An experimental study on examining the outcome of including surfactant to cement spacer design on mud removal efficiency and bonding of cement with formation

Effective spacer design is a key factor in cement's ability to produce a strong bond between the cement-casing and the cement-formation. Mud displacement, mud cake removal, and cement contamination with drilling mud are the different applications of the spacer. Furthermore applications include changing the wettability of the formation and casing, particularly when drilling is carried out with oil-based mud and the production zone is expected to be oil-wet. Oil wet formations can limit cement bonding with the formation, resulting in pressure transmission between hydraulic fracture stages and lack of zonal isolation. This paper investigates how adding surfactants to cement spacer design affects cement bond performance under reservoir temperatures, where the surfactants will help to mitigate the impact of oil base mud on cement performance, reduce drilling mud compatibility issues, change formation – casing wettability from oil-wet to water-wet, and reduce interfacial tension (IFT) between the mud and the cement. The investigation was conducted using Wolfcamp core samples. To simulate the oil well, the core samples were chopped into small pieces and aged in oil-based mud (8.8 ppg and 12.5 ppg) at reservoir temperature for 10 days. The wettability of the chip was then determined using the captive bubble method. The chips were then submerged in a spacer mixture. The experiment was carried out using three different surfactants (Anionic, Nonionic, and Zwitterionic surfactant). The wettability of the chips was tested again after they were exposed to the aforementioned spacers to see how surfactants affected the wettability. The interfacial tension (IFT) between the spacer and the crude oil was also measured. To investigate the mixability issue caused by the presence of surfactants in the spacer design, oil-based mud and spacer compatibility tests were done. In addition, beaker and rotor cleaning experiments were used to assess the efficacy of various surfactants in removing mud.