Methods Of Shale Oil Reservoir Evaluation

As the demand of oil and gas resources in the world continues to grow, and conventional oil and gas resources will be difficult to meet the demand of international energy, our concept of oil exploration begins to change, and our focus of attention gradually into the unconventional oil and gas resources.Shale oil as the unconventional energy resources has attracted more and more attention.With the deepening of the theory and the rapid development of exploration and developmengt technology, shale oil has become the hotspot of oil and gas exploration all over the world.Based on the survey of shale oil reservoir logging evaluation methods both at home and abroad, combining with the logging data, mud logging dat, geological data and core analysis data, completed the qualitative identification of shale oil reservoir, and the quantitative evaluation of geochemical parameters, physical parameters, rock mechanics parameters, and formed a relatively system of shale oil reservoir parameters log interpretation method, and eatablished a parameter logging evaluation model of shale oil reservoir which is consistent with the geological characteristics of the S block.Reservoir qualitative recognition:shale oil reservoirs in well logging curve have typical characteristics of "two low four high", which are the high acoustic time, high natural gamma ray, high resistivity value, high compensation neutron, low photoelectric absorption cross section and low density; Due to the presence of organic matter in the reservoir, which can enhance the adsorption capacity of clay for uranium ions, thus gamma ray and KTH gamma ray without uranium in shale oil reservoir will have obvious difference; Assumes that the components of hydrocarbon source rock and non-hydrocarbon source rock strata are consistent or basically unchanged, by means of the porosity curve or natural gamma curve and resistivity curves are specialiy calibrated, so as to make the porosity curve or natural gamma curve and resistivity curve in the hydrocarbon source rock in parallel or basic coincidence, and where the hydrocarbon source rocks exist will have a certain range.Quantitative evaluation of reservoir parameters mainly includes the following several components:Evaluation of the organic geochemical parameters (organic-matter maturity, organic-matter abundance):based on the linear fitting of vitrinite reflectance and depth to establish the evaluation model of vitrinite reflectance,which can evaluate organic-matter maturity very well; In the process of organic-matter abundance evaluation we need to according to the actual conditions of the area, and the applicable conditions of the methods, to choose a reasonable method:when the lithology of shale oil is basically remain unchanged, and don’t have the influence of conductive minerals, the method that overlapping the porosity curve and natural gamma curve with resistivity curve has the very good application effect; the improved method by overlapping the porosity curve and natural gamma curve with resistivity curve can not only solve the problem how to determin the baseline as the lithology of shale oil reservoir is complex and complicated, but also make the evaluation results of the total organic carbon content calculation more accurate,and the process is more simple and convenient; the method of curve fitting can quickly build the model of total organic carbon content, but exists limitations in different aeeas, at the same time, this method has certain dependence to the sample data; BP neural network can deal with the complex nonlinear relationship between the output signal and the input signal well, and can solve the problem of the preference in the process of evaluation effectively, which can have a good application effect where the lithology of shale oil reservoir is complex and complicated, but due to the need of the sample data, which has a certain degree of dependence to the core data; Kerogen transformation method involves the setting of multiple parameters, and the error of the kerogen content will directly affect to the calculation accuracy of total organic carbon content, therefore, setting the reasonable parameters is an important prerequisite for the method can have the good application effect.Evaluation of physical parameters (porosity, permeability, saturation):the optimization method and the neural network method in the process of evaluation of porosity in shale oil reservoirs both have a good effect based on the rock core standardization, and whose errors are small. Optimization method has a good geological application effect for the reservoirs evaluation where the lithology is complex; Due to neural network method can deal with the complicated nonlinear relationship between input and output signal, which has wide application areas to evaluate the reservoir whose lithology is complex; Mineral composition method and neural network method are more universa in the process of shale oil reservoir permeability evaluation, and the mineralogical method considering the factors such as pore structure and mineral components, which can choose the mineral components according to the geological characteristics of different blocks, has the very good universality. The improved formula of Lambda in the shale oil reservoir has a good effect when evaluate the permeability; Conductive model method and the neural network method compared with Archie derivative method in the process of shale oil reservoir saturation evaluation have a better application effect, whose errors are relatively smaller. Conductive model method has more superiority and universality to evaluate the saturation of the reservoir whose lithology is complex, which is an ideal evaluation method.Evaluation of rock mechanics parameters (elastic coefficient, coefficient of hardness, brittleness coefficient):according to the longitudinal and shear wave logging data to quantitative evaluate the rock mechanics parameters, under comprehensive analysis, found that the set of rock mechanics parameters has the very good consistency in nature on the rock mechanics, which means that can guide the engineering development of shale oil reservoir. Elastic coefficient method and mineralogical method have the very good consistency in the evaluation of rock brittleness, therefore, in the absence of acoustic full waveform logging data, we can evaluate the rock brittleness by the mineralogical method.In conclusion, through the comprehensive processing and interpretation of typical shale oil well in the S block, to lay the foundation of method and theory for the identification of the shale oil reservoir, evaluation of organic geochemical parameters, evaluation of physical parameters, and assessment of rock mechanics parameters, and to provide the technical support for the follow-up development of shale oil reservoir in the S block.