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GBS Large Diameter Geotechnical Wireline Core Barrel

This highly versatile core barrel system is used widely in geotechnical works to obtain large diameter cores in a wide range of geological formations.

GBS is particularly effective when high quality cores are required in clay, sand or loose, weak formations. The standard core of 102mm is completely retained in a clear PVC Coreliner and is easily extracted in one piece after each core run.

The inner tube assembly latches inside the outer core barrel and is lifted to the surface by a overshot device connected to a wireline cable. The wireline retrieval method greatly improves production rates compared to conventional coring method but also leaves the borehole fully cased at all times ensuring borehole stability in sensitive geology.

There are several different methods of using this core barrel:

Method 1: For coring medium to hard formations. The bit setting is 146mm OD x 102mm ID. TC or diamond bits can be used depending on geology.

Method 2: For coring in soft formations.  TC bits are mainly used which consist of two parts – pilot and reamer. The reamer OD is 150mm and pilot ID is 102mm.

Method 3: For coring in very soft or loose formations. The bits are the same as method 2 but a special extended core lifter case runs 25mm in front of the bit.

Method 4: For coring in very soft or loose formations. The core lifter case is extended to run 60mm in front of the bit. The inner tube is spring loaded so that the core lifter case retracts behind the bit when harder formations are encountered. The bit setting is 146mm OD  x 109mm ID

Method 5: Shelby tube sampling of soft or very soft formations. This is an attachment that replaces the inner tube and has at the bottom end a shelby tube which samples ahead of the bit. The bit is same as method 1

Method 6: Full hole drilling assembly, this is an attachment that replaces the inner tube for non-coring purposes. The core bit is same as method 1 and the non-coring bit is 101.6mm diameter.  For pilot coring ahead of the GBS barrel, it is possible to attach a smaller diameter core barrel (T6-101 or smaller) in place of the non-coring bit.

Advantages:

  • Large diameter, high-quality core
  • Ability to obtain good recovery in a wide range of geological formations
  • Excellent hydraulics
  • Very versatile system

Technical Data

Specification Drilling Method
Method 1 Methods 2 / 3 Method 4 Method 5 Method 6
Hole Diameter (mm) 146.0 150.0 146.0 146.0 146.0
Core Bit set I.D. (mm) 102.0 102.0 109.0 102.0 102.0
Core Diameter (mm) 102.0 102.0 102.0 95.0 N/A
Kerf / Crown Thickness (mm) 22.0 24.0 18.5 22.0 22.0
Hole Area (cm2) 167.5 176.8 167.5 167.5 167.5
Core Area (cm2) 81.7 81.7 81.7 70.9 N/A
Recommended Drill Rod GBS Monobloc
Recommended Casing SW