A Study Of Fracturing Technology On Ultra-High Temperature Deep Reservoir

In recent years, with the growing demand and improvement of exploration technology, the exploratory development of hydrocarbon resources further develop in depth. More and more main exploration targets have the overall trend of sinking, the well depth is more than 4500m, the number of the abnormal high temperature deep wells which are more than 170℃is increasing. As the most effective stimulation for this type of reservoir, fracturing has got comprehensive attention both here and abroad. But the high temperature and high pressure of the deep layer bring more difficulty to the improvement of reservoir. High temperature fracture fluid(more than 180℃), the discrepancy of fracturing design philosophy and technology, the scale optimization of big-frac treatment constraint the exploratory development of this reservoir. This paper study some key theory and technology on abnormal high temperature deep reservoir, the main results are as follows:1.On the basis of analysing the formulation characteristics and performance indicators of the ultra-high temperature fracturing fluid abroad, we develop the agent of ultra-high temperature fracturing fluid, finish the experiment comprehensive evaluation, develop the low damage fracturing fluid system which is suitable for ultra-high temperature reservoir fracturing and fracturing fluid which could be used in the case of 190℃.(1) Under the conditions of 0.1 %～0.6% cross linking ratio, the cross linking speed and the viscosity will increase after the temperature of the high temperature fracturing fluid sample rising to 40～50℃. As the temperature reach 120℃, the viscosity will increase significantly and show the viscosity-temperature characteristic which is in contrast with the conventional fracturing fluid system in the medium temperature zone.(2) The result of HAAKE RS600 theological test shows that, the rage of the best cross liking ratio of the ultra-high temperature fracturing fluid is 0.2%～0.3%.(3) The result of the 180～200℃fracturing fluid viscosity-temperature experiment shows that the viscosity of the 0.55% GHPG is 164.5mPa.s and the viscosity of the 0.60%GHPG is 332.8 mPa.s when the temperature is 180℃.(4) The result of the 180～200℃fracturing fluid viscosity-time experiment shows that in the best cross linking ratio the viscosity remains at 90～100mPa.s after 120 min 180℃,170s-1 continuous shearing, the viscosity remains at 70～80mPa.s after 120 min 190℃,170s-1 continuous shearing and the viscosity remains at 60～90mPa.s after 120 min 198℃,170s-1 continuous shearing. The fluid have excellent heat-resisting property and shear performance which meet the requirements of the sand fracturing for the ultra-high temperature deep reservoir.(5) The ultra-high temperature fracturing fluid jel under the action of 180℃, 50ppm breaker, the viscosity will reduce to 20mPa.s after 50min shearing and the viscosity will reduce to 10mPa.s after 70min shearing.(6) The serface tension of breaker is 28.4mN/m, the solid residue is 587mg/L, the content of the residue is a little more than common fracturing fluid.2.The delay cross linking experiment shows that, the first inflection point of the GHPG gel viscosity is about 4 min, the system is partial cross linking and it has linear structure, strong liquidity and low friction. The second inflection point is about 8～10min, the system is reticulation and the viscoelasticity is high.3.The result of the LOOP circulation friction experiment shows that under the conditions of 80℃, 76mm operating tool string and 4～6m3/min discharge capacity, compare the friction of ultra-high temperature fracture fluid with the friction of clear water, the drag reduction rate of the former is 30%～40%.4.When the shut-in pressure is under 20.7～82.7Mpa the damage rate of breaker to fracture is less than 20%.5.Finish optimum the amount of breaker desigh for the ultra-high temperature fracturing on the basis of wellbore temperature field and fracturing temperature field calculation model.6.According to the well-log information, rock mechanics experimental parameter and actural construction data, we get longitudinal stress profile of Fengshen block, establish the breakdown pressure of ultra-deep reservoir prediction method and the surface pressure prediction model.7.Establish the proppant return mechanical model in the flowback of fracturing fluid and critical flow-back model after the closing of fracture, realize quantifying the fracturing flowback parameter and choose the best blowout choke size and present the control technique for proppant return.