During drilling process, The two main types of mud are WBM drilling system and OBM drilling system.
It generally used in vertical drilling and shallow drilling, WBM drilling system generally includes 3 kinds: one is the combination of water and drilling cuttings debris plugging agent;The second is the slurry of industrial salt;The third kind of water-based mud mixed by polymerizing agent;
Water-based mud drilling cost is relatively low, which is the current mainstream drilling mud system.
Water-based drilling fluid has the advantages of low cost, simple configuration , treatment and maintenance, wide source of treatment agent, multiple types of choice, easy to control performance, and has a good effect of protecting oil and gas reservoir. Therefore, it is a common drilling fluid system for drilling oil and gas reservoir both here in China and internationally.
But the disadvantage is that water-based mud in the paste salt layer and mudstone layer is easy to cause water absorption expansion, resulting in well wall collapse.
Water- based mud drilling system
Oil-based mud drilling is mainly used in directional Wells and ultra-deep Wells.
There are two types of oil-based mud, one is to inject diesel into the mud to become oil-based mud;Another is to mix bitumen into oil-based mud;
In general, two mud systems are required on the drilling site, water-based mud for the first half and oil-based mud for the second half.
Oil-based mud, is a water-in-oil emulsion drilling fluid consisting of oil as a continuous phase, water content up to 50% by volume as a dispersing phase, emulsifier as a stabilizer, and drilling fluid usually composed of diesel oil, oxidized bitumen, organic acids, alkalis, and other chemical agents.
Compared with the water-based drilling fluid, the oil-based drilling fluid has the advantages of high temperature resistance, salt and calcium resistance, conducive to well wall stability, good lubrication and less damage to the oil and gas reservoir.
At present, OBM drilling system has been developed into an important means of drilling high difficulty Wells ,such as high temperature Wells, deep Wells and various complex formation.But the preparation cost is much higher than that of water-based drilling fluid.
Oil- based mud drilling system
MECO oxidized bitumen is amphiphilic, it not only can be used in water-based drilling fluid, which to increase the lubrication of the filter cake and have an anti-sticking effect, plug the filter cake pore and adjust the bond force between the solid phase particles in the filter cake, reduce the filtration loss and prevent collapse.But also can be used in oil-based drilling fluid, as a viscosity-increasing agent, fluid loss control agent and suspension stabilizer in oil-based drilling fluids, and is also an important component of oil-based de-blocking agents.
