The Additives Impact the Gel Strength of the Water Based Drilling Mud

Abstract

One of the most important functions of drilling mud is its ability to suspend the rock cuttings during drilling cease, this ability is related mainly to gel strength. Gel strength is caused by the attractive forces between the active particles of bentonite (clay) during the static period. Sodium-based bentonite concentration has a direct effect on the gel strength. In addition, cement contaminants may encounter drilling mud as a result of casing string cementation which in turn also leads to a noticeable impact on gel strength. As consequence, it is vital to observe drilling mud gel strength continuously to identify efficient drilling mud functions. In this paper, an experimental study was performed via a shearometer, the aim of this study is to investigate the effect of the variety of the weights of sodium-based bentonite and cement slurries on the gel strength of water based mud. To analyze the influence of bentonite additives, four drilling mud samples were prepared with bentonite weights; 40, 60, 70, and 80 gm respectively, and gel strength was measured at each weight. While cement contamination had been examined by preparing three drilling mud samples contaminated with 2 gm, 3 gm, and 5 gm of class G cement. The results showed that an increase in bentonite quantities leads to rising in gel strength directly. The findings also showed that gel strength increased as the level of cement slurries raised. Furtherer increase appeared from 20.2 to 42 lb/100 ft² when cement weight increased from 2 to 5 gm respectively.