| The fracture-cavity reservoirs are characterized by high heterogeneity,complex oil-water relationships,and a variety of structures and sizes of fracture-holes,creating great difficulties for development.At present,TH oil field mainly use flood development.However,at the later stage of development,poor development of water injection effect.Continuing water injection will only lead to continuous uplift of the oil and water interface,which will increase production well water out and "garret oil" on the wellbore area can not be produced.Therefore,only the flood development method will not meet the development needs.A large number of studies have shown that the development method of gas injection can effectively solve the problem of water production in the later stage of reservoir development,and can further improve the recovery ratio.Based on the two kinds of oil samples and on-site test data provided by HT oil field,this article carried out experiments of gas injection and expansion of high-temperature and high-pressure crude oil,gas-oil diffusion experiments in fracture-cavity reservoirs,N2 injection and displacement of crude oil experiments in fracture-cavity reservoirs,experiments on the gas migration rule of crude oil in the glass cylinder and established the calculation model for the rising velocity and final velocity of bubbles in the fluid.At the same time reached the following conclusions and understanding:(1)Set up an experimental test device for measuring the vertical migration velocity of reservoir gas in simulated fracture-cavity reservoirs(Organic glass:0.15m×0.15m×0.30m).The system evaluates two different crude oil gas migration rates(T702b well crude oil is 21.60mPa·s,T7-607 crude oil 11.86 mPa·s).The experimental results show that the rising speeds of bubbles in the two kinds of crude oil are 0.342?0.532m/s and 0.466?0.608m/s respectively.The rising speed and final velocity of the bubble calculation model show that the rising speeds of bubbles in the two kinds of crude oil are 0.396?0.507 m/s respectively.0.491?0.627m/s.The rising speed of bubbles decreases with increasing solution viscosity.In the process of rising bubbles,the shape of bubbles gradually changes from spherical,long spherical,and ellipsoidal to spherical cap shape.(2)In the gas injection expansion experiment,as the gas injection volume increases,the density of the degassed crude oil and the content of C7+ components increase,indicating that the injected gas extracts the light components in the crude oil.After injecting N2,both the volume of the formation crude oil in the two wells slightly expanded and the viscosity of the crude oil slightly decreased,indicating that the two wells injected N2,the effect of expansion and viscosity reduction was not good,and no obvious effect of improving the physical properties of crude oil was achieved.The type of reservoir injection N2 is mainly for the purpose of maintaining pressure.(3)Simulate the gas-oil diffusion process in the fracture-cavity storage group,and carry out experiments on the N2-oil diffusion of two different types of crude oil(oil from the T702b well and crude oil from the T7-607 well)under high temperature and high pressure conditions.The measured diffusion coefficients of N2 in the crude oil of T702b well and in the crude oil of T7-607 were 2.32×10-11 m2/s and 2.44×10-11 m2/s.The diffusion equilibrium time was 92h and 89.5h.(4)In the later stage of flood development,the N2 exploitation method was selected for the single-hole fractured-cavity model of the unfilled core,and the recovery ratio was increased by 50.3%,and the final recovery efficiency was as high as 99.17%.The T702b and T7-607 wells filled with a single-hole fractured-cavity model filled with a real core were selected for gas extraction in the late stage of flood development,and the recovery ratio was increased by 34.5%and 36.68%.It shows that the fracture-cavity type reservoir can be used for oil recovery in the later stage of flood development,which can further increase crude oil recovery ratio In contrast,the single-hole fracture model with unfilled cores has better gas injection development. |
PDF Full Text Request