The reaction between the acid gases such as H2S and CO2 with the hydrational products of silicates results in serious corrosion to the set cement,which is manifested in the increase in the permeability and dramatic reduction in the compressive strength of the set cement,negatively affecting the integrity of the wellbore.To deal with this problem,a self-crosslinking epoxy resin emulsion is developed to improve the ability of oil well cement to resist the corrosion by H2S and CO2.In laboratory study,the performance and the mechanisms of set cement to resist corrosion are evaluated at H2S partial pressure of 2.0 MPa and H2S partial pressure of 1.5 MPa,and the results analyzed.The results of the study show that:1)Increase the concentration of the self-crosslinking epoxy resin,the compressive strength of the set cement increases;when the compressive strength of the set cement increases to a certain value,further increase in the concentration of the epoxy resin does not cause the compressive strength of the set cement to increase any more,it,on the contrary,causes the compressive strength of the set cement to decrease.The elastic modulus in this process decreases significantly.2)As the concentration of the self-crosslinking epoxy resin increases,the corrosion depth caused by the H2S and CO2 gases in the set cement and the permeability of the set cement decrease,the compressive strength of the set cement first increases and then decreases.3)The self-crosslinking epoxy resin can wrap up the hydrational products of the set cement,thereby isolating the set cement from being contacted with the acid gases and thus improving the corrosion tolerance of the set cement against acid gases.4)Cement slurries treated with the self-crosslinking epoxy resin have good engineering properties,leading to reduced sensitivity of the thickening time of a cement slurry to the aging time of cement water,the concentration of the self-crosslinking epoxy resin as well as changes in temperature,and these make the technology easy to use in field operation.The anti-corrosion tough cement slurry has been used in the cementing of 6 wells,more than 90%of the well cementing job is classified as"excellent",and 99%of the well cementing job is classified as"qualified".From the study and the field operation it is concluded that the self-crosslinking epoxy resin emulsion fills and wraps up as a membrane the hydrational products of cement,rendering the set cement good anti-corrosion performance and toughness,and this makes the anti-corrosion tough cement very suitable for cementing wells drilled in the high sulfide content blocks in northeast Sichuan.
关键词
固井/环氧树脂/防腐/韧性/水泥浆/高含硫/自交联/川东北
Key words
Well cementing/Epoxy resin/Anti-corrosion/Toughness/Cement slurry/High sulfide content/Self-crosslinking/Northeast Sichuan
维普
万方数据