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Classification And Formative Effects Of Sandstone Reservoirs With Low Recovery Efficiency

Posted on:2006-12-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:H Z SunFull Text:PDF
GTID:1100360152485993Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
Based on the data of Sartu, Putaohua and Gaotaizhi oil bearing groups, this paper studies the characteristics of the sandstone reservoirs with low water/polymer recovery efficiency in each oil bearing group, criterion of classification, type-recognition in the well logging profile and their formative effects. Then, it discusses the potential and methods for the low recovery reservoirs. First of all, the paper studies the basic characteristics of the reservoir in each oil-bearing groups including the distribution, genetic types, diageneses, pore types and textures, porosity, permeability, original and current oil saturation of the sands in the study area. Based on the permeability data interpreted from well loggings, the macro-heterogeneities of the sands have been studied, such as the heterogeneity between the layers, the heterogeneity within the layer and the horizontal heterogeneity for each layer of the sands in the area as well as the correlation between the macro-heterogeneities and water/polymer flooding recovery efficiency. With the micro-pore textures of sandstone being studied, petrographic image analysis system has been used to measure 33 types of pore-textural parameters in 2-dimentions from 92 core plug samples. These parameters have a very high correlation coefficient with the permeability and recovery efficiency data measured from the core plugs. To zero in on the parameters mainly influencing the water recovery efficiency, 6 core plugs with different pore textures have been chosen to perform a water-flooding simulation test. Under different injecting conditions, 10 parameters have been chosen because they have closer correlation with the oil recovery efficiency during the test. Two parameters are distinguished from the 10 and their difference is taken as the pore shape index, which is especially important for the reservoir classification. To make the classification of reservoir accurate and objective, each formative effect of the reservoirs with low recovery efficiency has been examined thoroughly from the macro scale to the micro one. While the genetic types of sands, the patterns of sand vertical sequences, the developing sand complex, the developing well patterns and distances between the injection and production wells have been analyzed to find the effects which mainly control the water flooding recovery efficiency of the sands in the area. The pore textural parameters from 1597 core-plug conventional petrophysical data in two cored wells are inversed, grouped and calculated to form the heterogeneous parameters according to sand layers to make the heterogeneous parameters full of pore textural characteristics. Through analyzing, a conclusion has been reached that the pore shape heterogeneity is the main formative effect of the reservoirs with low recovery efficiency in the area because compared with the heterogeneous parameters of core-plug permeability, the heterogeneous parameters of inversed from image analysis pore textural data have a very closer correlation with water/polymer flooding recovery efficiency data. The classification of reservoirs with low recovery efficiency is made in a way from microscopic scale to macroscopic one. First, the pore shape index is used in classification among the 92 core-plug samples. Second, the characteristics of petrography and pore textures in each type of sand are studied to recognize the regular pattern of pore textures among different types of sands. Third, the classification method is used in cored wells to separate the low recovery reservoirs from the higher ones according to their marginal sand thickness and oil sand thickness. Finally, the method is expanded to the well logging profile. In order to apply the classification system in the oilfield, Delphi5.0 is used for developing a computer program to operate the whole classification system in a PC with windows 98 and upper version. With the computer program, 49 infilling well data in the area have been processed and each sand with low recovery efficiency in a well profile is recognized and classifi...
Keywords/Search Tags:Daqing placanticline, Reservoir heterogeneity, Reservoirs with lowrecovery efficiency, Image analysis, Pore texture
PDF Full Text Request
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