I. Geological background
Structural characteristics of (1)
This area is located in the red fault basin on the east side of Maotai fault, and the south wing of the secondary uplift in the north wing of Huaxia Changdanghu composite syncline is hidden under it. The wing is composed of basement and two sets of caprock structures, and the structural style of overlapping of coal measure uplift belt and Cretaceous and Paleogene subsidence belt is described as follows:
1. caprock structure
From the analysis of regional structure, this area rose after the Middle Triassic and suffered from erosion for a long time, so the Carboniferous-Middle and Lower Triassic strata suffered from different degrees of erosion, and it was not until the Late Cretaceous that a set of thick red clastic deposits was deposited, which became the first set of caprocks, forming an asymmetric sedimentary basin with an axial direction of 54 north and south. At the end of Mesozoic, it experienced another uplift and denudation, and deposited Paleogene strata, forming a 62-east deposit in the basin, which overlapped with the sandstone of Chishan Formation.
2. Basement structure
The basement is a short-axis anticline, and the core of the Gulongshan-Tushan short-axis anticline is composed of Devonian Wu Tong Formation and Lower Permian Qixia Formation, with an axial direction of 60 from east to west, and the stratigraphic strike turns to the northwest with an inclination of about 40, and the two wings are covered by two sets of caprocks.
(2) Stratigraphic characteristics
The bedrock in this area is covered by Quaternary, and the Permian, Triassic, Cretaceous, Paleogene and Quaternary are all exposed by drilling. Now the new and old strata are described as follows:
(1) Lower Permian:
① Qixia Formation: The main lithology is gray-dark gray limestone with medium thickness, compactness and medium hardness.
② Gufeng Formation: The middle and upper parts are mainly composed of gray dark gray fine sandstone, siltstone and siltstone interbeds. The lower part is mainly composed of dark gray and gray-black siltstone, mudstone and siliceous mudstone.
(2) Upper Permian:
① Longtan Formation: The upper part is mainly gray and dark gray fine sandstone, siltstone and mudstone. The coal-bearing section is mainly composed of gray, grayish white, dark gray and grayish black medium-fine grained sandstone, siltstone, mudstone and coal seam.
② Dalong Formation: mainly grayish black, deep stucco rock, siliceous mudstone, thin siltstone and limestone.
(3) Middle and Lower Triassic Qinglong Group: grayish white-fleshy red limestone, thin-medium-thick layered gravelly limestone with angle at the bottom, purplish red, grayish green and gray mudstone.
(4) Cretaceous Chishan Formation: brick red siltstone, siltstone and fine sandstone. The bottom is mainly thick conglomerate.
(5) Paleogene: The lithology is mainly gray-green mudstone, gray mudstone and siltstone.
(6) Quaternary: mainly yellowish brown, brown clay and sandy clay.
Second, the characteristics and distribution characteristics of oil shale
(A) Analysis of oil shale characteristics
The main feature is that the nails are black, blocky, delicate, slightly light, dull and soft. The average ash content can reach 80.80%, the rock composition is mainly inorganic, the ash composition is mainly high-content SiO2 _ 2 and CaO, the organic matter contains 0 ~ 10.09% asphaltene, and the C/H value is 3.65 ~ 9.03. The oil content is low, averaging 4.82%, and the calorific value is low, averaging 2.2MJ/kg.
(2) Environmental analysis of oil shale formation.
The oil shale interval in this area was formed in a relatively calm and deeply covered reducing environment. It is a solid combustible organic rock transformed from the remains of lower plants such as algae and a small number of aquatic animals, belonging to saline-semi-saline lake facies deposition.
(3) Distribution characteristics of oil shale
The distribution of oil shale in this area is controlled by Paleogene sedimentary depressions and related to Mesozoic and Paleozoic concealed anticlines. Located in a small depression on the southeast edge of Zhixiqiao sag, it is distributed in a horseshoe-shaped belt with northeast opening around the axis of Tushan concealed anticline. Its southwest extension may disappear in a dustpan shape, and its northwest disappears in the direction of Maoshan, with a tendency of NW3-20, with an average of less than 10. It is mainly divided into 1 layer and is a lacustrine product. Coal seam thickness 1.59m, coal seam area 0.86km2, coal seam dip angle less than 10, buried depth 26 ~ 190 m, coal seam weight 2.09t/m3, oil content 4.82% (.
