Resource evaluation of Huadian oil shale mining area

Huadian oil shale ore-bearing area is located in huadian city, Jilin Province, with an area of about 40km2. Its geographical coordinates are east longitude126 43' ~126 54' and north latitude 42 56' ~ 43 00'. The geographical environment is low mountain and hilly area, with developed water system and complex hydrogeological conditions. The ore-bearing area has convenient transportation and good natural conditions, which is suitable for the exploitation of oil shale deposits.

(1) survey of exploration and development

The exploration of oil shale deposits in Huadian Basin was completed by the Second Geological Exploration Bureau of Northeast Coalfield 1 13, 12 and Jiaohe Coal Mine Exploration Team during the period of 1955 ~ 1959, and a large number of mechanical drilling, manual drilling and trench exploration were completed. Seven reports including Geological Survey Report of Gonglangtou Exploration Area in Huadian Oil Shale Ore Field were submitted. The exploration areas of Gonglangtou, Dachengzi, Miaoling and Beitaizi have reached the exploration level (detailed investigation), and the southern part has reached the prospecting stage. In this evaluation process, a small number of samples were subjected to low-temperature dry distillation, industrial analysis, organic matter type, organic matter abundance and maturity analysis.

1953, No.9 Petroleum Plant in Northeast China was established, and an internal-external parallel heating retort with a height of 100 was built, with an annual output of 5× 104 t of shale oil. 1954, No.9 Petroleum Plant expanded its scale according to the resource situation, designed the annual output of 20× 104t shale oil, and processed it into refined oil. For many years, there has been a local mine (small well) in huadian city. The development and utilization of oil shale is mainly fuel exploitation, and industrial and mining enterprises use oil shale as power fuel. 1993 to 1996 With the joint efforts of the state, provincial and local governments, an oil shale demonstration power plant was established in huadian city, Jilin Province. The overall goal is to achieve an annual oil-consuming shale production capacity of 36× 104t, an annual power generation capacity of 18 000kW/h, an annual power supply capacity of 14 400kW/h, an annual heating capacity of 365,438+one million Ji Jiao, and an annual building materials output of 30× 104m3. In 2003, the National Development and Reform Commission approved the construction of an oil shale production line in Huadian, with an annual output of 25 1× 104t, the installation of two 50,000-kilowatt generator sets, and the comprehensive utilization of building materials. At present, preparations are under way.

(2) Geological characteristics

Huadian oil shale mining area is a faulted basin on Dunmi fault zone. The tectonic framework of the basin is a nearly east-west semi-graben basin with the strike of NE-NEE and the dip angle of 65438+05 ~ 20. The southern margin fault of the basin (F 1) is a basin-controlling synsedimentary margin fault, which controls the Paleogene stratigraphic deposition. Oil shale occurs in Huadian Formation of Paleogene. In the late stage of the basin, faults are the main structural transformation, which can be divided into two groups, one is NW-trending faults (F2, F3), and the other is NE-trending faults (F4, F5). The gentle monoclinic structure is divided into three fault blocks, namely Gonglangtou fault block, Dachengzi fault block and Beitaizi fault block. The basin is mainly filled by Cenozoic Paleogene sedimentary strata, which contain coal, oil shale, oil and natural gas. Huadian oil shale-bearing area was filled by Paleogene Huadian Formation (E2-3h) and deposited as Lower Pyrite Member (E2-3H 1) from bottom to top. The middle oil shale (E2-3h2) is dominated by shallow lake facies, and the sedimentary rocks are gray and dark gray mudstone and oil shale. It contains 8-26 layers of oil shale, 6- 13 layers, and 3-5 layers of thin grayish white fine sandstone, with a section thickness of 50-240m. Upper coal-bearing section (E2-3h3).

