Resource evaluation of Fengshan oil shale mining area in Fengning, Hebei Province

Fengning Fengshan Oil Shale-bearing Mining Area is located in the southeast of Fengning County, Hebei Province, on the northwest edge of Fengshan Town, with geographical coordinates of11712' east longitude; North latitude 4 1 14'. This area belongs to the geographical environment of low mountains. The mining area is located in Fengning Town with convenient transportation. It is the transportation hub of Fengning County. It can reach Dage, which is 70 kilometers apart, and Chengde, which is 97 kilometers apart. Chengde can take Beijing-Chengde Railway or Tianjin-Chengde Railway to all parts of China.

I Fengshan exploration area

(1) Geological background

1. structural points

Generally speaking, the structure of the exploration area is relatively simple, and folds and faults are not well developed, which are confined to the basin. The fault plane strikes ne 30 ~ 50 and tends to NW, and the strata at the north and south ends gradually turn to NW and tilt to NE and SW respectively, which makes the whole basin have the nature of inclined oblique structure. There are small folds and bends in some places. There are two main faults: Yuanbaoshangou translation fault: this fault is a flat thrust fault with strike N40 ~ 45 W, dip NE, dip angle of 80 and fault line length of 400 meters. Baishilai normal fault: this fault is located in the northwest of the mining area, with the fault plane nearly trending east and west, dipping southward with an inclination angle of 65. This fault controls the northern boundary of this area. The fault line passes through Sanchakou, Baishilai, Shangba and other places to Shangguanyingzi, and its scale is large, which is consistent with Lingxuan deep fault.

2. Stratigraphic characteristics

The strata in the mining area are mainly Mesozoic volcanic rocks of Zhangjiakou Formation of Upper Jurassic and sedimentary rocks of Xiguayuan Formation of Lower Cretaceous, followed by pre-Sinian metamorphic rock series and Neogene. The specific stratum lithology and characteristics from old to new are described as follows:

(1) Pre-Sinian System (Z).

The pre-Sinian system is mainly distributed in the edge of the mining area, and the main lithology is hornblende gneiss, hornblende plagioclase gneiss and biotite plagioclase gneiss.

(2) Upper Jurassic (JBOY3).

Zhangjiakou Formation (J3z): The lower part of this formation is purplish red rhyolite and quartz porphyry, and the upper part is grayish purple andesite with pore structure and tuffaceous breccia.

(3) Lower Cretaceous (K 1).

Xiguayuan Formation (K 1x): This stratum is divided into seven layers, which are described as follows from bottom to top:

Bottom conglomerate layer: yellow and purple sandstone and grayish purple tuffaceous conglomerate;

Lower shale: interbedded with gray argillaceous shale and yellow sandy shale;

Lower oil shale layer: black and gray-black thick oil shale mixed with gray shale and thin sandstone;

Medium shale: interbedded with yellow thin sandstone, gray shale and oil shale;

Upper oil shale layer: this layer is gray shale, black flake oil shale and oil shale;

Upper sandstone shale: mainly composed of sandy shale and sandstone, with conglomerate lentils locally.

(4) Neogene.

The Neogene strata in the mining area are mainly loess and river alluvium.

(2) Characteristics of oil shale

1. Characteristics of oil shale

The oil shale in this area is mainly tar asphaltene shale, which is brownish black and grayish brown. The ore is dense, massive and flaky, with undeveloped foliation, brown stripes and strong toughness. After weathering, it is gray clay, which is oily when hammered and easy to burn. After sintering, the slag is powder gray and has strong cohesiveness. The weight of ore is 2.26 ~ 2.44 t/m3, the porosity is about 6%, and the calorific value is 2.7MJ/kg.

2. Analysis of oil shale formation environment

The oil shale-bearing system in this mining area belongs to the Mesozoic Lower Cretaceous small-scale continental closed shallow lake sedimentary deposit. At first, there was a quiet lake basin in the depression of the mining area, which was beneficial to the accumulation and formation of the original materials of oil shale. Oil shale is formed by the accumulation of sapropelic mud in lake basin and the supplement of terrigenous organic matter. Later, due to the deepening of the water body and the continuous acceptance of sediments, the sediments were quickly buried in an anoxic environment. Through the activity of anaerobic bacteria, organic matter is reduced and degraded, which changes the organic matter and eventually forms tar or kerogen.

