Experimental Study On Displacement Of Fracture-cave Reservoir Based On Reservoir Conditions

Deep carbonate fracture-cave reservoirs have huge reserves,which is the focus and difficulty of oil and gas exploration and development at present,and also the main field of oil and gas replacement in the future as well as with important research significance.At present,the understanding of the fluid flow laws of fracture-cave reservoir,especially the mechanism of oil displacement in caves units,is unclear,which has led to the unsatisfactory development effect of this kind of reservoir.The laboratory core displacement experiment is the main method to understand and study the law of seepage flow in fracture-cave reservoir.This type of experiment can reflect the fluid flow law in the reservoir,to provide a scientific basis for predicting the fluid production law of a single well,developing a development plan,and enhancing oil recovery.But at present,the traditional experimental conditions of fracture-cave reservoir,whether it is the characteristic of the single fracture-cave parameter,the connection relationship fracture-cave,the temperature or the pressure,are significantly different from the actual reservoir,which make it impossible to scientifically understand the true flow law of the fracture-cave reservoir through traditional experimental methods.Given the problems existing in the current fracture-cave reservoir experiments,this study carries out a new experimental method study of the fracture-cave reservoir,which also proposes a method for making the simulated core of fracture-cave reservoir with controllable parameters and a heterogeneous fracture-cave core holder for considering the gravity and multi-parameter monitoring as well as the oil-gas-water three-phase micro-automatic metering device and the method using liquid level differentiation.Besides,the water-drive/gas-drive flow experiment using fracture-cave core made by the new method is also carried out in this paper.The main research results are as follows:1)Proposes a method for making artificial fracture-cave cores by using paraffin to form fractured-cave units and shaping them by pouring cement.This method has many advantages.For example,it is simple to manufacture,and the caves are controlled in shape and connection,and the wall roughness and wettability are closer to real cores,and it’s suitable for high temperature and high-pressure experiments.It solves the difficulties of controlling the shape and the connection mode of the caves,and of the roughness and wettability of the wall that is very different from the actual reservoir,and of some artificial cores that cannot withstand the high pressure in a traditional method.2)Proposes cross-shaped multi-monitoring combined fractured-cave core holders,which can realize the combined fracture-cave core experiment with high-temperature and high-pressure,so that different fracture-cave units can directly contact and can control the relative height positions of different fracture-cave units.It can also realize the monitoring of multiple parameters(temperature,pressure,oil-water interface)in different branch fracture-cave units.The invention makes the connection relationship between different fracture-cave units more realistic,fully reflects the key role of gravity in the displacement process of fracture-cave reservoir,and solves the shortcoming of the conventional multi-holder experimental method of connecting different fracture-cave units with pipelines which have the disadvantage of displacement mechanism that is not in conformity with reality.3)Proposes the oil-gas-water three-phase micro-automatic metering device and the method based on liquid level differentiation.The device has a simple structure,convenient operation,high metering accuracy,good synchronization,and a high degree of automation.It solves the shortcomings of the difficulty to measure oil,gas,and water at the same time,and of the low degree of automation and calculation accuracy in the core flow experiment.4)Carries out the flow experiment of water-flooding before gas-flooding on the fracture-cave core produced by the new method,and studies the effects of fracture-cave occurrence,the filling degree of caves and the pressure on reservoir recovery.Generally speaking,the oil recovery of fracture-cave unit is higher between 75.29% and 85.57%.Study shows that fractures with the high fracture-cave occurrence,less cave filling,and low pressure have higher oil recovery.The thesis combines the results of fracture-cave displacement experiments with the experimental phenomena of visualizing single fractures and single cave experiments and discusses the influencing factors and methods of oil recovery of fractures and caves.The experimental method of fracture-cave reservoir displacement experiment proposed in this paper makes the experimental conditions closer to the actual reservoir conditions,which will provide a more scientific and accurate study of fluid seepage law of fracture-cave reservoirs.The results of the single fractured-cave unit experiment will also deepen people’s understanding of the oil displacement law of fracture-cave reservoir and provide a theoretical basis for the efficient development of such a reservoir.