(3) Metallogenic conditions of oil shale

1. synsedimentary structure

When the oil shale section was deposited, the basin structure was semi-graben. The contour map of oil shale profile thickness shows that the primary sedimentary thickness increases from the north to the fault side of basin margin, and the sedimentary center is located on the fault side (Gonglangtou-Dachengzi area), with the thickness of 180 ~ 240 m, and the settlement center is consistent with the sedimentary center, which is a syngenetic sedimentary structure. Along the strike of the basin, the sedimentary thickness in the west (Beitaizi area) is thin, only about 50 meters, and thick in the east, about 240 meters.

The controlling effect of synsedimentary structures in the basin on coal and sedimentary minerals is mainly manifested in controlling sedimentary environment and affecting the generation and accumulation of coal-forming materials and other ore-forming materials. The synsedimentary structure in Huadian mining area affects the thickness distribution of oil shale by controlling the accumulation space, and the oil shale is thicker near the basin-controlling fault. The cumulative recoverable thickness of oil shale is 4 ~ 10m in the west and 20 ~ 35m in the east. The position of oil shale rich ore belt is consistent with the sedimentary center, which indicates that synsedimentary faults control the deposition of oil shale deposits. Influenced by synsedimentary structure, Gonglangtou-Dachengzi section is the catchment center of oil shale deposition. The oil shale from layer 13 to layer 9 was originally deposited. At this time, Beitaizi area has not been deposited. With the increase of water depth, the sedimentary area of oil shale increases, especially in layers 4, 5 and 6, which are developed in the whole region, with stable thickness and high oil content (> 10%).

2. Program control

According to the sedimentary sequence diagram of the basin, Huadian Formation in Huadian oil shale mining area has developed a complete fourth-order sequence, in which the lower pyrite member is a low-water system tract, the middle oil shale member is a transgressive system tract and a high-water system tract, and the upper coal-bearing member is a regressive system tract. The number of sedimentary cycles controls the number of oil shale layers.

The transgressive system tract was formed in the rising period of lake level caused by continuous lake transgression. According to the lithologic profile, the sedimentary thickness of the lower oil shale layer (13 ~ 9 layers) is larger in the center of the basin on the side of the basin-controlling fault (F 1), and gradually pinches out towards the basin edge, which is a regressive deposit. The sand body at the bottom of this section is very developed. According to the supernormal phenomena in the stratum, it is inferred that the bottom sand body should be water inflow sand body and deposited in the water inflow system tract.

13 ~ 9 oil shale is developed in transgressive system tract, mainly from shallow lake facies to semi-deep lake facies. The lithology is mainly dark gray, gray-black mudstone and oil shale, with 3 ~ 5 layers of thin gray-dark gray toner and fine sandstone, with horizontal bedding and massive bedding. The lake basin is dominated by shallow lake-semi-deep lake facies, and the transgressive (fan) delta sedimentary system is located at the edge of the lake basin. In addition, underwater gravity flow is also developed in the transgression system tract of Huadian mining area, which is related to the extension and subsidence caused by faults.

The high water level system tract was formed in the relatively static high water level period of the lake, with the eighth oil shale, the largest flooding surface of the lake, as the bottom boundary. From the lithologic profile, the superposition of upper oil shale layers (65438 layers +0 ~ 8 layers) is a typical accretion quasi-sequence group superposition structure, and the oil shale in the whole basin is well developed and very stable in distribution (Figure 8- 16).

The 8th ~1oil shale is developed in the high-water system tract, mainly in semi-deep lake-deep lake facies, with brown, black shale and oil shale as the main lithology, and horizontal bedding is often developed. Both dark mudstone and oil shale in Beitaizi area were deposited in the period of high water level system tract, and the east is close to the fault side. Thick mudstone and oil shale are mixed with thin sandstone and siltstone, which have positive grain order characteristics and may be underwater gravity flow. The bottom of the 1 layer oil shale is dark, thick and massive homogeneous mudstone. All of the above are characterized by semi-deep lake-deep lake facies, and vertically they are characterized by high water level accretion.

Figure 8- 16 Lithologic Profile of Huadian Formation in Huadian Oil Shale Mining Area, Jilin Province

(4) Characteristics and distribution of oil shale.

