In 1986 Dando Drilling International, a long established British manufacturer of drilling rigs for a diversity of applications, was approached by Kaltim Prima Coal (KPC), one of Indonesia’s large mining companies, for the provision of reliable and durable machinery for open pit coal exploration in East Kalimantan, particularly in Sangatta, some 120km north of Samarinda, the capital of East Kalimantan.
Successful Drilling Technique
Dando’s experienced and skilled commissioning engineers travelled into the rain forest of East Kalimantan to instruct and train a KPC crew on the use of what was then regarded as revolutionary machinery;-the D250, a hydraulic, top-drive, track mounted drilling rig which has since evolved into the current Mintec 12.8 model. Coal exploration initially commenced using open hole drilling with water flush followed by wireline coring. However the need for faster drilling rates prompted the adoption of air-flush drilling, this method proving both rapid and more cost-effective. The machine was able to take HQ cores to considerable depth.
Air flush for coal exploration was first developed in the coal fields of Northern England, and is now regularly used worldwide. It is ideal for consolidated formations including sandstones, mudstones and clays and excellent core recovery can be obtained.
The Dando Mintec rigs at KPC proved an unmitigated success, ripping through the first 300m at impressive rates using air-flush before switching to water flush to reach target depths. 26 years on and KPC now has a fleet of seven Dando drilling rigs operating. The latest incarnation, the Mintec 12.8 has evolved specifically for drilling in Indonesian type coal measures and Dando believes they are the leading manufacturer in this respect. These days the latest Mintec 12.8 rigs typically drill through the water table at extraordinary speed using open hole air-flush, then the hole is logged using a wireline gamma logging system. Once the data is analysed the bores are revisited for H coring.
Development of Mintec 12.8
The current Dando Mintec 12.8, boasting a 12,800 kg pull back capacity, is hugely popular for coal exploration in Indonesia and 18 of these machines have been supplied to the area so far. The rig has been specifically developed for very fast open hole air flush drilling with PCD bits and coring (wireline and conventional) in Indonesian type coal measures. Managing Director Martin Fitch-Roy states: “With this method, our clients are typically completing 300-400 m boreholes in a 20 hour shift.” The modern coal exploration machine is mounted on caterpillar tracks with a 900 CFM/350PSI air compressor and a 540 horse power caterpillar engine. Single bar grousers help the tracks clear easily and ensure the rig never struggles for traction. The machine also has wider application being capable of wireline drilling as well as RC drilling (Reverse Circulation) and RAB drilling (Rotary Air Blast.) With a multipurpose 6 speed rotary head, the rig can also take care of mine site drainage holes if needed.
Dando has a strong and established market in South East Asia with a long history in Indonesia supplying equipment not just to KPC but other major players in the Indonesian mining sector. Martin Fitch-Roy is confident about the future: “Dando has grown and prospered by listening to the needs of our customers, constantly developing our drilling equipment and providing bespoke solutions for core drilling in Indonesia.”