Study On Logging Evaluation Methods Of Low Porosity And Low Permeability Sandstone Reservoir In JiDong Exploration Area

The influence factors of lithology,physical property,pore structure,and formation water property in low porosity and low permeability reservoirs,that resulting in the difficulty of calculation of reservoir parameters and oil-water layer response characteristics are complex,so it is of important significance to carry out the logging evaluation of reservoir for improving the success rate of oil and gas exploration.In view of the geological characteristics of the reservoir area,the research work has been carried out in terms of the characteristics of "four-property relationship",the interpretation and modeling of reservoir parameters,and the evaluation of reservoir quality and the identification of fluid properties.Statistics and statistical analysis of rock characteristics,such as rock composition and experimental data of mercury pressure,are statistically analyzed that the lithologic change are large,and the composition and the pore structure are complex.The relationship between porosity,permeability,and lithology is not unique,and the range of permeability is great under the same porosity;the reservoir decreases with the increase of cement content,especially with the increase of carbonate content decreased obviously;Oil bearing is good for the better reservoir physical properties;it shows worse for poor physical property.The complex lithology,physical property,and water nature cannot reflect the oil-bearing property of the reservoir wells.The large size of rock size,the content of high carbonate rock and the muddy interlayer are the main controlling factors that lead to the complex electrical characteristics of the low porosity and low permeability reservoir.In addition to the influence of high bound water saturation and thin sand shale interbeds,the main control factors of carbonate content difference are more obvious.Because of hydrocarbon emplacement early dissolution of carbonate minerals,advanced carbonate mineral deposit,and diagenesis by rock,carbonate minerals in the water accumulation makes porosity further reduce,the pore structure is more complex,resulting in aquifer resistivity uplift,the oil,and water resistivity contrast reduction.Using acoustic slowness and density curves to characterize two key factors of rock skeleton structure and skeleton volume,we realized the identification of sandstone skeleton particle size and sandstone lithology,providing the research foundation for facies controlled oil-bearing identification.Based on lithology discrimination,the oil-bearing identification chart from resistivity and slowness data is established.When the lithology of the block is relatively single and there is a small change,oil-bearing identification chart from the resistivity and natural gamma logging data is established through the relative value of natural gamma which can reflected the small continuous change of lithology.When the difference of carbonate content is regarded as the main controlling factors of oil and gas characteristics,we established identification chart of the apparent formation water resistivity and carbonate mineral content.Multiple regression and porosity element models are established from acoustic-and density-logging data,the average absolute error of which is less than 2%.Combined the core analysis,the permeability calculation model based on pore structure division and rock particle size clustering is established,which improves the accuracy of the permeability calculation in the target area.Base on m,n parameter method combined with regional water analysis data and formation water resistivity from logging data,the average absolute error of oil saturation model is less than 5%.The optimal nuclear magnetic component,pore structure index,and coefficient of mercury injection parameters are regarded as reservoir quality factor.Based on the correlation between quality factor and logging information,we established the models of pore structure index and mercury injection,respectively,implemented a continuous curve of reservoir quality index,and established the quality evaluation chart and standard based on the core experiment.