Evaluation of Oil Shale Resources in Luozigou, Jilin Province

Luozigou oil shale mining area is located 3 kilometers west of Luozigou Town, Wangqing County, Jilin Province, and 40 kilometers northeast of Wangqing County. Its geographical coordinates are13010' 30 "~13023' 00" and 43 38' ~ 43 50' north latitude. Luozigou basin is located at the eastern foot of Laoyeling in the northern section of Changbai Mountain, and the oil shale-bearing mining area is located in the north-central part of Luozigou basin, which belongs to hilly terrain.

I. Geological background

This area is located in the Luozigou basin of Yanbian syncline in the Yanbian geosyncline fold belt of Jihei fold system, with frequent magmatic intrusion and developed faults.

Structural characteristics of (1)

1. Tectonic background

The regional structure in this area belongs to the northern end of the Liangjiang-Antu northeast structural belt, and the basin is generally controlled by the northeast structure. The northeast structure and the early northwest structure jointly controlled the formation of the basin.

There are mainly three groups of fault structures in this area, namely, NE-trending, NS-trending and NW-trending faults. The Mesozoic basins of Dalazi Formation of Lower Cretaceous are generally distributed in the north-south direction, and a wide and gentle syncline in the NW direction is formed under the influence of NE-directional horizontal compression structure. The oil shale deposit in this area is controlled by the southwest wing of syncline and occurs in the upper sandstone shale section of Dalazi Formation of Lower Cretaceous in Luozigou Basin. In the early stage of basin formation, tectonic volcanic activity was strong, forming basement volcanic lava and clastic rock deposits. In the late stage, volcanic activity stopped and normal clastic rock deposition was formed. The lake water in the basin is relatively stable and a large number of organisms multiply, which creates a favorable geological environment for the formation of oil shale deposits in this area.

2. Geology of mining area

* * * There are four faults in the mining area, namely F 1, F2, F3 and F4, in which F 1 is Xiaonangou fault, F2 is Lvda Yangzigou fault, F3 is Laomuhe fault and F4 is Sandaohe fault. Xiaonangou fault and Lvda Yangzigou fault are small in scale and distributed on the east and west sides of the deposit. Their fault planes are inclined to the west (F 1) and to the east (F2) respectively, and the fault distance is about 10m, which has little influence on ore bodies (layers). Sandaohe fault is located in the south of the deposit. Although the fault has a certain scale, it tends to the southwest, so it has no obvious damage to the deposit. Laomuhe fault is the largest fault in the mining area, and its dip angle and fault distance are still unknown. However, the fault is more than 600 meters away from the mining area boundary. In addition, according to the borehole data of CK4, CK23 and CK24 on the north side of the mining area, the cores seen are relatively complete, and there is no obvious crushing phenomenon, indicating that the fault has little influence on the deposit.

(2) Stratigraphic characteristics

The strata exposed in this area mainly include sandstone shale and conglomerate of Cretaceous Dalazi Formation in Mesozoic, volcanic lava and clastic rock of Quanshuicun Formation, and shallow metamorphic rock series of Permian Kedao Formation in Paleozoic.

The strata in the mining area are sandstone shale section and conglomerate section of the Lower Cretaceous Dalazi Formation in Mesozoic, and the glutenite section is only distributed in the northeast corner of the mining area, and the sandstone shale section is widely distributed. The ore-bearing stratum is the sandstone shale section in the upper part of Lower Cretaceous, which generally strikes northwest and northeast, and the dip angle is about 4 ~ 6, which is a simple monoclinal stratum.

The main lithology is fine sandstone, siltstone, sandy shale, argillaceous shale and oil shale. Only a small amount of medium-coarse grained sandstone and gravelly sandstone were found at the edge of the mining area. According to the sedimentary characteristics of rocks, the change of lithofacies and the general folding phenomenon of shale and oil shale, the sedimentary rocks in this basin were formed in a slightly turbulent environment. According to the ground and borehole data, it is divided into 39 lithologic layers from bottom to top.

(3) Magmatic rocks

Magmatic rocks in this area mainly include Hercynian intrusive rocks and Yanshanian intrusive rocks.

1. Hercynian intrusive rocks (γ34)

Widely distributed around the basin, with an area of about 62.50km2, it is composed of plagiogranite, porphyry granite, granodiorite, quartz diorite and granite.

2. Yanshanian intrusive rocks (γ25)

Mainly distributed in the south of the basin, with an area of about 30km2. Sporadic distribution in the form of small rock, mainly composed of granite, potash granite and adamellite.

Second, the characteristics of oil shale

(A) the physical characteristics of oil shale

The oil shale in this area is black-gray-black, with brown stripes, massive structure, less flaky, greasy, tough and not easy to break, and the fracture surface is shell-shaped or serrated. If it is fried with a knife, it can be ignited with an open flame, releasing thick smoke with a strong asphalt smell.

