Maximising drilling fluid performance in HDD

Geodrilling International speaks to Daniel Galpin, Drilling Optimisation Specialist at AMC about the maximising drilling fluid performance in HDD.
What are the key functions of drillings fluids in HDD applications? What would the ideal mud achieve?

The main function for a drilling fluid in HDD applications is hole cleaning. It is crucial to avoid cuttings beds forming, a build-up of drilled cuttings on the low side of the hole. Equally as important is promoting hole stability. We can achieve stability by keeping the hole full of drilling fluid, but also by maintaining formation integrity with adequate filtration control, encapsulation and inhibition of certain formations.

What are the trickiest parts of choosing the right drilling fluid for HDD jobs? What can go wrong if you make the wrong choice?
Matching the drilling fluid to the geology is of critical importance. Ideally investigation bores should be drilled along the proposed drill path to ascertain exactly what type of ground conditions are likely to be encountered.

Using the wrong type of drilling fluid for the formation can result in difficulties on the drill out, including pressurisation of the drill hole which can result in frac outs. Other issues can include high pull pressures, hole collapse and ultimately stuck product pipe.

AMC has a team of fluid engineers that provide local on-site support to improve productivity, resolve challenges and train drill crews. We have extensive experience in a variety of drilling operations and access to the largest drilling fluid laboratory in the in the southern hemisphere, allowing us to complete accurate mud programs and offer full hydraulic analysis of the planned bore hole. With our support, our clients are able to estimate mud volumes, select suitable products as well as flag any areas of concern regarding down hole problems and drilling fluid solutions.

How do the drilling equipment and technique affect drilling fluid efficiency?

The right selection of down hole tooling – drill bits, mud motors, reamers as well as efficient solids control equipment is critical to maximise efficiency of drilling fluids performance.

AMC hires specialised solids control equipment for HDD, including our AMC 1500 R™ double deck shaker system, capable of reclaiming up to 1,500L per minute. Also available is the AMC 2000 M™ mixing system capable of efficiently mixing up to 21m3 of fluid, complete with on board transfer pumps. AMC also offers a range of centrifuges which remove solids in the drilling fluid down to 5 micron, allowing even greater control of the mud system, minimising dumping and saving costs.

What are the main differences between HDD and vertical drilling fluids? How do the downhole conditions differ?
Generally HDD drilling fluids have enhanced low end rheology profiles. This allows for maximum hole cleaning by the drilling fluid. Rather than cleaning the hole through the action of mud pumps alone. AMC supplies a full range of drilling fluids to complement any type and complexity of HDD hole. Our specialty products include our proprietary mixed metal oxide (MMO) Bentonite extender AMC MAXI VIS™ together with our enhanced filtration control polymer AMC NEUTRA DEX™. As well as a range of products including high yield Bentonite (AMC GEL XTRA™), filtration control polymers (AMC EZEE PAC R™/L), encapsulating polymers (AMC COREWELL™) as well as inhibitive mud systems for highly reactive clays and shales (AMC SHALEHIB ULTRA™).

How is the drilling fluid disposed of?

Often the drilling fluid is processed through a reclaiming system, consisting of a series of shaker decks with screens and hydro cyclones. This physically removes drilled cuttings from the drilling fluid and allows spoil to be disposed of via conventional means. The recycled clean water is subsequently reused during the drilling operation. AMC can assist with optimising the use of drilling fluid to reduce overall consumption and make disposal easy – especially in areas of environmental restriction.

What are the latest innovations when it comes to HDD drilling fluids and related products? How have processes changed in recent years within the sector?

Some of the latest advancements in HDD related drilling fluids are flowing down from the oil field based technologies. Including the introduction of non-invasive fluids and amine based clay inhibitors, such as AMC SHALEHIB ULTRA™. AMC SHALEHIB ULTRA™ is effective in formations containing shale and reactive clay, and reduces the potential for bit balling, torque and drag. This product has minimal chloride content, making it far more environmentally acceptable than potassium chloride, which is typically used for inhibition. Our specialist HDD drilling fluids and equipment are designed for complex bores to be completed more efficiently, and most importantly, within budget. Could you describe the challenges and solutions of a recent HDD project you worked on?

Recently, AMC designed a drilling fluid system which was both effective in very sandy, loose overburden material, needing elevated hole cleaning rheologies while also being able to effectively inhibit and control reactive clays and shales. It was crucial that this fluid system was able to be reclaimed in a timely manner through the use of appropriate reclamation technology. This was done by using a polymer system consisting of AMC PAC R™ for filtration control, AMC XAN BORE™ to provide hole cleaning rheologies in combination with AMC SHALEHIB ULTRA™ to control reactive surface clays. AMC DET XTRA™ was also used to treat the stickiness of clays. Due to the product pipe being substantial, AMC TORQUE FREE XTRA™ was also utilised during the pull to ensure lubrication was maximised, minimising pressures while pulling the pipe. This drilling program enabled the project to be completed within budget and on time.

This article was featured in the September 2017 edition of GeoDrilling International Magazine