India’s first Sandvik DT1130 jumbo rig delivered to major cavern project

Published 2011-06-17 21:34:23

Fourteen Sandvik underground jumbo drill rigs are being used on India’s three strategic crude oil storage caverns under construction, in drill and blast duties to excavate more than 9 million m³ of rock from the 24.4 km of tunnels and caverns to store 5.33 million metric tonnes of crude oil – with the Deputy Project Manager for the S K E&C - KCT JV on the Padur project contract 1B, Prasanna K.M, stating that the Sandvik rigs represent “the lifeline of the project.”

The strategic crude oil reserves will be stored in underground rock caverns being considered the safest method of storing hydrocarbons in terms of longevity and security.

All three proposed sites are located close to the east and west coasts so that they are readily accessible for the refineries and ports.

Construction of all three sites is being managed by the Indian Strategic Petroleum Reserves Ltd (ISPRL) with prime consultant EIL (Engineers India Ltd).

India’s first Sandvik DT1130 underground jumbo 3-boom drilling rig has been delivered to the South Korean Engineering & Construction Co – Karam Chand Thappar Joint Venture (S. K. E & C – KCT JV) for the third of the country’s three crude oil storage caverns – together with two Sandvik DT820 2-boom rigs and a second DT1130 to be delivered in April 2011 – for its Phase 1B contract. 

The Padur project has been awarded as two identical packages with Hindustan Construction Co (HCC) winning 1A - the second contract - and relying on three Sandvik DT820’s for the underground excavations. The combined capacity of both contracts will total 2.5MMT of crude oil.

Located close to the village of Padur – meaning hard rock in the local Kannada language – in Udipi district, Karnataka State, 70 km north east of Mangalore, the location was chosen for its very hard Class 1 Black Granite – Gneiss Schist rock; with a hardness factor of greater than 100MPa and a Q value of almost 1.

Contract 1B

The S K E&C – KCT JV initiated site mobilisation in May 2010 and begun tunnelling operations in October and, by March 2011, had completed 450 m of access adits and 150 m in the water curtain gallery. 

Providing access to the underground workings, the adit features a total of 120 x 45 mm diameter holes drilled across the 11 m x 8 m high cross section using the three Sandvik rigs.

The access adit is being prepared at a gradient of 15º throughout excavations except along the horizontal junctions. Routed 150 m before the first junction to the water curtain gallery, the access portal continues for a further 268 m before opening as a junction to provide access to both ends of the first cavern.

In total, the access adits will be 1900 m long and enter the cavern headings 100m from both ends. Before excavation of the cavern heading can begin however, work must have been completed on the water curtain directly above.

Water curtain gallery 

The water curtain gallery is being used for the first time in India in the construction of all three storage cavern projects and represents an essential aspect in the construction programme.

Featuring a 6.5 m wide and 6 m high cross section, the 800 m long gallery will feature 70 x 70 m long x 102 mm diameter bore holes drilled on both sides at an inclination of 10º; to totally encompass the top of all four caverns 40 m below.

The boreholes will then be sealed and pumped with high pressure water in a continuous recirculatory system at 6 bar to seal any fissures in the rock around the caverns.

The water will prevent seepage of crude oil fumes through the fissures, eliminating the possible risk of explosions. 

Caverns

Once the water curtain has been proven the contractor anticipates preparation of the first header of the four caverns by the end of July.

All four caverns are each 700 m long and 20 m wide with caverns 1 and 4 having a height of 30 m and 2 and 3 a reduced height of 22 m. The crowns for all four are set at – 40 m and the base of 1 and 4 being – 70 m.

The four caverns are each spaced 20m apart with 1 and 2 connected together as are 3 and 4 to form two ‘U’ shapes. 

During drill and blast operations with the Sandvik rigs, the header access adit continues 20 m through to provide access to the next cavern.

On completion of the 8 m high header, the joint venture will prepare a ramp down to the bench below then cut back to drill and blast the 8 m high bench 1.

