Study On The Gas Flow Characteristics In Shale Reservoirs

With the reduction of conventional oil and gas resources,the exploitation of unconventional oil and gas reservoirs has attracted much attention.Shale,as source rock and reservoir,plays an important role in global oil and gas production.Shale has extremely low porosity and permeability,with nanopore systems,which greatly affects the fluid flow and gas diffusion in shale reservoirs.Therefore,studying on the gas flow characteristics in shale reservoirs has an important guiding significance for the development of shale gas.Based on the investigation of domestic and foreign research on gas flow characteristics of shale reservoirs,I studied the micropore features of shale reservoirs from qualitative and quantitative analysis.By constructing fluid flow experiments and combining with the micro-numerical simulation method,the fluid flow characteristics were studied and the influencing factors of permeability were analyzed.At the same time,the mathematical model of fluid flow in shale formation was established,and macroscopic numerical simulation of shale reservoirs was performed.In this paper,the following tasks have been mainly completed:(1)By constructing environmental scanning electron microscopy,nitrogen adsorption,high-pressure mercury intrusion,and nuclear magnetic resonance experiments,the micropore structure characteristics of shale reservoirs were qualitatively and quantitatively analyzed and the pore structure size was analyzed at a full scale.(2)By constructing fluid flow experiments,the single-phase and two-phase fluid flow characteristics were studied separately.The independently developed pulsed nonsteady-state percolation experimental test method can effectively measure the permeability of shale rocks.From a microscopic perspective,the change of fluid flow pattern of gas-water in nanotube bundles was observed.(3)The finite element numerical simulation software was used to simulate the flow of single-phase(gas)and two-phase(gas and water)fluid in shale reservoirs.The gas flow in shale reservoirs was mainly affected by the pore size,pore throat ratio,and coordination number.Knudsen numbers reflect the change of fluid flow from transitional flow to free molecular flow.The flow of two-phase fluid(gas and water)is affected by the wetting contact angle.(4)Based on the MRST module and MATLAB programming,macro-scale numerical simulation of shale gas reservoirs was performed.The effect of different fracture parameters on the production of shale gas reservoirs was analyzed.Under different fracture numbers,different fracture lengths,different fracture conductivity,and different fracture patterns,the sizes of daily gas production and cumulative gas production were analyzed.The research results of this paper will be helpful to understand the fluid flow mechanism in shale reservoirs and provide theoretical guidance for the exploitation of shale gas reservoirs.