals, calculated using the V/P method) See Appendix A (reference) 2. Structure, structural characteristics and pore types of rocks. 2.4 Organic matter maturity.
2.5 Paleotemperature.
2.5.1 Fluid inclusion homogenization temperature.
2.5.2 Authigenic mineral formation temperature.
2.5.3 Evolution of I/S mixed-layer clay minerals. 3 Signs of each diagenetic stage
Characteristics of petrology, temperature, and organic matter maturity in different diagenetic stages Table 1.1 Syngenetic stage and main signs
The period of changes and actions that occurred after sediment accumulation and before burial is called the syngenetic stage. Its main signs are as follows. a. Beach chlorite is mainly formed in this stage
b. Formation of chlorite:
C. Formation of syn-nodules
d. Microcrystalline and patchy mud products siderite distributed along the bedding plane e. Micritic borate distributed between grains and grain surfaces, sometimes with fibrous and micro-particle calcite, f. Sometimes with crescent and gravity cementation.
3.2 Early and late diagenetic stages and main signs The diagenetic stage refers to the period of physical and chemical actions that occurred when the sediment package was separated from the water body at the time of deposition and was cemented and consolidated during the storage process until metamorphism.
3.2.1 Early diagenetic stage
It refers to the stage from weak lying to consolidation of sediments, which can be divided into two stages, A and B. 3.2.1.1 Diagenetic stage A
a. The paleotemperature range is room temperature ~ 65℃
b. The organic matter is immature, its vitrinite reflectance (R.) <0.35%, the color of spores and pollen is light yellow, and the thermal change index (T.AI) <2.0s Approved by the Ministry of Resources of the People's Republic of China on September 17, 1992 and implemented on February 1, 1993
SY/T 5477-92
c. The rock is weakly consolidated and half consolidated, with developed primary intergranular pores. Generally, no quartz is found, and feldspar is less dissolved. Early carbonate knots (fibrous, comb-like, and microgranular) and marginal mudstone rings can be seen.
6. In mudstone, there is smectite, and there are also disordered mixed-layer new minerals (order R=0) with smectite layers accounting for more than 70% of the 1/S mixed layer, collectively known as montmorillonite
f. Smectite, disordered mixed-layer minerals and a small amount of authigenic kaolinite can be seen in sandstone. 3.2.1.2 Grass diagenesis B period
a, the paleotemperature range is >65~B5℃
b. The organic matter is in the semi-mature stage, the vitrinite reflectance (R.) is 0.35%~0.5%, the spore pollen color is yellow, and the thermal change index (T41) 2.0-~2.5t
c, due to compaction and cementation of sulfonates and sulfates, the rock is semi-consolidated to consolidated. Primary pores can be preserved, and a small amount of secondary pores can be seen
d In mudstone, montmorillonite is a mixed clay mineral transformation of smectite/montmorillonite (I/S), and the montmorillonite layer accounts for 70%--50%, which is a disordered layer (ordered degree 0), called disordered mud layer zone, e: Some sandstones still contain montmorillonite, and leaf-shaped white kaolinite is more commonf. It can be seen that the "grade quartz type" is added, with enlarged edges or white-shaped surfaces. Under the scanning electron microscope, small quartz crystals can be seen, which are single or connected into irregular crystals:
9: In some sandstone matrixes, there are cloud-like monsoons, and some mineral replacement and transformation phenomena can be seen (mica-chlorite). 3.2.2 Late diagenetic stage
refers to the stage after the rock is consolidated, in a deep buried environment until metamorphism. It is divided into A, B, and C stages. 3.2.2.1 Late diagenetic stage
a, the ancient range is >85140℃
b. The organic matter is mature, and the vitrinite reflectance (R.)>0.5%1.3%. The sporopollen color is yellow-brown, and the thermal change index (TAI)>2.5~3.71
C. Late iron-carbon salt cement can be seen , especially iron dolomite, which is often powdery to fine crystals, appears in the form of replacement, enlargement or cementation.
d The feldspar and other clastic particles and carbonate belts are dissolved, and some of them have dissolution residues, and secondary pores are developed! e, Quartz secondary addition belongs to level II, most of the quartz and some feldspar have secondary enlargement, and the euhedral crystal faces are developed, and some quartz microstructures are seen. Under the scanning electron microscope, the surface of most particles is wrapped by relatively complete euhedral surfaces, and some white crystals grow into the pore space, staggered and connected, blocking the pores;
f: Clay minerals in sandstone, including authigenic kaolinite and chlorite/montmorillonite (I/) mixed-layer clay minerals, a large amount of whisker-shaped authigenic euhedrite and blade-shaped, flocculent white chlorite, and sometimes other authigenic minerals such as sodium euhedral, monozeolite, chlorite/montmorillonite (C/S) mixed-layer clay minerals can be seen.