(2) Technical characteristics of oil shale

The oil content of oil shale is 3.5 1% ~ 14.37%, with an average of 6.72%. The second and third oil shale layers are the main oil shale layers in this area, with good quality, stable occurrence and large resource reserves, which are representative (the oil content in this sampling test is 9.46% ~ 1 1.44%). The calorific value is 20.35MJ/kg, the ash content is 76.39%, the moisture content 1.07% and the total sulfur content is 0.55%.

(III) Types and geochemical properties of oil shale

Oil shale in this area has typical genetic characteristics of inland lakes, and primary sedimentary structures of ore-bearing rock series are developed. It is mainly horizontal bedding, oblique bedding and underwater syngenetic sliding structure (fold structure). Sandy shale, argillaceous shale and oil shale layers in ore-bearing series generally contain a large number of plant debris, fish and petabranchial fossils, indicating that the organic components in oil shale in this area are mixed accumulation of animals and plants. The organic genetic types of Luozigou oil shale belong to sapropelic type (type I) and humic sapropelic type (type II 1) through the determination of chemical elements in organic matter and H/C atomic ratio and O/C atomic ratio of oil shale (Table 5-5).

Table 5-5 Characteristics of Organic Elements in Luozigou Oil Shale

Iii. Mineralization and distribution of oil shale

(A) the occurrence characteristics of oil shale

1. Strata characteristics

Luozigou oil shale is mainly developed in the second member of Dalazi Formation of Lower Cretaceous, with the general strike of northwest and northeast, and the dip angle is about 4 ~ 6, which is a simple monocline. The main lithology is fine sandstone, siltstone, sandy shale, argillaceous shale and oil shale. Only a small amount of medium-coarse grained sandstone and gravelly sandstone are found at the edge of the ore-bearing area. According to the ground and borehole data, 39 lithologic layers are divided from bottom to top.

2. Occurrence characteristics of oil shale

The oil shale in this area occurs in the second member of Dalazi Formation of Lower Cretaceous, with shallow burial (0 ~ 333 m) and gentle dip angle (4 ~ 6). According to the outcrop and engineering control in the mining area, it is known that there are 29 layers of oil shale in * * *. Among them, the second and third layers of oil shale are layered, continuous and stable, with high oil content and large resource reserves, which are the main oil shale layers in this area (Figure 5-5 and Figure 5-6), while other layers are layered or lenticular, with relatively poor continuity and stability (Figure 5-7). From bottom to top, the lithology gradually changes into carbonaceous shale mixed with sandy shale-fine sand shale mixed with oil shale-oil shale mixed with oily sandy shale-oil shale.

Figure 5-5 Isogram of the thickness of the second oil shale in Luozigou oil shale mining area

Figure 5-6 Isogram of Oil Shale Thickness of the Third Layer in Oil Shale-bearing Mining Area

Figure 5-7 Comparison of Main Oil Shale Layers in Luozigou Oil Shale Mining Area

(2) Formation environment of oil shale

1. Tectonic background

In the early stage of basin formation, volcanic activity was strong, forming volcanic lava and its clastic rocks; In the late stage, volcanic activity stopped and the tectonic environment was stable, forming a set of normal sedimentary rocks. Under the control of crustal movement, the bottom of the lake keeps falling and accepting deposition. Affected by the pressure of overlying strata and the temperature caused by geothermal factors, asphalt accumulated in situ to form oil shale deposits through physical and chemical actions such as diagenesis and volatile dispersion. At the same time of mineralization, due to the local tremor of the earth's crust, the seam and surrounding rock strata slide locally, resulting in fold structure, and then descend to accept deposition. The whole sedimentary and metallogenic process is carried out in turbulent environment.

2. Sedimentary environment

During the Dalazi Formation of Lower Cretaceous, the lakes were relatively stable and the natural ecological conditions were good, which was extremely beneficial to the mass reproduction of organisms. Rich organic matter, argillaceous and silty substances are deposited at the bottom of the lake basin, which creates favorable conditions for the formation of oil shale deposits in this area.

At the same time, the oil shale layer contains silty components and has obvious contemporaneous fold structure. This stratum is closely related to sandy shale, and there is almost no clayey rock on its top and bottom plates. Therefore, it is considered that the organic matter of this rock layer is accumulated in the reducing environment of deep water and stagnant water surface. Under the transformation of anaerobic bacteria and the infiltration of a large amount of sediment and silt, humification with more minerals was formed, which created a good foundation for the formation of oil shale.

(3) Distribution characteristics of oil shale

The plane distribution characteristics of 1. oil shale

From the contour map of oil shale layer thickness in Luozigou oil shale mining area (Figure 5-8), it can be seen that the ore-rich centers are near holes CK26, CK30, CK35 and CK40, which are distributed in east-west belts. The maximum thickness of the ore-rich center can reach 20.00m, the minimum thickness can reach 5.00m, the average thickness is 10.25m, and the average oil content is 7.29%. In addition, thick oil shale is also distributed near holes CK 13, CK 19, CK29 and CK39, with an average thickness of 10.00 ~ 15.00 m and an average oil content of 6.1/kloc-0.

