Research into sulfide resistant polymer latex cement for sour well applications

Abstract

PurposeThe long‐term durability of cement becomes an important challenge in oil and gas wells due to the aggressive acid gas. H2S has been found in more and more wells. The purpose of this research was to add polymer latex to the Class G cement in order to promote the H2S corrosion resistance of oilwell cement.Design/methodology/approachThe water loss and thickening time of cement slurry and compressive strength and gas permeability of bond cement were investigated to determine the cement formulation. The corrosion resistance of the polymer cement was compared to base Class G cement in solution with 1.8 MPa H2S at 120°C.FindingsThe optimum concentration of polystyrene latex was determined as 5 percent. The permeability change, compressive strength loss and corrosion ratio of latex cement were all lower than for the base Class G cement. The electrochemical impedance spectroscopy results and microstructure details confirmed that the latex cement had stronger resistance to the aggressive medium. Thus, latex cement had excellent corrosion resistance to H2S.Originality/valueThe findings of this study can further improve the sulfide resistance of Class G cement. Two roles of the polystyrene latex were observed in the cement, including interstitial in‐filling of the pore structure and packing around hydration products, which are proposed to properly explain the results.