Research On Comprehensive Technology Of Macro-channel Recognition In The Middle And Late Period Of Oilfield Development

After long-term water injection development in most domestic oilfields,the current water content of the main oil layers has reached more than 95%.The main reason is that there are advantageous channels for the flow of injected water in the rock formations.How to accurately identify these channels to reduce and avoid inefficient and ineffective displacement circulation has become a necessary task to improve the efficiency of oilfield extraction.Taking the Daqing Changyuan Sazhong block as an example,the paper summarizes and analyzes the geological regional characteristics and rock development status of the block,and points out that the main oil layer in the block has a comprehensive water cut of over 95%,and low-efficiency and ineffective displacement cycles are common.First of all,it can be seen from the scanning electron microscope pictures of the washed cores of the inspection wells that the injected water can easily carry away the fine particles in the high permeability zone of the rock formation,causing the high permeability zone to become a“macro-channel” for the unblocked injected water.Based on the seepage mechanism of injected water in the rock formation,the analysis gives the possibility of formation of macro-channels in different sedimentary rhythms(positive rhythm,anti-rhythm,compound rhythm and uniform formation),and points out that the bottom of positive rhythm reservoirs is easier to form macro-channels.Select rock samples with different permeability of the main oil layer,and conduct parallel core displacement experiments in accordance with the three combinations of higher-high-medium,high-medium-medium,and high-high-medium.Heterogeneity,uniform permeability and thickness are the main reasons for inefficient and ineffective circulation.Secondly,the dynamic test data can be used to judge whether there are macro-channels and the direction of macro-channels in the rock formation.According to the study of the dynamic data in the study area,it is found that when there is a“macro-channel” with unobstructed injection water in the rock formation,the injection water absorption profile given by the tracer logging shows an abnormally high value,and combine with the potential abnormal position of the interwell potential,it can be inferred in advance the direction of the dominant channel of injected water.At the same time,when inefficient circulation of macro-channels occurs,the balance of injection-production pressure in the rock formation is destroyed,showing a phenomenon that the test pressure of the rock formation drops and the speed is fast.Third,establish a comprehensive identification standard for macro-channels based on static and dynamic data in the study area,and form a recognition process to achieve effective prediction of the location and direction of macro-channels.On the basis of summarizing and analyzing the inefficient circulation treatment effects of “macro-channels” in each well area,it is pointed out that blocking macro-channels,sub-layer water injection technology,unstable water injection methods and periodic water injection technologies are the current effective measures to control the low efficiency of macro-channels.