Evaluation Standards

PrintThe evaluation requirements for a particular well depend upon the type of well being drilled eg., development, appraisal or exploration.  The detailed requirements for each well shall be indicated in the Well Proposal.

1. Evaluation Standards

Evaluation Categories

Typically, the formation evaluation carried out by the Drilling Department falls into two categories:

Formation evaluation undertaken as a service for customer departments to obtain reservoir parameters and/or production engineering data

Formation evaluation carried out to obtain information for drilling engineering purposes

Evaluation carried out for drilling engineering purposes includes pore pressure analysis, formation integrity tests and some formation evaluations while drilling (LWD). The requirements, policies and procedures for this evaluation are fully controlled by the Drilling Department.


Evaluation carried out for customer departments includes:

  • Wireline Logging
  • LWD
  • Coring
  • Mud Logging
  • Production Testing.

The requirements for this evaluation including quality control are determined by the customer departments. Policies and procedures for executing the evaluation including responsibility for safety, quality and logistics are under the control of the Drilling Department. Some of the data obtained for customer departments, for example reservoir pressures and sonic log data may also be used by the Drilling Department for engineering future wells.

Evaluation Mainly for Reservoir/Production Data

Evaluation Mainly for Drilling Engineering Purposes

Wireline logs
Mud logging
(Pore pressure prediction)
Production logging
Wireline survey (Pressure Build up Survey)



2. Wireline Logging Standards

Log Requirements

For wireline logging operations, all logs obtained shall comply with standards specified in the Logging Contract. Each tool has a checklist in the Contractor’s Quality Control Manual. Each tool is checked for calibration responses and repeatability

Radioactive Sources

The use of radioactive sources in logging operations shall be in accordance with Company Radiation Manual for Well Logging Operations.


Explosives charges must be transported and stored in specially designed containers, with primary and secondary explosives stored separately. The Logging Company Engineer has sole permission to remove explosives from the storage containers and to arm or disarm any tool using explosives. For onshore operations the explosives are transported on public roads with a police escort.

Pressure Control Equipment

Pressure control equipment shall only be tested with glycol or water/glycol mixture. Testing shall never be carried out with a live perforating gun installed.

For operations requiring pressure control equipment with the multi-conductor cable, both a ram BOP and hydraulic stuffing box are required.

When cased hole perforating operations are being performed in a well with pressure above normal hydrostatic, it is not necessary to run a shooting nipple so long as there is a readily available and tested device (eg., wire cutter or bolt cropper) for cutting the cable cleanly and efficiently. Otherwise a shooting nipple shall be used.

3. Geological Evaluation Standards


All core barrels shall be routinely checked at surface for the presence of H2S prior to core recovery. All non-essential personnel shall be removed from the drill floor at this time. The core is recovered with personnel in H2S gas mask and cut into sizes of 3ft. The cut cores are marked on top and bottom for easy identification in the core lab.

Mud Logging

A fully pressurised and computerised Mud Logging Unit shall be available at the well site for all drilling operations. The services provided shall comprise mud logging, formation pressure detection and formation tops.

Formation Strength Tests and Formation Breakdown Tests

Formation strength tests (or leak-off or shoe limit tests) shall be scheduled below all casing shoes (or outside milled casing windows for sidetracks) in exploration and first round appraisal wells, and below casing shoes (or outside milled casing windows for sidetracks) above hydrostatically pressured hydrocarbon bearing and/or over pressured sections in all other wells.

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