Basis of reporting

For all health and safety data and most of the environmental data, we use the definitions set by the Association of Oil and Gas Producers (OGP) to guide our reporting requirements and this ensures an accurate benchmark against credible industry data. OGP defines all the incident criteria and operations or contracts which should be included.

Environment

The reported environmental data comes from all Tullow production and exploration operations where Tullow is the operator of the facility or asset during the year. Full details of operated and non-operated facilities are available on pages 154 to 157 of the Annual Report and Accounts 2010.

The main focus of this data is atmospheric emissions. The methodologies utilised in calculations are approved by the UK Oil and Gas atmospheric emissions workgroup and are based upon American Petroleum Institute and US Environmental Protection Agency practices. Comparability of data from year to year may be affected by changes in the methodology, number of facilities, and planned vs unplanned operations. Where year on year comparability has been materially impacted by one or more of these factors, this is made clear in the Report. There is also potential for local interpretation of reporting guidelines to influence uncertainty of data although this is minimised through providing guidelines and definitions as well as through communication with the business units concerned.

Drilling is part of the exploration and production (E&P) life cycle to produce a hole to determine the presence of hydrocarbons by exploration drilling and the extent of the hydrocarbons through appraisal drilling and completion activities. Production drilling provides sufficient coverage across the oil or gas field to ensure the hydrocarbons are efficiently recovered.

Well testing proves or tests the long term commercial capability of a well or field to produce hydrocarbons over a predetermined period with sufficient self generating pressure.

Production is the recovery of oil or gas on a commercial scale for a prolonged period (years) usually defined by a Production Sharing Agreement (PSA). Emissions reported under this include data from the installation involved in the production operations.

Health and Safety

The reported health and safety data are gathered from all sites where Tullow operates and includes production, drilling, seismic and construction activities as well as the office environment. All contractors such as drilling and seismic companies and the associated subcontractors are included in our data as they operate under our management system.

OGP sets a standard regarding the categorisation of all safety incidents and occupational health conditions and we adhere to this position.

Social

The reported social data are gathered from all sites where Tullow operates and includes all permanent local, expatriate employees and contractors working at sites and offices. Staff at all Tullow locations are included for the basis of HR Headcount reporting even if in a few locations Tullow has no operations (e.g. US, Singapore, Senegal, Nairobi). The numbers reconciled in the Social data are the numbers from monthly HR headcount report received from all Tullow locations.

A summary of the criteria and definitions used to record our data is listed below:

Environment

Indicator	Description	Basis of calculation	Unit of measure
Carbon dioxide (CO2)	Gas that contributes to the phenomenon known as the greenhouse effect	Group wide emissions for drilling, well testing and production are calculated using conversion factors sourced from EEMS (Emissions Estimation and Monitoring System), which allows the calculation of emissions where direct monitoring is not undertaken. It involves the use of an activity factor i.e. fuel consumption, flow rate to vent or flare, and an emissions factor, which can be based on direct gas compositional analysis or industry standards.	Tonnes
Methane (CH4)	Gas that contributes to the phenomenon known as the greenhouse effect	Methane emissions are calculated as above for CO2.	Tonnes
Water usage	Quantity of fresh water utilised during operations.	Direct meter readings or daily report data.	Cubic metres
Oil and chemical spills (> 50 litres)	Accidental or unplanned release of oil or chemicals to the environment.	Estimated tonnes discharged.	Absolute number of spills (over 50 litres) Tonnes of oil and/or chemical spilled (N.b. Where 'trace' is used, this indicates a total spill amount of less than 10 litres).

