After testing new slim hole drill strings that are able to perform destructive drilling and wireline coring with positive drilling achievement and positive geological data acquisition, the construction of a purpose built rig for slim hole drilling has been undertaken. It is believed that a purpose built rig will lead to substantial drilling cost breakthroughs and greatly reduce the environmental impact of the drilling operation.

Reducing the Drilling Cost
  • One method to reduce drilling costs is to perform the drilling operation more efficently. This includes but is not limited to operating with fewer people. To do this it is necessary to review the different tasks performed by personnel on the rig. To perform those tasks with fewer people we must install simple, safe and reliable equipment.

Environmental protection
  • Foot Print : The rig is designed for a site having an area less than 850 square meters (about the size of a tennis court).

  • Waste Control : Drilling will be done without a mud pit (reserve pit). The initial physical and chemical treatment of the mud will be done by the rig crew. All waste materials will be recovered and stored in containers. This greatly minimizes the impact on the environment. Note that the slim hole produces considerably less waste than conventional drilling.

  • Noise Control: Special care concerning the packaging of the prime movers and drawworks was used to achieve an overall total reduction of noise.

  • Optimization of Standard Loads : Hie individual loads are designed with a maximum in weight and dimension of about 1/3 of the normal rig size load. This reduces the impact of the environment, especially in remote, sensitive areas.

Slim Hole Prilling Practices

Slim hole drilling requires a refined control and measurement of all drilling parameters. To achieve this, we need:

  • All sensors are permanently installed in the right position on the rig and are linked to an industrial network which delivers the data to the key participants to the drilling process. The type of sensors used are completely detailed in the paper.

  • PLCs and adequate software to monitor and control the various DC motors directly linked to the essential mechanical functions; speed, torque, rotation, weight on bit and the mud pumps output.

Slim hole drilling requires a new rrange of flow parameters versus conventional practices. An original solution has been developed and is presented in this paper.

Based on the above criteria the paper will detail the solutions that provide the foundations adopted to build the slim hole purpose built rig. The rig has begun operations in France in April 1994. The initial results will be available.

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