3. Distribution characteristics of oil shale

The oil shale in this area is mainly developed in the middle of Cretaceous Xiguayuan Formation, with a distribution area of 40km2, from Wangluozigou to Taolaiyingzigou, with a length of 12km and a width of about 4km. The total thickness of coal seam is 3 1.82m, and the deposit is produced by layered and lenticular multi-layer oil shale, with about 26 oil shale layers, mainly distributed in the south and north lower dam sections and the central area of the mining area.

(3) Evaluation of oil shale resources

1. Analysis of geological work degree

(1) Geological exploration work.

When the mineral deposits in this area were pseudo-full, some Japanese did investigation, wrote a general survey report, made a preliminary division of the strata, and made a negative evaluation on whether there was oil shale output. From 65438 to 0958, the second detachment of the former seventh geological brigade evaluated the mining area, and the investigation found that the oil shale resources in this area had great prospects. In July of the same year, the former Second Geological Brigade began exploration work in this area, which lasted until July of 196 1, and carried out work on the ore body shape, structural characteristics, oil shale output, tar change law and oil shale reserves in this mining area.

(2) Degree and accuracy of geological exploration.

Drilling is the main method to obtain evaluation data in this area. Use the grid of 1000× 1000m to calculate the reserves of C 1, and use the grid of 1000×2000m to calculate the reserves of C2. The reserves of C 1 are 8,940.8 million tons, the reserves of C2 are 720,898.46 million tons ... The grade of C 1+C2 is 889,839.26 million tons, and the exploration degree has reached a detailed survey.

2. Resource evaluation

The resource evaluation results show that the oil shale reserves in this exploration area are 29.47 million tons, the proven reserves are 29.47 million tons, the technically recoverable reserves are15.73 million tons, and the proven technically recoverable reserves are15.73 million tons. The shale oil reserves are 6.5438+0.3 million t, and the proven reserves are 6.5438+0.3 million t, 700,000 t and 700,000 t respectively. The recoverable reserves of shale oil are 520,000 tons, and the recoverable reserves of shale oil are 520,000 tons ... This area belongs to small and medium-sized oil shale deposit area.

Second, Fengshan forecast area

This area is the peripheral prediction area of Fengshan exploration area, and its geographical location is: north latitude1171',north latitude 4 1 14'. Its structural and stratigraphic characteristics are basically similar to those in the exploration area, so they will not be described here.

According to the geological characteristics of Fengshan exploration area in Fengning and the comprehensive analysis of regional geological data, it is considered that the oil shale in this prediction area was formed in lacustrine facies. The humid climate during the metallogenic period is beneficial to the development of oil shale. On this basis, the oil shale resources in Fengning prediction area are predicted by analogy with the development characteristics of the Lower Cretaceous Watermelon Formation in Fengning mining area. It is speculated that the oil shale in the prediction area exists in the strata of the Lower Cretaceous Xiguayuan Formation, mainly with 26 layers, which is the sedimentary product of shallow lake basin. The thickness of coal seam is 30.85m, the area of coal seam is 0.29 km2, the dip angle of coal seam is18 ~ 30, the buried depth is 30 ~ 440m, the weight of oil shale is 2.38t/m3, and the oil content is 4.55.

When predicting resource reserves, extrapolation is made according to the layering, thickness, oil content and weight of oil shale in the known exploration area, and the effective area of the prediction area is calculated by the product of the effective area of Fengshan exploration area and the predicted area. The resources of Fengshan prediction area are evaluated. The results of resource evaluation show that the oil shale resources in this prediction area are 265,438+500,000 t, the potential resources are 265,438+500,000 t, the technically recoverable resources are 7.53 million tons and the potential technically recoverable resources are 7.53 million tons. Shale oil reserves are 990,000 tons, potential resources are 990,000 tons, technical recoverable resources are 340,000 tons, potential technical recoverable resources are 340,000 tons ... shale oil recoverable resources are 260,000 tons, and potential recoverable resources are 260,000 tons.

Through the comprehensive analysis of the above two areas, it can be known that the oil shale resource reserves in this mining area are 50.97 million tons, the proven resource reserves are 29.47 million tons, the potential resource reserves are 265.438+500,000 tons, the technically recoverable resource reserves are 23.26 million tons, the proven technically recoverable resource reserves are15.73 million tons, and the potential technically recoverable resource reserves are 7.53 million tons. Shale oil reserves are 2.29 million tons, with proven reserves of 6.5438+300,000 tons, potential resources of 990,000 tons, technically recoverable resources of 6.5438+040 million tons, proven technically recoverable resources of 700,000 tons and potential technically recoverable resources of 340,000 tons. The recoverable reserves of shale oil are 780,000 tons, 520,000 tons and 260,000 tons respectively.