2. Vertical distribution characteristics of oil shale

According to the outcrop and engineering control in the ore-bearing area, there are 29 oil shale layers, of which the second and third layers are layered, continuous and stable, with high oil content and large resource reserves, and the rest are layered or lenticular, with relatively poor continuity and stability (Table 5-6).

Figure 5-8 Isogram of Oil Shale Thickness in Luozigou Oil Shale Mining Area

Table 5-6 Occurrence Characteristics of Luozigou Oil Shale Orebody

sequential

Four. Evaluation of oil shale resources

(1) Analysis of the degree of exploration work

1. Geological exploration work

During the period of 1933 ~ 1939, the Japanese successively conducted many geological surveys on local surface outcrops and shallow ore bodies of oil shale ore in Luozigou basin, and conducted trench exploration, well drilling and drilling in some areas, and made a detailed study on the physical and chemical properties of oil shale ore. Through sampling analysis, the highest oil content of oil shale ore in the mining area is 14.438+04.

During the period of 1955 ~ 1957, the Northeast Geological Bureau 134 team made a general survey and detailed investigation of the Luozigou oil shale mining area, and confirmed that there were 6 layers of exploitable oil shale deposits with industrial significance in the mining area, and the oil shale ore resources were proved to be1900,000 t.

From 2002 to 2003, the sixth geological survey in Jilin Province strengthened the comprehensive research work on the basis of the previous geological work, systematically sorted out and summarized the existing geological data, and carried out supplementary exploration work in the mining area in view of the main problems existing in the original report, basically identified 7 layers of industrial recoverable oil shale deposits in the mining area, estimated the economic resources of oil shale ore to be 6.5438+0.4752 million t, and submitted Luozi County, Jilin Province.

2. Degree and accuracy of exploration

(1) exploration degree and grid.

The Supplementary Detailed Investigation Report of Oil Shale Mine in Luozigou Mining Area, Wangqing County, Jilin Province pointed out that according to the comprehensive analysis of oil shale beds and industrial orebodies controlled by surface trench well exploration and deep drilling engineering in the mining area, and referring to the relevant requirements of Code for Coal Geological Exploration, Luozigou oil shale deposit should be of moderate structural complexity, and the stability of oil shale coal seam belongs to a relatively stable type, that is, submit a 500m×500m engineering network to verify the pre-feasibility economic basic reserves. 1000m× 1000m project grid is submitted to control the economic base reserves, and 1000m×2000m project grid is submitted to speculate the internal economic resources.

(2) Exploration accuracy.

According to the statistics of exploration area, construction boreholes, exploration lines and grids, the statistical results of oil shale reserves at all levels show that the exploration area of Luozigou oil shale deposit is 19.22km2, with 53 boreholes and 3 boreholes /km2, and the borehole density is relatively high. According to the statistical results of core recovery rate of construction drilling, the core recovery rate is ≥65%. More than 95% of the coal seams and surrounding rocks near the mine have a recovery rate of ≥85%, and the recovery rate of core drilling is high, which can meet the requirements of detailed investigation and resource reserve estimation. * * * There are 12 exploration lines in the mining area, and the spacing between trenches and wells is 500 ~1000 m.. Trenches and wells in the area are all dug to 0.5m below bedrock, ensuring the bottom width of 0.8 ~ 1.00m, meeting the requirements of geological sampling and cataloging, and the utilization rate of trench exploration is 100%.

(2) Resource evaluation

1. Resource evaluation

The evaluation results show that the proven resource reserve of Luozigou oil shale mining area is 230.9 million t, and the recoverable resource reserve of oil shale identification technology is148.64 million t; The proven reserves of shale oil are15.04 million t, the recoverable reserves of shale oil identification technology are 97 1 10,000 t, and the recoverable reserves of shale oil are 7.28 million t. ..

2. Resource forecast

The prediction is divided into three prediction areas: the eastern, southern and lower parts of the exploration area. The thickness of oil shale in the east and south is 34.96m, and the oil content is 6.5 1%. The thickness of oil shale in the lower part is1kloc-0/(borehole ZK). Borehole ZK 10 1 contains 4.95% oil, and the weight of the analog exploration area is 1.94t/m3. The boundary of the eastern prediction area is controlled by exploration areas F5, F2 and F6, the boundary of the southern prediction area is controlled by the upper stratum boundary of F5 and Dalazi Formation, and the boundary of the lower prediction area is controlled by F6 and Dala. Multiplied by the area effective coefficient (oil shale occurrence area/exploration area), the oil shale areas are 2.55km2, 5.32km2, 1 1.27km2 respectively. * * The potential oil shale resources are 860.36 million tons, and the potential technically recoverable oil shale resources are 301130 million tons; The potential resources of shale oil are 509 10000 t, the potential technically recoverable resources of shale oil are 1782 t, and the potential recoverable resources of shale oil are 1336 t.

In this evaluation, the reserves of oil shale in Luozigou oil shale mining area are1091270,000 t, and the reserves of oil shale technically recoverable resources are 449.77 million t: 65.95 million tons, 27.53 million tons and 20.65 million tons.

Table 5-7 Oil shale and shale oil reserves in oil shale-bearing mining areas