1. Characteristics of oil shale

Huadian oil shale is grayish brown, brown, dark gray, dense and massive, conchoidal fracture, brown scratches, light weight, high oil content, smooth streaks carved with nails, which can be ignited with open fire, rich in animal and plant fossils and plant debris, especially the Quaternary oil shale is rich in algae and brachiopod fossils.

Huadian oil shale has concentrated mineral resources and excellent quality, and its oil content is generally 10% ~ 12%, with the highest of 24.80%. The oil content of this sampling test is 23.74%, the calorific value is 25.92 ~ 36.37 kJ/g, and the ash content is relatively low, ranging from 52.97% to 62.65438+. It belongs to oil shale with low ash and high oil content.

2. Distribution characteristics of oil shale

From the northern margin to the southern margin of the basin, in the direction of synsedimentary fault, the oil shale profile generally shows a trend from thin to thick, with the thickness of 100 ~ 120 m in the north and 240m in the south, indicating that the basin is a semi-graben stratigraphic framework and structural framework.

From the vertical sedimentary characteristics of oil shale profile, there are obvious differences between the eastern, central and western parts. The 13 ~ 9 oil shale layer in the lower part of the oil shale section extends from Dacheng sub-region to Beitaizi sub-region from bottom to top, with overlapping deposits. The 8th layer to 1 layer is consistent, forming two sedimentary sequences. This feature reveals that the early sedimentary range of oil shale profile is in Dachengzi-Gonglangtou area, with a small area. The late extensional superimposed deposits covered the whole oil shale sedimentary basin and have been preserved to this day (Figure 8- 16).

13 ~ 1 oil shale (recoverable layer) is deposited from bottom to top in this area, 13 ~ 9 oil shale is only developed in Dachengzi-Gonglangtou area, and 8 ~ 1 oil shale is developed in the whole area. Gonglangtou sedimentary oil shale has many layers and large thickness. The number of stories in the adjacent big city partition in the west decreases and the thickness becomes thinner until the Beitai partition points out; The fourth, fifth and sixth layers are the best in the whole region, and the sedimentary thickness in the west is still thinner than that in the east.

The contour map of oil shale profile shows that the northern margin of the basin is thin. 0 ~ 40m in Beitaizi District, 0 ~100m in Dachengzi-Gonglangtou District; The thickness of the southern margin fault zone is 60 ~ 240 m, and its changing trend is gradually increasing from the north side of the fault zone.

The contour map of cumulative thickness of oil shale recoverable layer shows that the thickness of Beitaizi area in the west is 5 ~ 8m, that of Dachengzi area is 10~20m ~ 20m, and that of Gonglangtou area is 20 ~ 35m. The cumulative thickness of oil shale recoverable layer gradually becomes thinner from east to west (Figure 8- 17).

Fig. 8- 17 isoline map of the fourth oil shale thickness in Huadian oil shale mining area

(v) Evaluation of oil shale resources

The resource evaluation of Huadian oil shale mining area is divided into seven calculation units: there are four fine investigation areas, namely Gonglangtou District, Dachengzi District, Beitaizi District and Miaoling District; There are two census areas, namely the southern census area and the Jingouzi census area; There are 1 forecast regions. The oil shale resources in Huadian oil shale mining area are 70523× 104t, of which 57112×104t has been proved. The recoverable resources of oil shale technology are 43119×104t, of which the recoverable resources of oil shale technology are 39 096× 104t. The shale oil resources are 6 059× 104t, of which the shale oil resources are 4 782×104t; ; The recoverable resources of shale oil technology are 3 644× 104t, and the recoverable resources of shale oil identification technology are 326/kloc-0 /×104t. The recoverable resources of shale oil are 2 733× 104t and 2 446× 104t.

The method used in the resource prediction process is: the thickness of oil shale in the prediction area is 7.96m, the weight is 1.92t/m3, the oil content is 9.52%, and the boundary is the boundary of oil shale-bearing strata in the mining area except the exploration area.