Design Optimization for Water-Based Drilling Fluids in a Deepwater Gas Field on the Western Coast of Myanmar

In order to cope with the problems encountered in deepwater gas reservoir drilling on the west coast of Myanmar, such as borehole instability in water-sensitive shale formation, mud thickening at low temperature and high pressure on the seafloor, and the generation of natural gas hydrate, strong inhibitory water-based drilling fluid HIDril was optimized and designed on the basis of optimizing drilling fluid rheology at low temperature and selecting key agents including a gas hydrate inhibitor, taking polyamine inhibitors SDJA as the key agent. Indoor performance evaluation results showed that the drilling fluid of lower viscosity, higher dynamic shear and 6 value was better for hole cleaning, and at the temperature 4℃, it had good rheology. The mud displayed satisfactory performances in inhibition of hydration of water sensitive mud shale and achieved the highest recovery rate of water-sensitive shale up to 96.33%. In the simulated seabed environment with low temperatures and high pressures, HIDril could effectively inhibit the formation of gas hydrate. Drilling fluid permeability recovery rate was above 85.57%, which had a good reservoir protection effect. On this basis, drilling fluid technology program was designed according to the characteristics of different well sections in the deepwater gas field at the west coast of Myanmar and the design results could provide reference cases for drilling activities in this deep water gas field.