Optimization And Evaluation Research Of Non-water Energy-increased Carbon Dioxide Fracturing Fluid System

Fracturing is one of the major effective methods for reservoir reconstruction.The conventional hydraulic fracturing technology has the advantages of easy preparation,high liquid efficiency,relatively low cost,etc.The disadvantages are higher harm and less easy to return.Compared with conventional hydraulic fracturing technology,carbon dioxide fracturing technology adopts liquid carbon dioxide as fracturing fluid,which has the advantages of no aqueous phase,high flowback,little damage to reservoir and large increase range in production.In this paper,rheological behavior,friction characteristic and suspended sand characteristic of carbon dioxide fracturing fluid have been evaluated by rheological test,friction test and suspended sand test.The copolymer of styrene fluorinated acrylic is used as CO₂ tackifier,and it is made into CO₂ fracturing fluid.It has studied on different tackifier contents,different temperature and pressure on the impact of carbon dioxide fracturing fluid viscosity.With the increase of tackifier content,the viscosity of CO₂ fracturing fluid increases gradually,and the viscosity of liquid CO₂ decreases with the increase of temperature,and increases with the increase of pressure.When the temperature is-10?and the pressure is 10MPa,the viscosity of pure liquid CO₂ is 0.133mPa·s,and the viscosity increases to 8.92 mPa·s after adding 2wt%tackifier,and the effect of lifting is obvious;Then researched the effect of different temperature and different pressure on friction characteristic of pure carbon dioxide fracturing fluid,when the pressure is the same,the higher the temperature is,the smaller the friction pressure gradient of liquid CO₂ is.When the temperature is the same,the higher the pressure is,the greater the friction pressuredrop;Finally,the settling velocity of proppant particles in different CO₂ fracturing fluid systems was measured by visual reaction kettle.When the temperature is-10?,the pressure is 20MPa,the settling velocity of proppant in the pure liquid CO₂ is 16.52m/s,adding 2wt%tackifier proppant settling velocity is 10.34m/s,then add 1.5%fiber after sedimentation rate is 8.41m/s.The increase of viscosity of the fracturing fluid and the addition of fibers can reduce the settling velocity of proppant particles.