Research On Reservoir Characteristics Of Oil Shale During Heating In Songliao Basin

Oil shale is an important unconventional energy source in China.A great deal of exploration and development have been carried out in recent years.In this paper,in-situ mining experiment area of Qingshankou and Nenjiang Formation oil shale in Southeast Uplift Songliao Basin was preferred to carry out phased low temperature carbonization experiment in laboratory,and the organic matter change characteristics and oil shale reservoir evolution law in oil shale can be revealed.This study will provide a scientific basis for oil shale in situ mining experiment.The optimized oil shale research horizon is fourth layer of Qingshankou Formation and third layer of Nenjiang Formation.Qingshankou fourth layer oil shale quality is better,and the highest rate is more than 15%.Meanwhile the main oil-bearing rate is 5-8%,and the distribution of oil shale is stably with 3-5m thickness.Nenjiang third layer oil shale has maximum thickness with stable distribution.However the oil shale quality is relatively poor(max.oil yield is 8%),and the main oil ratio range of 4-6%,while the oil shale thickness between 8-15 meters.At this stage,shale oil has been obtained by in-situ heating in the two layers.Based on systematic research at home and abroad,China's Zhongcheng Company independent research and development of in-situ underground mining technology,and obtained China's first barrel of oil shale in situ.Jilin University in laboratory successfully developed three in-situ mining techniques,such as supercritical water,high pressure-frequency point and local heating in situ paralysis chemical method.The third technique has been successful in the field.In situ heating technology abroad are mainly include combustion heating technology(LETC in situ combustion retorting technology and MIS Technology),physical heating technology(ICP technology,Exxon Mobil technology,GFCTM technology,Crush technology and AMSO technology,RF/CF technology and Taiyuan convection heating technology).In accordance with the standard of Sinopec SH/T0508-92 oil shale determination method,high quality,medium and low-grade shale oil is selected to be heated in different stages at low temperature retort furnace.Rock pyrolysis parameters and polish-section macerals observation showed that the maturity of oil shale was in the immature stage,organic matter was mainly algae lakes biological sources.Heating process of oil shale show that the 400-475? and 475-520? as the main heating oil generation stage.In these stage,the organic matter content and hydrocarbon potential reduced largest.Meanwhile,the free hydrocarbon content showed a decreasing trend after the former increase.The calorific value of semi coke shows that high quality oil shale remains a lot of residual organic matter after carbonization at low temperature.Based on the rock pyrolysis of each heating stage oil shale samples,the data shows that the organic matter entering the mature stage in the first heating stage,and it into the middle mature stage in the second heating stage with hydrocarbon expulsion basically;then in the third heating stage,the organic matter entering the mature stage for a large number of hydrocarbon expulsion;in the fourth heating stage,the organic matter is from the mature stage into high mature stage;meanwhile,,the organic matter into the over mature stage in the fifth and sixth heating stage.X-ray diffraction test shows that in the low-temperature retorting stage,the content of quartz and feldspar in oil shale has little change,calcite will be reduced in high temperature heating stage.The clay mineral composition can change regularly,in low temperature stage,clay minerals are mainly illite/smectite mixed layer,with the increasing of temperature,the content of the mixed layer of illite/smectite and kaolinite decreased,illite content increased gradually at firstly,but decreased later and disappeared,chlorite appear at the end of the heating stage.Through the observation of the massive oil shale samples after heating in low temperature carbonization process,with the increasing of heated temperature,the main cracks and a large number of micro cracks distributed along the bedding,meanwhile the crack size increases gradually and communicated with each other;the nitrogen adsorption showed that with the increasing of heated temperature,oil shale rock in the cumulative pore volume and surface area showed a gradually increasing trend;high pressure mercury display with the heating temperature increasing,the porosity and permeability of oil shale samples also showed an increasing trend;combined with the experiment and other research shows that in the heating process,with the expulsion of hydrocarbon and minerals heating,caused a large number of pores and cracks and increasing of oil shale porosity;oil and gas migration and enrichment resulted in the pressure increasing,and the porosity and the fractures are connected with each other to promote the permeability of the oil shale after heating.