Health & Safety

Indicator	Description	Basis of calculation	Unit of measure
Fatality	Death of a company or contract employee due to a work related incident or illness. "Delayed" deaths that occur after the incident are included if the deaths were a direct result of the incident e.g. if a fire killed one person outright, and a second died three weeks later from lung damage caused by the fire, both are reported.	OGP definitions and methodology	Absolute number of fatalities
3rd Party Fatality	Incident resulting in the death of a 3rd party, who is not employed by Tullow Oil or a Tullow Oil contractor.	OGP definitions and methodology	Absolute number of fatalities
High Potential Incident (HiPo)	An incident where the potential severity is deemed to be High. The actual severity of the incident may be lower than the potential severity providing a powerful learning tool.	Tullow Oil Incident Reporting System incident potential matrix.	Potential severity of incident.
Lost Time Injury (LTI), Lost Time Injury Frequency Rate (LTIFR)	Any work related injury, other than a fatal injury, which results in a person being unfit for work on any day after the day of occurrence of the occupational injury. "Any day" includes rest days, weekend days, leave days, public holidays or days after ceasing employment.	OGP definitions and methodology	LTI: absolute number of injuries LTIFR: number of LTIs per million man hours worked.
Hours worked	All hours worked by employees and contractors.	OGP definitions and methodology, calculated from days worked.	Hours
Medical Treatment Case (MTC)	A work-related injury or illness that results in medical treatment beyond first aid, but that did not involve death (fatality), one or more days away from work (LTI), or one or more days of restricted work (RWDC) i.e. remained at work and was not transferred or restricted.	OGP definitions and methodology	Absolute number of injuries
Near Miss (NM)	An incident which occurs through failure of the management system or equipment that in other circumstances would or could have caused a fatality, LTI, or other such injury. Includes environmental near miss or other incident that could have caused damage to assets or company reputation.	OGP definitions and methodology	Absolute number of incidents
Restricted Work Day Case (RWDC)	Any work-related injury other than a fatality or lost work day case which results in a person being unfit for full performance of the regular job on any day after the occurrence of the occupational injury. Work performed might be: an assignment to a temporary job; part-time work at the regular job; continuation full-time in the regular job but not performing all the usual duties of the job. Where no meaningful restricted work is being performed, the incident is recorded as a Lost Time Incident.	OGP definitions and methodology	Absolute number of injuries
Total Recordable Injuries (TRI), Total Recordable Injuries Frequency Rate (TRIFR)	The sum of all fatalities, LTIs, RWDCs, and MTCs excluding occupational illness.	OGP definitions and methodology	TRI: Absolute number of injuries TRIFR: number of TRIs per million man hours worked.

Social Data

Indicator	Description	Basis of calculation	Unit of measure
Number of employees	Total number of permanent local staff and permanent resident expatriate staff paid directly by Tullow.	HR Records	Absolute number
Number of contractors	Total number of Tullow contractors those who are under a work order / purchase order, work on a fixed day rate and on rotating work patterns. They are equivalent FTEs but paid differently than employees. Third party agency workers, consultants or temporary workers are not included.	HR Records	Absolute number
Number of expatriate employees	Total number of employees working for Tullow in a country other than their home country including employees on secondment.	HR Records	Absolute number
Number of local nationals	The total number of employees working for Tullow in the country in which they are resident.	HR Records	Absolute number
Number of female employees	Total number of employees and contractors who are female.	HR Records	Absolute number
Number of female managers	Total number of managers who are female. A manager is any individual who has responsibility for direct line reports.	HR Records	Absolute number
Total workforce	Sum of employees and contractors. Also sum of expatriate employees and local nationals.	HR Records	Absolute number

Further definitions used in the Report are:

Biodiversity

Variety of organisms found within a specified geographic region.

Hydrocarbon

A compound containing only the elements hydrogen and carbon. May exist as a solid, a liquid or a gas. The term is mainly used in a catch-all sense for oil, gas and condensate.

Social and Community

The Social and Community metrics relate to all parts of our business. We report our Social Enterprise spend in US$.

Non Operated Activity

In line with the OGP definitions, Tullow only reports the environmental, health and safety data where Tullow is the operator of the exploration or production facility. Non operated EHS data is not included in the report.

Independent Assurance

Deloitte LLP (Deloitte) has provided limited assurance on the group compilation process of selected environmental, health CSR expenditure and safety data as set out by them in their assurance statement, which is reproduced in the Report. See the independent assurance report.