9. The illite/montmorillonite (1/S) mixed-layer clay minerals in mudstones, montmorillonite layers account for 50% to >15%, of which <50% to >35% are partially ordered mixed layers (H=0/R=1, 35% to >15% are ordered mixed layers (R=1). In some strata with igneous rock intrusions or rocks rich in volcanic fragments and in salt lake water medium basins, the transformation and distribution of montmorillonite and illite/montmorillonite (I/S) mixed-layer clay minerals are sometimes abnormal, and other indicators should be combined to divide the diagenetic stages. In the late diagenetic A period, according to the evolution of illite/montmorillonite (1/S) mixed-layer clay materials, it can be further divided into two sub-periods, A and A2, with the montmorillonite layer convexity of 35% or the vitrinite reflectance (R.) of 0.7% as the boundary. 3.2.2.2 Late diagenetic stage
a, paleotemperature range is ≥140~170℃
b. Organic matter is in a high maturity stage, vitrinite reflectance (R.) is>1.3%2.0%, pollen color is brown-black, TAI is 2
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SY/T 5477—92
c. The secondary enlargement of quartz in sandstone is subgrade. Almost all quartz and feldspar under thin section have enlarged and wide edges, mostly inlaid. d. Under scanning electron microscope, quartz white crystals between particles are interconnected, the rock is relatively dense, and cracks are developed; e. Some contain iron carbonate minerals, kaolinite is significantly reduced or absent, and some can be seen with lauzenite and albite. f. There are illite and illite/montmorillonite (1/S) mixed-layer clay minerals in mudstone, and the montmorillonite layer is ≤15%, which is a superlattice ordered mixed layer (order degree is 3), collectively known as superlattice ordered mixed layer zone. 3.2.2.3 Late Formation C Period
a. Paleotemperature range>170~~200°0
b. Organic matter is in the overmature stage, vitrinite reflectance (R.)>2.0%~4.0%, sporophyte is the color of illumination c. The rock is extremely dense, with very few pores and developed cracks. Late carbonate minerals and authigenic minerals such as albite and sphaerocite can be seen in sandstones
d. Quartz enlargement belongs to Grade II, the grains are sutured, and the white crystal surface disappears e. The grains are in suture contact and suture lines appear: f. The representative clay minerals in sandstone and mudstone are illite and chlorite, and there are shovel mica and sphaerocite mica. The mixed layer has disappeared, which is called illite-chlorite.
3.2.3 Epigenetic stage
refers to weakly consolidated or consolidated clastic rocks in a certain diagenetic stage, which are exposed or close to the surface due to tectonic uplift, and are eroded by fresh water, and undergo changes and destruction.
a. The phenomenon of low-valent iron-containing minerals (such as pyrite, hemp iron, etc.) being impregnated with limonite or halo limonite b. Oxide film on the surface of clastic particles;
C: crescent-shaped carbonate cementation and gravity cementation d, seepage filling s
e. Epigenetic calcareous nodules!
f. Gypsumization of anhydrite,
g. Epigenetic kaolinite"
h, dissolution phenomenon.
SY/T 5477—92
Radiograph A
Calculation method of illite/montmorillonite mixed layer ratio
(reference)
A1For disordered and partially ordered illite/montmorillonite mixed layers, use the V/P method. A1.1
So=66.V/P+39.
Where: S. —The initial value of the proportion of montmorillonite layer in the illite/montmorillonite mixed layer, %, V
—The distance from the top of 17A peak to the valley of 17A peak, mm3(A1)
P—The distance from the top of 17A peak to the bottom line, mm1The bottom line is a straight line passing through the minimum background point and parallel to the 20 coordinate axis.
(i=1, 2, 3)
where s
is the proportion of smectite layer in illite/smectite mixed layer, and Ci
is the correction coefficient related to the content of illite/smectite mixed layer. 01=1.888-0.19521mX
Q2-1.633-0.141nX75S.50
(=1.129-0.0013X50>Sa37
A2For ordered mixed layers, the determination of the mixed layer ratio S is shown in Table A1. Table 29 is the angle of incidence of the mud layer peak, in degrees (°). Table A1 Data table for calculating the ordered illite/montmorillonite mixed layer ratio s.%
28, ()
Additional notes:
This standard was proposed by the Petroleum Industry Standardization Technical Committee. 25
This standard is under the technical management of the Petroleum Geological Exploration Professional Standardization Committee. This standard was drafted by the Experimental Center of Beijing Petroleum Exploration and Development Research Institute. The drafter of this standard is Ying Fengxiang.
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