Research On The Preparation Of High-density Solid-free Kill Fluid By Using Salt-extracted Waste Brine

The well killing fluid is a kind of liquid used to balance the formation pressure in the completion operations such as Perforating wells,testing oil,mending operations.Currently,manufacturing the high-density and solid-free well killing fluid is expensive while Sichuan is rich in brine resources and salt industry is well developed.A vast number of waste brines will brought by extracting salt and they include kinds of inorganic salts such as CaCl2 which dengsity can reach to 1.2g/cm3.So it can be used to make low-cost,good performance of high-density and solid-free well killing fluid.In this way not only can achieve the reuse of waste,but also can contribute to the development and production of oil and gas.The three different salt waste brines were tested through ion concentration testing,density testing,single aggravating experiment.pH measurement and then determine to use the ordinary calcium old water as the base fluid.Also,according to the characteristics of the waste,choosing the zinc chloride,zinc bromide,calcium bromide three kinds of inorganic complex system as the well killing fluid heavier weighting agents,and adding other well killing fluid additives to prepare 1.6g/cm3,1.7g/cm,1.8g/cm3 three different high-density solid-free well killing fluid.Three different densities of high-density solid-free well killing fluid were measured by viscosity test,water loss measurement,the rate of core damage test,the compatibility with the crude oil as well as the formation water,the stability performance testing at high temperature with high pressure and to determine the best material composition of three high-density solid-free well killing fluid and optimize the fomula of each part in high-density solid-free well killing fluid.The mass fraction of the components in the well killing fluid were as follows.The density of 1.6g/cm3 ordinary calcium old water was 70.6%.zinc chloride was 21.1%,zinc bromide was 2.65%,calcium bromide was 2.65%,xanthan gum was 0.2%,fluid loss additive(NT2)was 0.6%,clay stabilizer TL-1 was 0.4%,stabilizer(HEDP)was 0.2%.The density of 1.7g/cm3:ordinary calcium old water was 66%,zinc chloride was 22.8%,zinc bromide was 6.5%,calcium bromide was 3.3%,xanthan gum was 0.2%,fluid loss additive(NT2)was 0.6%,clay stabilizer TL-1 was 0.4%,stabilizer(HEDP)was 0.2%.The density of 1.8%/cm3:ordinary calcium old water was 58.5%.zinc chloride was 24.1%,zinc bromide was 12%,calcium bromide was 4%,xanthan gum was 0.2%,fluid loss additive(NT2)was 0.6%,clay stabilizer TL-1 was 0.4%,stabilizer(HEDP)was 0.2%.In order to reduce the corrosion of the the high-density solid-free well killing fluid made by the waste brine,a corrosion inhibitor is synthesized by orthogonal experiment,which use the diethanolamine,formaldehyde and acetophenone as the raw materials.The performance of the inhibitor is researched by utilizing weight loss method,electrochemical method and SEM method to observe the inhibition effect of the inhibitor on N80 and P110 steel in the well killing fluid.The result have shown that the optimal reaction condition is that:the molar ratio of the reactant(diethanolamine:formaldehyde:acetophenone)is 1.2:2:1.2,reaction temperature is 110? reaction time is 10h,reaction pH is 1,and that the best concentration of the inhibitor is 80 mg/L.In the temperature range of 60-80? with the same concentration,the inhibition efficiency of the N80 is from 87.07%to 93.12%and the inhibition efficiency of the P110 is from 88.05%to 92.62%,and that the efficiency of the N80 reach especially at 93.12%,92.42%and 90.86%,and the efficiency of the P110 reach especially at 92.61%,92.47%and 90.78%when the well killing fluid is of the density of 1.6g/cm3,1.7g/cm3,1.8g/cm3 with the inhibitor concentration of 80 mg/L.A complete protection film is formed on the surface of the metal matrix when the inhibitor adding in the well killing fluid,and the corrosion electric current is reduced from 1O-4 A/cm2 to 10-5A/cm2,so the corrosion of ordinary steel is reduced in the well killing fluid.Also after adding the inhibitor in the well killng fluid,the corrosion of the killing fluid is absolutely slower in the environment of high temperature and pressure and the corrosion of high-density solid-free well killing fluid on N80 steel corrosion is less than P110 steel.Through the above mentioned study can further show that utilizing waste salt brine can produce good performance,low cost,high-density solid-free well killing fluid which can be widely used in oil field operations.