Preparation Methods And Performance Evaluation Of Foam Workover Fluid With Resistancing Heat And Salt Properties

Well workover is to rescind faults and improve borehole conditions which is helpful for the recovery of normal production of oil and gas wells.In the workover operations of low-pressure oil and gas wells,workover fluid leakage phenomenon often occurs due to pressure coefficient generally less than 1.0,leading to slow recovery or even irreparability of well productivity.Workover fluid performance will directly affect the degree of damage and the production level of oil and gas wells.Therefore,to improve the success rate of workover and control leakage,the research of low density workover fluids with excellent performance has becomed the top priority.Based on the the theory of surfactant,foam performance for ten different kinds of surfactants including SDS,BS-12 and so on were studied,finding that Anionic surfactants,amphoteric surfactants has better Foam performance.Through the binary match test of anionic/amphoteric surfactants,anionic/anionic surfactants and anionic/non-ionic surfactants,the match of SDS/BS-12 was found to have significant synergy.The Foam stability and stabilizing mechanism of foam for different foam stabilizers were studied and the research showed that foam stabilizer?XH-ZC-5?was more excellent to the foam stability than others and its stability mechanism was by raising viscosity and decreasing the permeability of the gas bubble surface.The best composition of ZYF-1 foam workover fluid system was determined: water + 0.5% SDS+0.5% BS-12 + 0.7% XH-ZC-5.Indoor experiment showed that temperature resistance of the workover fluid system was up to 150? and resistance to NaCl can amount to 20%,CaCl₂ can reach to 15%,oil pollution can amount to 15%.The workover fluid system can meet workover operation of deep Wells and ultra deep wells with high temperature and high salinity.The low-density of workover fluid and API filter loss of the workover fluid was less than 9.6mL,so the workover fluid can be used for low-pressure wells and high absorption wells.Meanwhile,the workover fluid has many excellent features such as low cost,non-solid,good fluidity,high viscosity and strong ability to carry sand and so on,and it is a non-Newtonian fluid with the power-law rheological model.