Application Of Low-cost Microfluidic Technology In Enhanced Oil Recovery

Enhanced Oil Recovery(EOR)is aiming to further improve oil recovery by using physical,chemical,and biological methods after secondary oil recovery.Natural cores are commonly used to conduct EOR experiments.However,this method has many drawbacks,such as complicated experimental process,difficulty in visualization,and inability to study the microscopic oil recovery process at the pore scale.Microfluidics is a technology that studies,processes,and controls fluids at the microscales or nanoscales.The microfluidic chip is a microdevice that manipulates and processes fluid on microscale.Using micro fluidic chips instead of natural cores to conduct displacement experiments in EOR study,could scale down the whole system setup to a few square centimeters in size,which provides a new tool for researchers in the energy field.In this dissertation,the low-cost microfluidic technology was applied to the study of EOR related research for the first time to the best of our knowledge.The key problems in the application of low-cost microfluidic technology in EOR related research,including chip structure design,chip manufacturing technology,microfluidic experimental platform construction,and experimental research methods,were studied.Based on the low-cost microfluidic technology,the experimental and mechanism study of EOR technology at the pore scale were realized.This study greatly reduces the cost and technical threshold of microfluidic technology in EOR related research,and provides a new way for the application of microfluidic chips in petrochemical and energy fields.The contents of this study are as follows:(1)Structure design and finite element simulation of the microfluidic chip structure for EOR research.Microfluidic structures used in EOR research are generally classified into four main categories based on the geometry and topology:regular structure,partially regular structure,irregular structure,and natural reservoir structure.These structures are usually designed only for a single experiment and lack unified design standards and connections,which makes it difficult to objectively compare their performance and application occasions.This dissertation presents a chip structure design method based on natural reservoir slicing.The simulated natural reservoir structure and the corresponding pore structure parameters were extracted from the natural reservoir slices.Based on the parameters,the design methods of regular structure and partially regular structure are proposed.The pore structure parameters of the three structures are highly consistent.Then,the influence of three chip structures with similar pore parameters on the oil displacement process was analyzed through finite element simulation,which allows an objective comparison of the performance of the three types of structure.The results provide a reference for the design and selection of chip structure.(2)Research on low-cost microfluidic chip processing technologyTo reduce the high dependence of traditional microfluidic chip processing on precision equipment,ultra-clean environment,and complex technology.This dissertation studies the processing technology of microfluidic chips based on low-cost microfluidic technology.The chip processing technology based on thermoplastic polymer and natural minerals were first proposed.The chip bonding technology for a variety of materials was also studied.The effects of process parameters on the size,morphology,surface properties,and bonding effect of the microstructures were analyzed.In this dissertation,the processing technology of microfluidic chips based on low-cost microfluidic technology was studied.With this method,a microchannel with depth and width range of 50-500?m can be processed.This enables the simulation of the natural reservoir in terms of both microstructure and surface properties.Low-cost flexible preparation of microfluidic chips can be realized in a non-ultra-clean environment,which greatly reduces the cost of microfluidic chips and the requirements for precision equipment and processing environment.(3)Design of the microfluidic experimental platformTo better apply the microfluidic chip to EOR related research,this study designs the microfluidic experimental platform from three aspects:fluid drive,flooding process control,and visualization based on the optical method.The designed experimental platform meets the requirements of related research on the multi-fluid injection,multi-phase flow non-interference sequential injection,multi-scale visualization,and real-time recovery analysis,which provides a stable and reliable experimental platform for subsequent experimental research.(4)Experimental and mechanism study of EOR based on a low-cost microfluidic systemA series of EOR experiments and mechanism studies on water flooding,thermal flooding,surfactant flooding,and microbial flooding were carried out based on the designed microfluidic platform.The real-time visualization of the oil recovery process was realized.The enhancement effect and mechanism of different EOR technologies on recovery rates were studied from two scales of the whole chip and single pore.The results verified the effectiveness,stability,and advancement of the low-cost microfluidic system proposed in this dissertation,and provided the experimental basis for its further application in the energy field.