DRILLING FLUIDS SYSTEMS
Drilling fluids helps in performing essential functions during the construction of oil wells especially while transporting cuttings to the earth’s surface. Drilling fluids also help in preventing some well-control issues, reducing formation damage, wellbore stability, lubricating and cooling the drill string, and also providing information about the wellbore.
All these functions by drilling fluids are extremely important and add to the overall success of a well rig construction.
Drilling fluid systems have a liquid continuous phase and a discontinuous phase involving solids. Sometimes, they also consist of a gas phase that is caused by design or by the formation of gas entrainment.
Design and maintenance of drilling fluids are iterative and are affected by surface and downhole conditions. The deeper the drilling goes, the more the conditions change, encountering a constant change in temperature and pressure. There are different types of rocks and formation fluids that change the mud as it travels.
There are three main phases for drilling design and maintenance.
During the planning phase, fluid experts would have to select from an array of mud system types and designs for each section. These systems are designed with different specifications such as thermal gradients, environmental concerns, and borehole stability. Water is usually the first fluid used for drilling but as the borehole deepens, the pressure increases, as well as the temperature and these, would require more complex fluids.
The character of drilling fluids constantly changes, going through energy consumption, lifting cuttings, cooling bits of cuttings, and finally releasing waste to the surface. All of these are reasons why fluid engineers and specialists ensure they constantly evaluate and recharge the system with fresh fluids.
Measurement and Redesign
Returned mud is no longer ordinary mud and drilling fluids specialists have to measure the properties of this returned mud. Some properties include rheology, phase content, density, filtration rate, solids content, and classification. It is also analyzed for alkalinity, pH, acid-gas content, hardness, and others. Based on the results, a fluid specialist then designs a treatment program for the next 24 hours. A lot of monitoring goes into well drilling.
The technology and science of drilling fluids have evolved exponentially over the last 100 years and it is still evolving. Engineers and experts are constantly finding new and better ways to do things such as to simulate, monitor, measure, and manage the drilling fluid life cycle.