Study on sodium fatty alcohol polyoxyethyleneether sulfate relieve the contamination of oil well cement with mineral oil-based drilling fluids

•Mineral oil-based drilling fluids (MOBM) have a large negative impact on the structure and properties of the oil well cement, this phenomenon is called “contamination”.•AES can effectively relieve the contamination.•The mechanism of the contamination is that the effects of both osmotic pressure and demulsification change the free water and oil phase hinders the hydration process.•The mechanism that AES relieve contamination is adsorption and breaking the emulsions. Contamination of oil well cement slurries with mineral oil-based drilling fluids (MOBM) is considered to be a great challenge for cementing security and quality. In this paper, a surfactant of sodium fatty alcohol polyoxyethyleneether sulfate (AES) relieve the contamination of oil well cement with MOBM was investigated. The cement slurries containing different MOBM and AES contents were prepared according to API Recommended Practice for testing oil well cements 10B-2 and rheological properties, compressive strength, porosity, gas permeability, Freeze-drying/Environment Scanning electron microscopy (ESEM), X-ray diffraction (XRD) were tested. The results indicate that the presence of MOBM in cement slurries resulted in a serious contamination (compressive strength and rheological properties decrease, porosity and gas permeability increase). On the other hand, above-mentioned properties increase with the addition of AES in contaminated cement slurries. The reason may be is that the added AES can damage the water-in-oil emulsification structure of contaminated cement slurries and improve the hydration of cement particles. In addition, this study provides a method to relieve the contamination and explores the mechanism of contamination to find the possibility of further measures.