Study On The Evaluation Methods Of Low Permeability Reservoir In M Area Of Ordos Basin

Reservoir comprehensive evaluation is an important work of guiding oil and gas exploration and development.It is usually divided into two stages,which are exploration and development.The exploration stage mainly uses the geological and seismic data in the research area,and combines with a small amount of drilling and logging technology,the potential oil and gas reservoir is properly divided.The core problems in the process of evaluation include:the determination of evaluation parameters and its weight distribution problems in the evaluation parameters system,the selection of reservoir comprehensive evaluation method and so on.Low permeability oilfield with abundant reserve is widely distributed in our country.However,so far,its production is still limited.In this paper,the study area is Jiyuan area and the horizon is the chang 2 oil group,which is located in the northwest of ordos basin.The main characteristics of the oil-field development are low porosity and low permeability.Because of the uncertainty of the single factor evaluation,it is necessary to establish a set of evaluation systems which are suitable for low permeability reservoir.Therefore,according to the practical geological conditions of the study area and the concrete analysis,this paper optimizes the permeability,porosity,fluid saturation,mainstream throat radius,maximum pore radius,sorting coefficient,amount and type of clay,starting pressure gradient,underground crude oil viscosity,maximum mercury injection saturation,displacement pressure and so on,for the further study.On the basis of above reservoir evaluation parameters,this paper establishes two sets of reservoir comprehensive evaluation methods.First is the fuzzy comprehensive evaluation model of low permeability reservoir,mainly includes:through the analysis of all kinds of methods of determining weight,finally chooses the analytic hierarchy process(ahp)to determine the weight of evaluation parameters and the parameters are analyzed with the sensitivity analysis.Finally through the analysis and verification of the classification results,the reservoir is divided into four types.Second is a comprehensive evaluation model of low permeability reservoir based on data mining,mainly includes:the parameters are analyzed by factor analysis in multivariate statistical analysis,then analyzes the application effect of four different clustering methods in data mining,chooses the best clustering method for reservoir classification.Perfects the attribution type of all samples through discriminant analysis,the reservoir is divided into four types,too.Finally,the stability of the algorithm is verified.In the process of reservoir evaluation,the influence of the subjective factors is reduced greatly through using Matlab and SPSS to process data.Through analysis and comparison the results of the two comprehensive evaluation methods,it shows that type-? reservoir is commonly found out in the research region.The proportion of type-? reservoir is the minimum,and,in the chang 312 and 222 small layers,type-? reservoir is relatively well developed.Its classification conforms to the actual geological characteristics.Thereby,the rationality and validity of these two kinds of analysis methods is verified.