Figure 6- 12 Isograms of Oil Shale Thickness (a) and Oil Content (b) in Shanxi Oil Shale Area of Jintan
Three. Evaluation of oil shale resources
(1) Analysis of the degree of exploration work
1. Geological exploration work
This area was explored by No.5 Team of Jiangsu Coalfield Geological Exploration in June 1984 1 1, and the report was submitted. The exploration degree has reached the requirements of the exploration stage.
2. Degree and accuracy of exploration
Through exploration, there are 4.53 million tons of B+C+D reserves in Ⅱ 2, Ⅱ1coal seam and above 600m elevation, of which B reserves1130,000 tons, accounting for 25% of the total reserves, and B+C reserves are 4.2 million tons, accounting for 93% of the total reserves. In addition, the prospective reserves of ⅱ 2, ⅱ 1 and ⅲ 2 coal seams are 3.22 million tons, with a total reserve of 7.75 million tons, and 74 boreholes have been used, with the number of boreholes per square kilometer 16.
(2) Resource evaluation
1. Resource evaluation
The results of resource evaluation show that the oil shale resource reserves in the mining area are 2.85 million tons, the proven resource reserves are 2.85 million tons and the technically recoverable resource reserves are 2 million tons. It is found that the reserves of technically recoverable resources are 2 million tons. The shale oil reserves are 6.5438+400,000 tons, the proven reserves are 6.5438+400,000 tons, and the technically recoverable reserves are 6.5438+400,000 tons. The proven technically recoverable resources reserves are more than 654.38 million tons. Reserves of recoverable resources are 80,000 tons.
2. Resource forecast
The oil shale in this prediction area occurs in the Eocene Funing Formation, mainly in 1 layer, which is a lacustrine product. The dip angle of coal seam is less than 10, and the buried depth is 26 ~190 m. According to the geological characteristics of Tushan exploration area and the comprehensive analysis of regional geological data, it is predicted that the oil shale is formed in lacustrine facies. The humid climate during the metallogenic period is beneficial to the development of oil shale. On this basis, the development characteristics of Eocene Funing Formation in Tushan mining area are compared, and the oil shale resources in the west of Tushan are predicted.
During the prediction, the thickness, oil content and specific gravity of the prediction area are obtained according to the layering, thickness, oil content and specific gravity of oil shale in the known exploration area and the thickness, oil content and weight of wells outside the known exploration area. The thickness of coal seam is 2.63m, the oil content is 4.24%, and the weight of coal seam is 2.09t/m3. By comparing the effective distribution area of oil shale in the prediction area with the known exploration areas, the classification coefficient is 0.38, the distribution area of oil shale strata in the prediction area is 15.99km2 multiplied by the analogy coefficient, and the effective distribution area of oil shale in the prediction area is 6.08km2 Then, the oil shale resource reserves are calculated by the volumetric method. The calculation results show that the potential resource of oil shale is 33.4 million tons. The potential technical recoverable resources are165438+690,000 t, the potential shale oil resources are 14 1 10,000 t, the potential technical recoverable resources are 500,000 t and the potential recoverable resources are 380,000 t.
According to the comprehensive analysis of the above two areas, the resources of Tu Shan oil shale mining area in Jintan are comprehensively evaluated. The results of resource evaluation show that the oil shale resources in this mining area are 36.25 million tons, including 2.85 million tons of proven resources, 33.4 million tons of potential resources, 6.5438+0369 million tons of oil shale technical recoverable resources, 2 million tons of proven technical recoverable resources, 654.38+065.438+069 million tons of potential technical recoverable resources and 6.5438 million tons of shale oil. Among them, the proven technically recoverable resources are more than 654.38 million tons, and the potential technically recoverable resources are 500,000 tons ... The shale oil recoverable resources are 460,000 tons, the proven 80,000 tons and the potential recoverable resources are 380,000 tons. ..