| Qiongbei Basin is located in north of Hainan Province, with area of 1.2×104km2. Qiongbei Basin is a Cenozoic depression basin with NE-SW strike overall. Basin structure is controlled by 7 fractures, along EW, NE,NW directions, the basin is divided into 6 secondary depression of Eman, Changpo, Fushan,Haikou,Dongzhaigang, Puqian and 2 secondary uplifts of Lingao, Yunlong, oil shale minerals are found in Changpo Depression.Danzhou oil shale is mainly gray bro wn, dark gray and dark gray commonly with horizontal bedding and other primary structures, fossils of animals and plants are found in drilling cores, mainly herbaceous plants and ostracods fossil. X-ray diffraction analysis showed that oil shale in research area consists mainly of quartz(61%), clay mineral illite(15%), calcite(10%), clay mineral kaolinite(5%) and pyrite(7 %) and other minerals. Macerals of oil shale in research area are mainly alginite. Carbon(C), Hydrogen(H), Oxygen(O) are the main organic matter elements, content of Carbon(C) is 75.11% in average, content of Hydrogen(H) is 8.65 % in average, content of Oxygen(O) is 10.13% in average, the rest is Nitrogen(N) and Sulfur(S) element. Of oil shale of the research area, H / C is between 1.03 to 1.75, O / C is between 0.09 to 0.12, which indicates that organic matter of the oil shale is mainly sapropel(type I), the other is humic sapropel(type Ⅱ1). Vitrinite reflectance Ro of Danzhou oil shale is between 0.46% and 0.54%, pyrolysis peak temperature(Tmax) is between 429 ℃ to 443 ℃, indicating that oil shale in the target area is in immature- low mature stage.The quality characteristics study of oil shale in target area includes analysis of oil content, industrial components, calorific value, carbon and sulfur content et al.. It’s showed that oil content of Danzhou oil shale oil was 5.10%, while reaching industry standard, but the oil shale still belongs to medium-quality oil shale with oil content of less than 10%, the calorific value is higher with 8.79 MJ/kg; ash content of oil shale samples in the Changpo Depression is up to 70.51%, with the lowest of 32.74% and an average of 63.56%, belonging to oil shale with medium ash content; total carbon content is 19.85%, total sulfur content 0.70% in average,belonging to oil shale with ultra-low sulfur. In addition, data analysis showed that oil content was negatively correlated with ash content, while positively correlated with calorific value.Danzhou oil shale occurred in 4th member in Changpo Formation, mainly in the south of the Changpo Depression. The oil shale occurred in bedding in plain, and naturally pinched out along both ends of strike, the thickness is vertically increasing along the dip direction towards the north with monoclinic-like occurrence. In accordance with the variation of oil shale occurrence position and lithologic member, oil shale mineral layers can be divided into three seams, lower, middle and upper seam.Through field drill core observation in the study area and cross-sectional data logging analysis, the Miocene Changpo Formation in the study area can be further subdivided as talus accumulation facies in 1st member of Changpo Formation, lakeshore-shallow lake facies in the 2nd member of Changpo Formation, deep lake facies in the 3rd member of Changpo Formation, and lacustrine and swamp facies in the 4th member of Changpo Formation-the main oil shale mineral occurence layer. Ancient lake water salinity in the research area is indicated by barium and strontium ratio, it’s verified that the deposition environment of Danzhou oil shale was freshwater; then anoxic reducing conditions is derived from V/(V + Ni) ratio. Through analysis of oil shale mineralization control factors, sources of organic matter are rich in the lacustrine basin during development of the 4th member of Changpo Formation, the overall lacustrine basin was in relatively subsiding development stage. Suitable water depth, reducing conditions by stratification and algae oxygen consumption formed oil shale minerals in the lacustrine-swamp facies in Changpo Formation in Danzhou.China’s current oil shale has formed a new multi-domain and multi-directional comprehensive utilization and development model with traditional field developed and supplemented by new fields. Utilization potential of oil shale in the research area is huge with enrichment of Aluminum(Al), Phosphorus(P), trace element Cesium(Cs) and rare earth elements Samarium(Sm), Europium(Eu), Holmium(Ho) in the ash component According to quality and geochemical component characteristics of oil shale in the study area, combined with the local actual situation, traditional areas like extraction of shale oil, heating to generate electricity, ash as road building materials can be developed, new areas like development of agricultural fertilizers, fireproof materials and extraction of metal ores and rare earth minerals can also be explored. |
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