A formate-based fluid has been successfully used in many HPHT well operations since they introduced in field practice. They have many advantages when compared with conventional HPHT drilling fluids such as: minimal formation damage, maintenance of additive properties at high temperatures, reduced hydraulic flow resistance, low potential for differential sticking, etc. Formate-based fluids can be applied during deep slim hole drilling, shale drilling, and reservoir drilling, salt and gas hydrate formations drilling.

The laboratory research was carried out to determine composition of formate base drilling fluid. It was formulated using sodium and potassiumformate salts, KCL, starch and lime stone. Formate base mud is solid free system. So, mud cake is thin and resilient, it is conductive to improve cementing quality greatly. In these experiments, formate based drilling fluids containing two types of formate salt (NaF and KF) at different concentrations were tested by a Fan-50 viscometer.

Experiments show that the formate drilling system has good rheological property and strong inhibition ability. It shows that potassium formate improves the thermal stability of polymers. Formate based drilling fluid achieve sufficient mud weight around 77 pcf was selected for field trial in one of the exploratory wells. Formate based brineis a free-solid Water Base Mud (WBM) which maintains rheological stability at high temperature and minimizes drilling problems. This case study shows how Formate based mud enhanced the wellbore stability and reduced the testing time and cost. Based on the success fulfield test results, it is planned to drill other deep formation with Formate based fluids in future.