A similar process is repeated for each of the remaining two benches to complete the full cavern heights of 30 m and 22 m respectively.

By completion of the caverns, 4 m x 4 m inlet shafts will be excavated into the sides of caverns 2 and 3 together with 12 m x 6 m outlet shafts directly into the crowns of 1 and 4.

Throughout excavation only a strictly regulated 400 mm tolerance is permitted to ensure a smooth wall finish; so as to reduce the possibility of voids filling with crude and the accumulation of vapours. 

During tunnelling operations, shotcreting is applied to offer additional support and a smoother surface using a steel fibre mix shotcrete; generally to a thickness of 100 – 150 mm.   

Sandvik Tools   

All three jumbo rigs are fitted with Sandvik R38/R32 drifter rods and R38 shank with 45 mm diameter button bits to drill 3 m – 5 m deep holes, depending on the rock and specification.

“We have been extremely impressed with the performance of the Sandvik tooling,” says Planning & Scheduling Manager, Yong Wan Song, adding, “With on site regrinding we have been able to achieve up to 200 drill metres with each button bit: regrinding after the first 80m.”

The joint venture has also been able to achieve 3000 drill metres for the drifter rods and as much as 5000 drill metres with the shank. 

Currently the SK E&C – KCT JV is anticipating a 12 hours cycle during drill and blasting in the caverns.  “I am confident that we will maintain this cycle rate particularly when the second DT1130 has been delivered.”

Says Deputy Project Manager, Prasanna K.M., “I am a great believer in the speed of the 3-boomer and it’s 11 m reach, so much so that l specified no basket so as speed drilling further. I am a great believer in the operator checking holes 1 and 2 then programming hole 3 whilst the other booms are drilling. It’s a fast process.”

The Sandvik rigs are also used with all booms for rock bolting duties. 

“The Sandvik jumbo’s really are the lifeline of the project.”

Blasting techniques

Cartridge type explosives are being used generally with 3 – 6 kg/hole.

Access faces - 140 holes using approximately 600 kg.

Gallery faces - Approximately 90 close holes – 300 kg.

Cavern faces (header) – 200 holes – 650 kg

Contract 1A

Main contractor for phase 1A Hindustan Construction Co. (HCC) also initially used conventional explosives from October 2010 but, following the success with liquid explosives on its Vizag cavern contract, applied for the relevant licence to introduce the liquid type to Padur. 

As a result of the license being approved HCC started to use the liquid format with 540 kg for the access adit, 270 kg in the curtain water gallery and 600kg in the cavern header – to offer a faster cycle time of 10 hours compared with 12 hours on the adjacent 1B. However,  S K E&C – KCT JV Deputy Project Manager, Prasanna K.M,  considers that this lost cycle time in using conventional explosives, is compensated by using the Sandvik 3 boom rig to provide faster drilling rates over the tunnel face.

Both contracts will be ‘plugging’ all the access junctions and handing over as a complete installation by May 2013.

Future development 

Plans are underway to expand operations under Phase 2 offering doubled capacity of 5 Mmt as normal storage; discharging directly from the tankers 15 km at sea and a further 12 km by land side pipeline.

Sandvik DT1130

The Sandvik DT1130 is a controlled three boom electro-hydraulic drilling jumbo for tunnelling and cavern excavation of 20 – 183 m2 (215 – 1905 ft2) cross sections; offering an 11 m reach.

Equipment with 3 x HLX5 rock drills and TB150 booms, it offers a large optimum shaped coverage.

Sandvik DT820

The Sandvik DT 820 is a two-boom electro hydraulic jumbo for fast and accurate drilling in tunnelling and cavern excavation of 20 to 110 m2 cross sections.

It is equipped with an HLX5 rock drill and a TB 90 universal boom, which gives a large optimum shaped coverage and full automatic parallelism. The booms can also be used for cross-cutting and bolt hole drilling. An optional basket boom for bolting and utility works is available. The four-wheel-drive centre articulated carrier ensures rapid and safe tramming with good balance.