Calibration And Evaluation Of Acoustic Imaging Of Fractured Reservoirs In Oil-based Mud Sandstone

With the development of the oil and gas industry,high-porosity and high-permeability monolithic sandstone reservoirs have been difficult to find,and major oilfield companies have to turn their attention to the exploration and development of complex lithologic reservoirs such as low-porosity and low-permeability fractured sandstones.Tight-fracture reservoirs are one of the important areas for oil production and storage in the 21 st century.The results of oil and gas exploration for many years show that the middle and high-production intervals in the dense sandstone reservoirs are generally the relative development intervals of the fractures,and the exploration of oil and gas reserves is gradually increasing.The fracture is not only an important reservoir space,but it also provides an excellent fluid percolation channel that allows isolated pores to communicate,develop into an effective reservoir space,and greatly increase matrix permeability,so the fracture determines the tight sandstone storage.The key factor of layer production capacity.Therefore,the identification and evaluation of fractures in tight sandstone reservoirs is of great significance for the targeted and efficient development of such reservoirs.In the study of fractures,core analysis and imaging logging are the main method techniques.The core can provide the most realistic information of the fractures.However,since the length of the coring is short and incomplete,it is easy to use the core analysis to study the fractures."Full";imaging logging can achieve the evaluation of fractures in the entire target interval,but due to the influence of resolution and induced joints,natural fractures cannot be picked accurately,so the results obtained have large errors.Therefore,we need to use the core fracture parameters to scale the imaging fracture parameters,so as to improve the accuracy of the imaging logging fracture parameters to make it more realistic.For water-based mud electro-imaging,the qualitative identification and quantitative evaluation system of fractures develops rapidly and tends to be perfect.In oil-based mud tight sandstone fractured reservoirs,due to the poor conductivity of oil-based mud,the difference in resistivity between effective pore segments and skeleton The value is not large,resulting in poor electrical imaging and missing geological information in the well.In addition,the use of oil-based mud not only changes the absolute value of reservoir resistivity,but also the intrusion characteristics change the relationship between deep and shallow resistivity,and the geological structure artifacts are easily formed on the imaging pattern,which brings huge identification and evaluation of fractures.Difficulties.Acoustic amplitude attenuation is closely related to the degree of fracture development and is less affected by mud resistivity.It provides a possibility for ultrasonic imaging logging technology to evaluate the effectiveness of fractures.However,due to the fact that the ultrasonic imaging fracture analysis software is not yet perfect,the core fracture parameters are used to scale the ultrasound.The research results of imaging fracture parameters are very scarce,resulting in low utilization rate of ultrasonic imaging logs in oil-based mud wells.How to effectively use ultrasonic imaging data to evaluate fractured sandstone reservoirs has become the focus of current research.Based on the logging data of oil-based mud wells in Keshen area,this paper analyzes and explores the method of quantitative calibration of ultrasonic imaging fractures.Firstly,the core fracture parameters are obtained by the above core observation and description method,and the natural gamma value of the core ground is utilized.The core depth is homing to the uniform depth scale of the conventional GR curve;then the imaging raw data is processed in the imaging logging software to obtain the fracture face rate and other parameters in the image,and then the fracture face rate is processed by the curve calibration function.It is also homing to the uniform depth scale of the conventional GR curve.Finally,the relationship between the core face fracture rate and the imaging face rate obtained by imaging processing is analyzed,and the relationship between the two is obtained,and the scale coefficient between the two is obtained.Rate scales the purpose of imaging face rates.Finally,a method for imaging the crack face rate using the core fracture face rate scale is summarized.Using this scale method,the accuracy of ultrasonic imaging logging fracture evaluation can be improved,so that the ultrasonic imaging logging data of oil-based mud well can be effectively utilized,and good application results are obtained in the actual well fracture evaluation.