Identification Of Preferential Channel In Yuan284 Block

After long-term water flooding,the old oilfield may form preferential channel,also known as large pore channel,in the later stage of development.Its formation is mainly affected by the original formation state and later development factors.After the formation of preferential channel,the heterogeneity of reservoir is aggravated.Injection water will ineffective cycle,reduce sweep coefficient,and ultimately result in poor reservoir development effect.Therefore,it is of great significance to identify preferential channel.Yuan284 block was selected as the research area to study the static geological characteristics of the block and understand its heterogeneity and reservoir physical properties.From the production well output,water cut and water cut rising rate with time,we know that some wells in Yuan284 area have entered the middle and high water cut stage in a short time,and the water cut rate has reached more than 80%.In order to identify the preferential channel and improve the efficiency of water flooding,a large number of domestic and foreign literatures have been investigated.Combining with geology,seepage,fuzzy mathematics and other disciplines,the following research results have been achieved:(1)Based on the analysis of the static geological characteristics and production dynamic characteristics of block Yuan284,the factors affecting the formation of preferential channels are analyzed.It is found that the formation of preferential channels in block Yuan284 is mainly affected by fractures,which are divided into natural fractures and dynamic fractures.(2)Five methods are used to identify the preferential channel in block Yuan284,including direct method of field data,tracer test method,well test data method,production dynamic data method and grey relational analysis method,and the advantages and disadvantages of the five methods for identifying preferential channel are compared.(3)According to the actual situation of block Yuan284,a method of identifying the preferential channel in the block by comprehensive fuzzy evaluation is proposed.The method uses static and dynamic data synthetically to determine the weight and membership function of the evaluation index,and establishes the identification model and evaluation criteria of the fuzzy evaluation,so as to discriminate the preferential channel.Using this method,the preferential channels of typical well groups in block Yuan284 are identified,and the recognition results are verified by using streamline numerical simulation model.(4)On the basis of qualitative identification of preferential channels,taking fully into account the dynamic development data of oilfields and combining with percolation theory,the paper proposes to calculate the volume of dominant channels by using the evaluation model of excess water-grey correlation analysis.According to seepage principle and Cayman-Kozeny formula,the permeability and fracture width of preferential channel in block Yuan284 are calculated.(5)Preferential Channel identification software of block Yuan284 was developed by using Visual Basic language.