How do you choose between water-based and oil-based drilling fluids?

1 Formation characteristics

The first factor to consider is the nature of the formation you are drilling. Some formations are sensitive to water, meaning that they can swell, disperse, or collapse when exposed to water-based drilling fluids. These formations include clays, shales, and salt. In such cases, oil-based drilling fluids are preferred, as they do not interact with the formation and prevent hydration and dispersion. Oil-based drilling fluids can also reduce the formation damage caused by fluid invasion and improve the well productivity.

2 Drilling performance

The second factor to consider is the drilling performance you want to achieve. Oil-based drilling fluids have some advantages over water-based drilling fluids in terms of drilling efficiency and quality. For example, oil-based drilling fluids can reduce the friction and torque in the drill string, enhance the rate of penetration, and lower the risk of stuck pipe. Oil-based drilling fluids can also provide better hole cleaning, borehole stability, and shale inhibition. Moreover, oil-based drilling fluids can withstand higher temperatures and pressures than water-based drilling fluids, making them suitable for deep and high-pressure wells.

3 Environmental impact

The third factor to consider is the environmental impact of the drilling fluid. Water-based drilling fluids are generally more environmentally friendly than oil-based drilling fluids, as they are biodegradable and have lower toxicity and flammability. Water-based drilling fluids can also be disposed of more easily and cheaply than oil-based drilling fluids, as they do not require special treatment or handling. However, water-based drilling fluids can still have some environmental issues, such as salinity, metals, and additives. Therefore, it is important to comply with the regulations and standards for drilling fluid disposal and management.

4 Economic cost

The fourth factor to consider is the economic cost of the drilling fluid. Oil-based drilling fluids are usually more expensive than water-based drilling fluids, as they have higher base fluid and additive costs. Oil-based drilling fluids also incur higher transportation, storage, and disposal costs, as they require special equipment and facilities. However, oil-based drilling fluids can also save costs in some aspects, such as reducing the drill bit wear, increasing the drilling speed, and improving the well productivity. Therefore, the economic cost of the drilling fluid should be balanced with the benefits and risks of using it.

5 Operational challenges

The fifth factor to consider is the operational challenges of using the drilling fluid. Both water-based and oil-based drilling fluids have some drawbacks and limitations that require careful monitoring and control. For example, water-based drilling fluids can lose water due to evaporation or filtration, resulting in changes in density, viscosity, and rheology. Water-based drilling fluids can also be affected by contamination from salts, gases, or solids. On the other hand, oil-based drilling fluids can have problems with emulsion stability, oil-water separation, and oil retention. Oil-based drilling fluids can also pose safety and health hazards, such as fire, explosion, and exposure.

6 Customer preference

The sixth factor to consider is the customer preference for the drilling fluid. The customer is the one who ultimately decides which type of drilling fluid to use, based on their objectives, expectations, and requirements. The customer may have a preference for water-based or oil-based drilling fluids, depending on their experience, knowledge, and perception. The customer may also have specific criteria for the drilling fluid performance, such as drilling time, wellbore quality, and production potential. Therefore, it is important to communicate and collaborate with the customer to understand their needs and preferences and to provide them with the best drilling fluid solution.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?