The Optimization Of Enhancing Oil Recovery Method For Tight Oil

As the shale gas has been successfully exploited in North America,the tight oil,also stored in low permeability media and called as ‘black oil',has gained more and more attention.The tight oil has great potential in China with a reserve of 106.7×108¹15.5×108t,mainly distributing in Erdos Basin,Sichuan Basin,Bohai Basin and Junggar Basin.Tight oil refers to the oil stored in low permeability media,lower than 0.1 md.The tight oil has been developed successfully in North America.However,China is still as the start stage to develop this new unconventional source.Since the deposition is continental in China,while it is marine in North America,it is more difficult to utilize the resource in China.We cannot use their experiences and lessons directly.We have to find a way by ourselves.This dissertation mainly focuses on physical experiments and numerical simulations in order to find an effective way to exploit the tight oil reservoir in Lucaogou formation in Xinjiang Oil Field by using the rock cores and crude oil from the field.First,the characteristics of tight rock have been analysed.The porosity and permeability have been measured after cores extracted.The stress sensitivity has been analysed and measured by SEM and physical experiments.During this process,the start-pressure gradient has also been measured.The wettability of rock with different fluid systems have been analysed by X-ray diffraction,crude oil four components analysis and measurement of contact angle.Then the experiments of different developing methods have been conducted.The oil recovery rates of water huff and puff,surfactant-water huff and puff,CO₂ huff and puff have been compared.The results indicate that surfactant-water huff and puff can extract more oil from the cores than water huff and puff,as it may change the wettability of rock to water wettability.The oil extracted by CO₂ huff and puff is more than other methods.Finally,based on the results above,numerical simulation experiments of CO₂ huff and puff have been conducted.The injection time,injection parameters have been investigated.Basing on the result,the productivity prediction of CO₂ huff and puff has been conducted.