Mud and data logging comprise two distinct but complementary operations which may be combined, or alternatively mud logging may be carried out on its own.

1       General Requirements

Mud logging includes the following:

• Continuous logging of total gas and the chromatographic analysis of hydrocarbons.
• Detailed cuttings analysis including the description of lithology and hydrocarbon evaluation as specified.
• Taking of geological samples at the depths and in the manner required by the Company.
• Measurement and recording of bulk density.
• Correlation of cuttings lithology, gas analysis and hydrocarbon evaluation to reference material provided by the Company.
• Provision of daily reports as required.
• General assistance to Company personnel.
• Provision of personnel for core-catching operations and for detailed geological description of cores.
• Collection and description of sidewall samples.
• Collection and analysis of fluids from well tests as required.
• Monitoring and chart recording of basic drilling parameters.

Data logging includes the following:

• Monitoring and analysis of drilling operations and the recording of all data on tape or disc.
• Preparation of computer-processed printouts and plots of the recorded raw data and derived calculated data using standard software programmes.
• Preparation of the up-to-date pressure evaluation log incorporating the raw data plots of drill rate, corrected d-exponent, ditch gas values, shale density, etc.
• Preparation of up-to-date temperature data log using mud temperature parameters.
• Preparation of up-to-date pressure analysis log based on the above parameters giving the  estimated pore pressures, equivalent circulating density, overburden gradient, and estimated fracture gradient.
• Carry out formation pressure wire line log analyses as required to assist the company in evaluating the current downhole conditions relating to estimated formation pressure, formation gradient and casing shoe selection points.
• Provide a daily report on current drilling conditions as requested by Company Drilling Supervisor(s) or Well Site Drilling Engineer. The parameters reported include d-exponent, mud hydraulics, fracture gradient and estimated pore pressure and are derived from the basic software programmes or engineer determined values. Additional bit and cost calculations may be requested.
• Provide a weekly report detailing the drilling operation and any conditions of interest relating to abnormal formation pressure evaluation.

The full mud/data logging system is used for exploration wells, while for appraisal wells the data logging system may not be required if sufficient data regarding the area is already available. The plan for either requirement is detailed in the drilling programme for each well.

The services of the contractor shall be provided 24 hours per day in 12 hour shifts.

2       Equipment

It is the responsibility of the contractor to provide on board the rig the mud/data logging unit (as necessary) together with associated sensors in order to provide geological surveillance and on-line data recording and processing.

This equipment shall include:

1) Gas monitoring system including degasser, total gas detected, gas chromatograph with recorder, and hydrogen sulphide (H2S) monitor.

2) Mud monitoring system to automatically and continuously measure and display:

• Mud weight in and out.
• Temperature in and out.
• Mud flow in and out.
• Mud resistivity in and out.
• Pit volume totaliser (PVT) microprocessor system capable of monitoring all pits in any combination and to include audio visual high/low alarms for volume level or rate of change.
• Multi channel recorder.

3) Drilling monitoring system to automatically measure and display:

• Weight on bit.
• Hookload.
• Rotary torque and speed.
• Stand pipe pressure.
• Casing pressure.
• Drilling rate (in metres/feet per hour) independent of the rig depth recorder system.
• Pump stroke counter.

4) Geological and auxiliary equipment to allow a normal formation evaluation service to be performed and including microscope, fluoroscope, drying ovens, chemicals etc.

5) Computer hardware and software used in the logging process, with interfaces to the monitoring systems and provides automatic data collection transfer, processing and recording.

3       Logs and Reports

The following logs and reports shall be prepared by the contractor:

1. Logs

A formation evaluation log prepared to Company requirements of 1:500 in meters. Other scales may be specified by prior notice. The logs shall include:

• Lithological percentage, description and interpretation.
• Visual porosity.
• Drill rate.
• Ditch gas.
• Chromatographic data.
• Cuttings gas.
• Oil fluorescence and descriptions.
• Core intervals and descriptions.
• Mud data.
• Bit data and other relevant engineering data.
• Deviation surveys.
• Other logs which may be requested are:
• Drilling data pressure log.
• Pressure analysis log.
• Temperature data log.
• Wireline pressure log.
• All these logs are up-dated regularly on sepia and paper field prints are available at all times.

2. Tapes, discs and printouts

Full sets of magnetic tapes or discs together with the required number of hard copy printouts and plots are taken.

3. Final well report

After the completion of the well a final well report shall be available from the contractor. This report is prepared at the well site and compiled at the contractors office unless otherwise specified.  This report briefly summarises the geology of the well and highlights any points of geological or engineering significance.