The Log witness has a job which encompasses a number of responsibilities:
- Coordination of all well-related logging activities – pre-job, during the job, and post-job
- Training of any new service company logging engineer on client specific requirements
- Interfacing with the Logging engineer, Operations geologist, Well engineer and Drilling Superintendents
- Pre-job, during the job, and post-job reporting of logging objectives and operations
- Participation in and supervision of on-rig wireline logging operations
After the service company is informed of the upcoming job and a logging crew is selected, a wireline witness is also appointed to cover the job. The log witness is sent the wireline logging program and briefed by the operations geologist or well engineer in the operating company.
The logging witness is considered the leader of the logging service project team consisting of the service company logging engineer, his/her crew and the drilling superintendents on the rig. On board the rig, the initial interactions between the logging witness, drilling superintendents and logging engineer should take place, getting consent on the following issues:
- Logging program and objectives
- What tools are required and what tools are available
- Review and discuss risk assessments and potential safety issues
- Preliminary details of the logging plan including expected start date and time
- Lessons learned from previous wells
The logging crew have to check all their equipment to ensure all the logging tools are in working condition and no equipment required for the job is missing. The logging engineer must report any tool problems or missing equipment to the wireline witness and the drilling superintendents on the rig. At this point, the logging program might undergo refinement through discussions between the operating company and the service company with the logging witness taking on an advisory role. Logging time estimates, log presentations and pre-job well information sheets are also prepared prior to the job starting. Any discrepany in the estimated logging time forecast should be highlighted to the drilling superintendent to aid forward planning and logistics. When the job commences, the wireline witness has responsibilities which include:
- Logging company data acquisition: supervision and quality control
- Data formatting and/or reformatting
- Downhole sample measurements supervision: Formation testing and coring
- Daily job reporting
- Ongoing job risk assessment