Research On Characteristics Of Oil Shale Of Cenozoic Fault Basin In Northeast Area

The northeast area is an important energy and old industry base in China, which oil shale reserves are 48% of the whole oil shale reserves in China, and the oil shale resources have great development value. With the decline of oil and gas production year after year, oil shale will become an important alternative energy in the northeast area. At present, the research of oil shale in the northeast area emphasized particularly on the classification, development and utilization of oil shale, but on the genetic mechanism and formation environment of oil shale resource is still comparatively rare. Thus, it has great realistic significance to develop systematically the study on the genetic mechanism and formation environment of oil shale resourceThe thesis dissected the characters of oil shale in three Cenozoic fault basins of northeast area, that is Dalianhe basin, Huadian basin and Fushun basin. These basins lied inside the Yilan-Yitong Fault Belt and Duhua-Mishan Fault Belt, which is the northward branch fault of Tanlu Fault Belt. The formation and distribution of oil shale have intimate relationship with the action of the faults, the oil shale developed in the Cenozoic paleogene formations.The oil shale in Yilan basin deposited in the Coal-Oil Shale Member and Oil Shale Member of Dalianhe Formation in Eocene -Oligocene. There are 5 pay oil shale beds in the Coal-Oil Shale Member, the oil shale beds are interbedded with the coal beds and are the top layer of coal beds. The thickness is very thin, but the oil shale yield is very high (about 5%). The thick oil shale beds deposited in the Oil Shale Member, which distribution is vast, and the zone position is very steady, the oil shale yield is low (less than 3.5%). The oil shale in Huadian basindeposited in the Oil Shale Member of Huadian Formation in Eocene–Oligocene . There are 26 pay oil shale beds, and 13 beds are recoverable in it, which oil shale yield is high (about 10%). The oil shale in Fushun basin deposited in the Jijuntun Formation in Eocene, the thickness is very huge. The oil shale can be divided into poor and rich beds, the oil shale yield of rich oil shale beds is higher (more than 5%), the oil shale have industrial development value.By the analysis of X-ray diffraction, scanning scanning electron microscope and organic geochemistry testing, the components of oil shale in target areas are detrital mineral such as quartz, calcite, feldspar and layered silicated clay mineral such as kaolinite, andreattite, goeschwitzite. According to the chemical element analysis of kerogen, the oil shale is mainly consisted of carbon, hydrogen, oxygen and nitrogen element, the oil shale yield has positive relationship with the content of organic carbon. According to the ratios of elements (H/C and O/C) and the relationship between hydrogen index and Tmax, Organic types of oil shale in target areas consist of the types I, II1 and II2 kerogen. the vitrinite reflectance (Ro) of oil shale is less than 0.5 percent, the maximum temperature of pyrolysis yield of hydrocarbons (Tmax) is more than 429℃and less than 446℃, which reflected that the thermal evolution degree in target areas is in the prematurity stage.According to the characters of palaeotectonics, rock types and primary sedimentary structure, Yilan basin mainly developed four kinds of sedimentary facies including alluvial fan, fan delta, lake, gravity flow facies and nine kinds of sedimentary subfacies during the sedimentary period of the Dalianhe Formation.The lacustrine bog and sub-deep-deep lake are the optimum facies for oil shale development. The vertical filling series of sedimentary facies is alluvial fan-fan delta-alluvial fan-lower lake-sub-deep lake-deep lake-lower lake-fan delta facies. Huadian basin developed two kinds of sedimentary types including delta and lake facies during the sedimentary period of the Huadian Formation, the oil shale developed in lower lake and sub-deep lake. The vertical filling series of sedimentary facies is delta-lower lake-sub-deep-delta facies. The Guchengzi,Jijuntun and Xiloutian Formation of Fushun basin deposited lacustrine facies, and the oil shale mainly deposited in the sub-deep-deep lake of Jijuntun Formation. The three basins all displayed the filled process that the sedimentary water changed gradually from low to high to low.The mineralization of oil shale in the three basins of the target areas is controlled by the tectonic action, palaeoclimate and sedimentary environment. The tectonic action controlled the formation, distribution and the variation in thickness of oil shale, which showed that the thickness was biggest by near the side of the fault controlling the basin and became thinner to the boundary of the basin. synsedimentary fault in the basins controlled the fragment thicken and thin of oil shale. The optimum palaeoclimatic conditions of oil shale deposit is warm-moist semitropical climate, under the condition of warm-moist climate, the plants blossom, the organic materials in the lake basin are rich, which are favor of the formation of oil shale. The distribution of poor and rich oil shale beds and the types of organic materials in the three basins are controlled by the change of palaeoclimate. Different types of oil shale deposited in different sedimentary environments, the dark oil shale with type I kerogen developed in deep-sub-deep lake facies, the oil shale with type II kerogen developed in limnetic facies.According to the observation on the field sections, combinated with the drilling and log materials, the thesis analyzed the sequence stratigraphic charater in target area. The Dalianhe Formation of Yilan basin is consisted of a whole cycle including Low System Tract (LST), Transgressive System Tract (TST), High System Tract (HST) and Regressive System Tract (RST). Huadian basin is also consisted of a whole cycle including Low System Tract (LST), Transgressive System Tract (TST), High System Tract (HST) and Regressive System Tract (RST). The Jijuntun Formation of Fushun basin is consisted of a whole three order sequence (sequence I ), and the Xiloutian Formation is divided into twosequences including sequence II and sequenceⅢ.According to the study on the areal structure, geologic setting, sedimentary environment and evolvement, sequence stratigraphy in target area, the thesis established the metallogenetic model of oil shale in fault basin. The oil shale mainly developed in the Transgressive System Tract (TST) and High System Tract (HST). The Transgressive System Tract (TST) developed alluvial fan depositional system by the side of steep slope of the lake basin, developed lower lake or limnetic facies to the inside of the lake basin, and developed (fan) delta depositional system by the side of gentle slope, the oil shale deposited in the lower lake or limnetic sedimentary environment. The High System Tract (HST) developed delta depositional system by the side of gentle slope of lake basin, and developed sub-deep-deep sedimentary facies to the central of the lake. The thick oil shale beds can easily form during this time.