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Drilling Fluids for Difficult Drilling

Drilling Fluids for Difficult Drilling
Checking the drilling mud consistency. Photos courtesy of the International Continental Scientific Drilling Program.

Many people in the drilling industry are aware of the benefits of using bentonite drilling mud. Sometimes, though, they are not aware of the various types of bentonite products on the market. We often are asked what other products are available when bentonite drilling mud needs a boost in certain problem situations. There are several bentonite products on the market today, as well as several polymers and additives, that can be very beneficial.
Bentonite drilling products available today include:

  • 200 Barrel Drilling Mud -- high viscosity, low solids drilling fluid for all types of freshwater drilling.
  • 90 Barrel Drilling Mud -- API drilling mud.
  • Untreated Drilling Mud -- 60-90 barrel yield drilling mud, polymer-free and often used in environmentally sensitive drilling.
  • Specialty Drilling Mud -- commonly referred to as "one sack" or "one step," drilling mud designed mainly for horizontal directional drilling, but also used in unconsolidated vertical formations. It contains additives for pre-treating hard water, fluid loss control and maintaining borehole integrity.

Research continually is conducted to formulate new products for the drilling industry. This research is in response to specific problems brought to us by professionals in the field.
The bentonite products discussed above work in many different situations. However, occasionally, difficult soil conditions are encountered that require some extra help for the bentonite fluid. One of these situations is fluid loss control. Bentonite drilling fluid forms a filter cake around the outside of the borehole, but sometimes pressures are exerted on the borehole wall during the drilling process that require a thinner, tougher filter cake. There are certain polymers, called polyanionic cellulose polymers, that will minimize fluid loss to the formation and increases the stability to the borehole.
Drillers and contractors often are unaware of these polymers and have problems that could be prevented or minimized in these tougher drilling situations. In addition to the benefits of fluid loss control and borehole stability, these polymers can provide:

  • improved gel strength to promote cuttings suspension and removal
  • clay and shale inhibition and swelling prevention
  • increased fluid viscosity and fluid lubricity

These polymers are available in both dry and liquid form and easily are dispersed, providing a tremendous advantage for drillers.

Drilling Fluids for Difficult Drilling
Soft, unconsolidated rock can make for difficult drilling.

There also are some other types of products that are important to use in specific situations. Some of these include:

  • Polymers for reducing clay and shale swelling. These polymers usually are liquids but also can be purchased in dry form. They can be used alone as the drilling fluid or can be added to a bentonite mud system.
  • Polymers for sand control and other stabilization. These polymers mainly are available in granular form. They mix easily and promote soil cohesion.
  • Drilling Detergents. These products have become very popular in today's drilling industry. As wetting agents, they improve the efficiency of drilling fluids and help prevent stickiness and bit balling.
  • Thinners. Thinners are designed to thin back drilling fluids when they are too thick for effective pumping and drilling. They do not break down the drilling fluid but merely thin it. Larger amounts can be used to break down the bentonite wall cake during well development.

One of the most important factors for good, effective drilling is the make-up water used to mix the drilling fluid. It is very important to maintain a pH of 8-10 for bentonite drilling systems. Many times we find the pH of water for drilling to be low, so one can adjust the pH by adding a product called soda ash. It only takes a small amount and it is a very cheap investment.
All of the products mentioned above usually are available in your area. Contact your local distributor or bentonite manufacturer.
Courtesy National Driller

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