The Critical Conditions Of Shale Oil Accumulation And Prediction Of Favorble Areas

Shale oil in China is mainly distributed in five basins,which are Junggar Basin,Songliao Basin,Ordos Basin,Sichuan Basin and Bohai Bay basin.It is estimated that recoverable oil shale resources from main basins in China are about 30×10⁸-60×10⁸tones.These resources are of great economic value.Compared with conventional reservoir,shale has the characteristics of low porosity and permeability and the pore structures is complicated,which leads to the huge challenge for exploration and development of shale oil.In this thesis,the formation conditions of shale oil,main control factors of shale oil enrichment and evaluation methods of shale oil enrichment are researched respectively through SEM field-emission scanning electronic microscope,gas adsorption experiment,nuclear magnetic resonance,rock pyrolysis,gas expansion method,pulse permeability test.From discussed above,we can learn that:?1?The quantity hydrocarbon generation from of source rocks is determined by the abundance,type,maturity of organic matter;Because the organic matter pores from study area are not considerable development,the development of inorganic pores and microfractures from reservoir rocks provide a space for the occurrence of shale oil;The geochemical conditions and reservoir conditions of shale oil determine the degree of enrichment of shale oil.The development of abnormal high pressure plays an important role in primary migration of shale oil and gas.In addition,it is not only good for sealing oil and gas,but also beneficial to the late fracturing exploitation of shale oil.?2?The shale lithofacies in the lower section of the third number of Shahejie Formation in Zhanhua Sag are divided into nine lithofacies according to the organic matter abundance,sedimentary structure,rock composition,which are organic-rich laminated argillaceous limestone and lime mudstone,organic-rich inter-bedded argillaceous limestone and lime mudstone,organic-contained inter-bedded argillaceous limestone and lime mudstone,organic-contained massive mudstone.The most developed six types of lithofacies in Zhanhua Sag include organic-rich laminated argillaceous limestone and lime mudstone,organic-rich inter-bedded argillaceous limestone and lime mudstone,organic-contained laminated argillaceous limestone,organic-contained inter-bedded argillaceous limestone.The organic-rich laminated lithofacies has the characteristics of high organic matter abundance and strong hydrocarbon producing potential.Otherwise,the development of laminaed increase the occurrence space of oil and gas,so that its reservoir capability is also great.So organic-rich laminated argillaceous limestone and lime mudstone are the best lithofacies of shale oil enrichment.?3?The porosity types of shale oil enrichment from different phase are determined by comparing the experimental results from gas adsorption of shales which are before and after extracted by trichloromethane,observing the change of pore volume and surface area in micropores,mesopores and macropores,combining with the pyrolysis hydrocarbon and irreducible oil saturation from the experiments of nuclear magnetic resonance.Therefore,it is also confirmed that pore structures have an effect on shale oil enrichment.?4?The wettability of rock is confirmed by nuclear magnetic resonance?NMR?which is an efficient,convenient and harmless to shale samples and by comparing the ability of absorbing water and oil from the same shale samples;The wettability characteristics which is beneficial to shale oil enrichment is confirmed by comparing the features of the organic matter abundance and oil potential from different wettability shale samples.?5?The shale oil enrichment method of PSI?Pore Saturation Index?that combined the characteristic that source rock is just the reservoir itself is established by combining pyrolysis hydrocarbon?S₁?,organic matter abundance?TOC?,porosity???and permeability?k?;The critical geological,geochemical and reservoir conditions of shale oil enrichment are confirmed through the shale oil enrichment method in study area with PSI.