AMC SRU™ delivers $20,700 savings to operation in Western Australia

AMC’s challenge was to reduce the customer’s operational costs and environmental impact on site in the Sandy Desert, East Pilbara Western Australia. The SRU™ proved to be a financial benefit, not a cost, demonstrating savings in mud consumption, water usage and KPIs and benefiting the environment through the elimination of sumps and reduced site footprint.

AMC SRU™ achieved:

• $20,700* savings per rig per month
• 50% reduction in mud volume
• 80% reduction in water usage
• sump no longer required
• 10% increase in kpi's

* Rental is not included as rates may vary depending on the terms of the contract.

Background

In Australia, AMC’s customer received pressure from the community and government regulations to reduce the impact of their activities on the environment as well as reducing the cost of exploration drilling.

AMC’s Solids Removal Unit™ (SRU™) was trialled to reduce the cost of exploration drilling and environmental impact on one of the rigs at gold-copper mines in the Great Sandy Desert in the East Pilbara region of Western Australia. Drilling is challenging as the type of stratification changes quickly over a few metres from soft clayish ground to hard glassy sandstone quartzite that has solidified.

50% reduction in Mud costs

Mud utilisation reduced by 50% (assuming 90 - 100% water circulation) when circulated through the SRU™ closed-loop system (3000L), as opposed to utilising mud sumps (approx. 21,600L). Data obtained showed potential savings of 30%, even if water circulation reduced to 70 - 80%, due to circulation losses caused by poor geology. Potential savings were $16,200 per month or approximately $540 per day.

Eliminated Need for Mud Sumps

The SRU™ replaced the need for 3 x ~7200L mud sumps. An external mixing tank (approx. 2000L) was used for rig suction, mud preparation and control of overflow from the SRU™. Savings associated with digging and re-mediating the sumps was estimated to be approximately $1000 (depending on ground and geology conditions).

Up to 80% Less Water Used

The trial demonstrated water could be reduced by 50 - 80% by replacing the sumps (21,600L) with the SRU™ (3000L) and an external mixing tank (2000L). Water was pumped directly from the bores to the sumps; therefore cartage costs were not incurred. From time to time water supply, and subsequently drilling activity, was interrupted due to maintenance at the mill. The SRU™’s unique closed-loop system retained optimal fluid levels and eliminated problems typically experienced with open sumps. As a result, the operator reduced downtime and associated costs.

Up to 98% Reduction in Cuttings Volume

The SRU™ reduced the overall volume of mud cuttings by up to 98%. The condition of the cuttings from the SRU™ chute was also dry and stiff (approximately 70% dry, with 30% water), which enabled simple removal from site and easy access to municipal disposal sites.

Smaller Site Footprint, Lower Environmental Risks

The SRU™ significantly reduced the site footprint by eliminating the need to dig sumps. It also reduced the risk of poisoning or drowning to wildlife. Less water was consumed and the risk of ground water or local waterways being contaminated from sump seepage was also removed.

HSE Benefits Reduce the Risk of Injury

Every resource company would like to send operators home in good health and provide an injury free environment to work in. Less rod trips limits the crew’s exposure to injury, heat exhaustion together with physical exertion in the dry hot conditions experienced in the Pilbara region.

Consistent Mud Properties Achieved

AMC recorded mud and rheological properties throughout the trial. The mud properties were kept relatively consistent and clean, indicating the unit did not remove polymer, only undesirable cuttings.

Plastic Viscosity

Plastic viscosity is a good indicator of solids control. If the volume of solids increases, due to an increase in cuttings concentration, or a reduction in particle size due to grinding at the drill bit face, the plastic viscosity will increase indicating that the mud is not cleaned properly. Solids build up in a mud system causes stuck pipe, dirty or a clogged back-end assembly, an increase in Marsh funnel viscosity and wear and tear on equipment. During the trial, the plastic viscosity of the mud remained consistent over a four week period, indicating the mud was cleaned adequately.

Yield Point

Changes in the yield point indicate chemical contamination may occur due to an increase in smaller particles and causes instability in the rheological properties. The yield point remained stable throughout the trial, indicating the mud was running at optimal condition.

Anaerobic Biodegradation

The hot and dry environmental conditions in the Pilbara region can cause the anaerobic biodegradation of mud at the bottom of the sumps – the size of the sumps and slow flow rate exacerbates this problem. When contaminated water is transferred from the sump to the mixing tank, the bacteria can also cause the mud to breakdown before it is used. The SRUs closed-loop technology overcomes this problem as mud is kept at optimum condition and is continuously flowing.

Specific Gravity

The specific gravity reduced between the collar and centrate, indicating the SRU™ centrifuge was successfully removing heavy cuttings.

Summary of Rheological Properties of Mud

	RHEOLOGICAL PROPERTIES OF MUD FROM COLLAR	RHEOLOGICAL PROPERTIES OF CENTRATE FROM SRU™
Viscosity	35-37 secs	35-37 secs
Rheology 600 rpm (cPs)	13-17	12-19
Rheology 300 rpm (cPs)	8-10	8-12
Plastic viscosity (cPs)	5-7	3-7
Yield point (lb/100ft2)	2-5	1-6
Specific Gravity (SG)	1.02 – 1.04	1.00 – 1.02
Filtrate (ml, 30 min)	12-16 ml	12-16ml
Sand content	0.25 – 0.75%	Nil

Particle Size of Cuttings Reduced to Less Than 10 Micron

Clean mud in good rheological condition is essential for the successful and economic completion of a drill hole. The typical particle size of cuttings within drilling fluid pouring from the collar during diamond drilling is approximately 0 -1000 microns. When utilising the SRU™, the particle size reduced to less than 10 micron (this includes the particle size of the drill fluid itself).

Cleaner mud containing smaller and fewer particles improves downhole utilisation of drilling equipment and reduces its wear and tear. As a result, replacement, maintenance and downtime costs are reduced.

Project Outcome

The SRU™ trial concluded that the SRU™ proved to be a financial benefit, not a cost, when calculating the potential savings for the Pilbara site. A calculated total of AUD$20,700* savings were created by utilising the SRU™ per rig per month.

Feedback from drillers was positive, the SRU™ was compact and easy to use and operated well with minimal attention. The drillers noticed reduced mud usage, “There were shifts where little to no mud was added”.

Using the SRU™ had a profound effect on the productivity of the drillers, “Mud preparation was replaced by mud checking – our guys had more time to monitor properties and fluid levels”. Typical daily tasks included removing cuttings from the chute, check the water levels and daily maintenance. During this trial there were no stuck pipes, less friction on rods and hole, drill deeper without casing off, mud was kept clean by the unit and the drill bit lasted longer (saving reaming time of 1-1.5 hour and one rod trip of 4-6 hours when at 800m. The savings on man hours and reduced rod pull and reaming created a safer work environment. A 10% improvement in KPIs per shift per day meant a potential saving of $18,000 per month

Cost savings were principally generated from improved KPIs per metre, reduced mud usage, elimination of need for sumps, reduced cost of site preparation of sumps, reduced environmental impact and site re-mediation costs, reduced volume of cuttings (up to 98%), savings for the drill operator (equipment wear and-tear and rig downtime due to maintenance), cleaner mud system, increased rate of penetration and reduced amount of water used or lost down hole.

For more details on this successful project, contact [email protected]