Laboratory Experiment And Performance Study Of Fracturing Fluid With Calcium Chloride

It’s very dangerous for fracturing operation for a block of A oilfield in western China with the depth more than 8000m,the formation pressure close to 140MPa and the maximum temperature close to 190℃.This paper established a weighted fracturing fluid system with controllable cross-linking time,good temperature resistance and shear resistance.Firstly,an experimental platform including rheological test,gel breaking test,core damage experiments and surface tension test was established,and theinstruments,experimental steps and reagents for each experiment were given.The temperature resistance and shear resistance of the fracturing fluid,the breaking property,surface tension,residue and damage property were measured by experiments.Secondly,calcium chloride was selected as the weighting agent,and the concentration was determined to be 35%and the weighting density was 1.35g/cm3.The preferred thickener was carboxymethyl hydroxypropyl guar gum and the gel breaker ammonium persulfate.The regulator JZ-2,crosslinking agent JZ-3,temperature stabilizer JZ-4,and cleanup additive JZ-5 were selected as a weighted fracturing fluid system.Finally,the performance of the calcium chloride weighted fracturing fluid system was evaluated to identify the factors affecting the performance of the fracturing fluid system and to determine the concentration of each additive:the concentration of regulator,temperature stabilizer and crosslinking agent was 0.2%,0.5%and 0.5%respectively.The formula of temperature resistant 140℃ and 150℃ increased fracturing fluid was formed and its performance was evaluated,the base fluid viscosity was lower than 110mPa-s,and after shearing two hours viscosity was greater than 100mPa·s.The gel breaking is downright and the viscosity is lower than 5mPa·S,and the damage rate to the reservoir is less than 20%.The low frictional resistance weighted f·racturing fluid system has been applied to A oilfield in western China to reduce wellhead pressure by 10%-20%and keep safety in fracturing operation.