Let’s make our point upfront: 1) bentonite-based drilling fluid is NOT bad for horizontal remediation well (HRW) projects; 2) it does not damage the formation; 3) it is a naturally occurring clay material that is mined, and 4) it does flush easily/ adequately during well development.
Most remediation professionals have designed and/or installed vertical wells at one time or another during their careers. After advancing the boring, setting the screen/riser and sand pack, the driller usually pours dry bentonite chips or pellets into the annular space between the well and formation. The driller then adds water to hydrate the bentonite, creating a very effective seal as the bentonite swells (or “yields”).
Why are we discussing a topic that is common knowledge/ practice to most remediation professionals? Because some people who claim to be experts at installing horizontal remediation wells assert that bentonite-based drilling fluids damage the formation and cannot be adequately flushed from the annular space during development. These are false assertions that distort what actually happens when bentonite-based drilling fluid is used. These false assertions feed off of most remediation professional’s real-world experience when dry bentonite is intentionally hydrated in situ to create a seal in a monitoring well. In other words, an attempt is being made to make you think that because straight bentonite hydrated in situ makes a great seal, it does the same thing when used in a drilling fluid when installing an HRW.
The argument turns on the fact that: 1) bentonite-based drilling fluid is hydrated ex-situ and yields prior to commencing drilling; and 2) bentonite is a component of the mud system, not the sole component. A “seal” is never formed by bentonite in an HRW and in addition, Directional Technologies, Inc. uses a proprietary process to develop HRWS based on years of field experience in the oil field, the utility industry, and the environmental industry. This development process results in fully functional wells.
The same HRW professionals that criticize bentonite-based drilling mud also advocate the use of “bio-polymer” drilling muds. These are manmade products based on gaur gums and vegetable products that biodegrade after use to various types of sugars that purportedly “jump-start” the bioremediation process by supplying nutrients to naturally occurring bacteria. The problem with this is that the sugars tend to enhance undesirable bacteria that can create slime that damages the formation.
Directional Technologies, Inc. develops and formulates specific drilling fluid programs for each HRW we install. We do not use a one-dimensional, “one-size-fits-all” drilling program. There is both a science and an art to creating the optimal fluid program for each well installation. It is imperative that the selected drilling fluid(s) build the bore path to: 1) prevent formation damage; 2) enable safe cost-efficient drilling/well installation; and 3) prevent bio-fouling.
99% of our 1,000+ Horizontal Remediation Wells have been directionally drilled with a bentonite-based drilling fluid! That includes 100’s of site closures and No Further Actions. Still, after 22 years, the debate below goes on. The previously distributed article below gives you some additional insight. To further the discussion and promote full disclosure, DTI has consistently found that the cost of disposing of bio-polymers is higher than directionally drilling with bentonite-based drilling fluids. However, that additional cost is typically not compared and the unsuspecting consultant ends up with a disposal cost sometimes 50% higher than bentonite-based drilling fluids. Since this cost is not included in the scope of the work, it can be a very large, unwanted, hidden cost.