Schlumberger

Case Study: Efficient One-Run Perforating on TuffTRAC Tractor from Space-Constrained North Sea Platform

Tractor first sets plugs for depressuring well to enable rigging up long gun string

Challenge: Perforate a net 30-m interval at 86° deviation from a North Sea platform with limited deck space and rig-up height.

Solution: Use the TuffTRAC cased hole services tractor to

  • install bridge plugs to seal off existing perforations and allow pressure to be bled down
  • convey 50-m string consisting of the tractor and guns to perforating depth
  • push guns released after firing to below the perforated interval before retrieval of the shortened string.

Result: Successfully perforated the interval in one run underbalanced without requiring a rig for coiled tubing deployment.

Complicated conditions: platform and downhole

A North Sea operator wanted to perforate a net 30-m interval at 86° deviation. The tortuous well trajectory would have caused high cable tension when pulling out of the hole, and the restricted deck space on the platform and limited crane capabilities for rig-up height and lift capacity were controlling factors for wireline-deployed perforating gun length. However, a rig was not available for using coiled tubing to convey the perforating guns, and the operator wanted to perforate the entire interval in one run.

TuffTRAC tractoring versatility

Although the TuffTRAC cased hole services tractor is the shortest tractor in the industry, it also features active traction control and reverse tractoring capability for superior maneuverability in complex wells. The robust modular, low-power design easily withstands the impact of perforating gun firing and gun release, conveys heavy loads, and negotiates difficult completions.

In addition to wireline logging and perforating services conveyance, the TuffTRAC tractor is ideal for performing remedial operations in producer and injector wells, including plug setting.

One-run tractor-conveyed perforating

To provide space for making up a sufficiently long gun string to perforate in one run, first the currently perforated zone was isolated by setting two bridge plugs with the TuffTRAC tractor to effectively seal off all open perforations. The well pressure was bled down, and then the subsurface safety valve was closed to form an additional barrier. With the pressure relieved, a gun string incorporating a WXAR automatic gun release could be made up that otherwise would not have fit in the height available above the Christmas tree. The total length of the guns and tractor was 50 m.

After the TuffTRAC tractor was used to convey the long gun string to shooting depth, the well was repressurized with nitrogen gas to achieve underbalance. Once the guns had been detonated and released with the WXAR release, the TuffTRAC tractor pushed them below the newly perforated interval and then pulled the significantly shorter toolstring out of the hole to be conventionally rigged down under pressure.


Download: Efficient One-Run Perforating on TuffTRAC Tractor from Space-Constrained North Sea Platform (0.19 MB PDF)

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