Sigra manufactures 101 mm and 127 mm bore annular blowout preventers, chokes and wireline strippers. These systems are primarily used with HQ and PQ wireline coring in gassy formations.
In 1994, Sigra was given a contract to design and build a borehole pressurisation system for underground coal mine drilling. One of its notable features was the choke which, being an elastomeric device, could pass large particles transported in the drilling mud while maintaining back pressure and without blocking.
In 2001, Sigra was approached to build a blowout preventer (BOP) system for Lihir gold mine in Papua New Guinea. The purpose of this was to enable highwall drainage drilling in geothermal conditions. The boreholes were drilled using SIMCAS with a hammer and casing. The BOP system permitted the safe withdrawal of all drilling equipment from the hole.
In 2004, Sigra started to supply the first of some 70 well control systems used in exploration core drilling in gassy conditions. These have been used in coal mining and coal seam gas exploration.
In 2013, a variant of Sigra’s well control system was used for site investigation drilling for the 30 km Temburong bridge in Brunei.
In 2015, Sigra supplied underground well control units to BHP-Billiton Illawarra Coal operations.
In 2016, Sigra was commissioned to build a pressure control system to enable managed pressure drilling from below the groundwater table from inside the Liang Tang tunnel in Hong Kong for VSL Intrafor / Dragages.
Sigra Wire Line Coring Well Control Suite
Sigra manufactures a suite of well control tools specifically for use in HQ size wire line coring. They are ideally suited for use in coal exploration where gas may be expected. The system may also be used for open hole drilling. Figure 1 shows one of the systems while Figure 2 shows the arrangement for use.
The suite of tools is comprised of:
- Annular blow out preventer
- Pressure relief choke
- Activation unit
- Wire line stripper
Annular Blowout Preventer
Sigra blow out preventers are small, lightweight annular devices that operate in the lower pressure ranges where most coal reserves are found. Their inflation is via water or water –glycol mixes such as is used in vehicle coolant. They are actuated by hand or motorized pumps with accumulator storage.
Sigra makes a range of BOPs in two sizes, 4” and 5”, as shown in Table 1. Their working pressure ratings vary between 7 MPa (1000psi) and 13MPa (1900psi). All units come fitted with choke and kill ports. They are normally fitted with minimal height overflow mud collectors.
Table 1. Standard Sigra blow out preventers.
Pressure Relief Chokes
Sigra chokes are not just restrictive valves – they are pressure relief valves that are made from an energized reinforced elastomer. This enables to pass cuttings while maintaining a constant back pressure. They may be used for well control in underbalanced drilling. Sigra chokes are manufactured in a number of sizes to suit varying flow rates. Two of the most common are:20mm – designed maximum flow rate = 100 litres/minute
25mm – designed maximum flow rate = 250 litres/minute
These chokes are capable of maintaining a regulated pressure relief setting between 0 and 10 MPa (1450 psi).
Sigra also make low pressure chokes civil engineering applications.
Wire Line Stripper
Sigra manufactures wire line strippers which are designed to prevent swabbing of a borehole while pulling an inner tube during wireline coring operations. They can also be used to seal around a wire line in the event of a blowout. They contain a pressure gauge port fitted with a quick connect and a bleed or kill port. They are lightweight devices designed to 89mm (3 ½”) outside diameter and fitted with HRQ or HQ threads.
The wireline strippers are energised by a hand hydraulic pump. Their seals are readily replaced.
They are capable of holding back up to 10MPa pressure (1450psi).
Sigra Wire Line Stripper Size
- 300 mm high × 89 mm diameter plus pump and hoses
- Weight = 8 kg
The Sigra manual activation unit is for use with both the 101 mm blow-out preventer and the 20 mm choke. It is simple to operate and provides excellent control. It is portable and compact and can be located up to 15 metres from the well. It is air operated with a manual pump for backup. Activation is by hydraulics.
Sigra Activation Unit Size
- 900mm long × 800mm high × 500mm deep
- Weight = 60kgs