Shale gas and hydraulic fracturing (fracking) Q&A

Safety of shale gas drilling and well integrity

The operator is responsible for ensuring the safety of the well and the site. HSE scrutinises the working practices adopted by operators to ensure operators manage and control safety risks, conforming to the requirements of the Health and Safety at Work etc. Act 1974, and the following regulations made under the Act:

The Borehole Site and Operations Regulations 1995 (BSOR) apply to all oil and gas well operations onshore, including shale gas operations. These regulations are primarily concerned with the health and safety management of the site.

The Offshore Installations and Wells (Design and Construction, etc) Regulations 1996 (DCR) apply to all wells drilled with a view to the extraction of petroleum (whose definition includes shale gas) regardless of whether they are onshore or offshore. These regulations are primarily concerned with well integrity.

The Reporting of Injuries Diseases and Dangerous Occurrences Regulations 1995 (RIDDOR) set out a specific set of Wells Dangerous Occurrences in Schedule 2, Part I, that the Well Operator has to report to HSE. Reporting of well incidents enables the HSE Energy Division (ED) to investigate those that would have an effect on well integrity and ensures the Well Operator secures improvements to his operations. These are:

For the drilling process, HSE initially scrutinises the well design for safety and then monitors progress on the well to determine if the operator is conducting operations as planned. An oil and gas well is a complex engineered construction and the key to well integrity inspection is to ensure that the operator is managing risks effectively throughout the life cycle of the well. To ensure this, HSE uses an inspection and assessment process consisting of the following main elements, all of which utilise HSE's experienced specialist wells inspectors:

For new or first time shale gas operators the HSE and Environment Agency will:

For the short-term future, to establish public confidence in the process the HSE/EA intend, as a minimum to:

HSE will also request and review an independent analysis of logging outcomes, used to verify cement job/zonal isolation, during the standard scrutiny of the operator's weekly drilling reports.

Ensuring public safety in the vicinity of fracking sites

The well (borehole) site operator is responsible for ensuring public safety within, and in the direct vicinity of, the work activities, following the industry model code of safe practice. HSE is responsible for regulating this requirement.

Assuring well casing integrity and quality

The integrity of the wells is ensured through a combination of:

Maintaining well integrity

Well design and construction operations follow a recognised industry design and construction process (eg the API Guidance Document HF1 – 'Hydraulic Fracturing Operations – Well Construction and Integrity Guidelines'). Such processes ensure that wells have 'safety features' incorporated into their design. Specific design and construction requirements include:

Cement bond logging and monitoring the integrity of the cement bonding

Cement bond logging (CBL) can be a useful means of verifying integrity where there is a single casing. CBL cannot verify the cement integrity through double casing of pipe and cement. Where there is a double casing, the best method and standard industry practice is to monitor the annular pressures. As an additional protection, the industry is recommending surface methane and groundwater monitoring, with any anomalies to be reported to EA, HSE and DECC, and compared with data from the National Baseline Methane Survey, being undertaken by the British Geological Survey.

Ensuring the quality of concrete well casings

The cement specification, testing of the slurry and placement of it in the well follows recognised industry best practice as contained in the following American Petroleum Institute (API) documents:

Testing well casings

There are a number of tests that operators can use to provide information:

All of the above tests represent standard oilfield practice for well construction and are not particular to shale gas operations.

Casings in the well are typically pressure tested as follows:

Independent monitoring arrangements

Regulation 18 of the Offshore Installations and Wells (Design and Construction, etc) Regulations 1996 requires the Well Operator to set up a Well Examination scheme and appoint a Well Examiner. The Well Examination Scheme and involvement of the Well Examiner is for the complete lifecycle of the well from design through to final plugging and decommissioning. The Well Examiner is an independent competent person who reviews the proposed and actual well operations to confirm they meet the Well Operators policies and procedures, comply with the Offshore Installations and Wells (Design and Construction, etc) Regulations 1996 and follow good industry practice. During assessment and inspection activities, HSE checks that the operator has these arrangements in place.

The Well Operator's well examination scheme requires the operator to send the following documents to his Well Examiner:

The Well Examiner reviews these documents to ensure the complete lifecycle of the well is designed, constructed and operated in line with the Well Operator's policies and procedures, good industry practice and legal compliance.

Shale gas well operators will ask their well examiners to examine certain well integrity and fracturing operations in real time, especially during the early stages of a development, to provide a further level of independent assurance. Such periodic site visits should be made at the discretion of the examiner, in addition to assessing documentary evidence of well integrity, to observe and verify that such operations have been executed satisfactorily in accordance with the approved programme. The frequency and need for such site visits to shale gas operations would reasonably be expected to reduce with time.

Safe use of radioactive sources on site

Radioactive sources are used in oil and gas exploration, but are also extensively used throughout many other industries, including the NHS, paper and steel manufacturing, food irradiation, medical sterilisation and the construction industry. Nuclear well logging tools are robustly built with almost no chance of radioactivity release under normal oilfield operations and stringent regulatory requirements are imposed on the transport, storage, handling, abandonment and eventual disposal of chemical radioactive sources.

International Atomic Energy Agency (IAEA) guidelines, European Union protocols, and national regulatory bodies prescribe standards for the handling of all radioactive sources [IAEA, 2003a; IAEA, 2004; IAEA, 2005; EU, 2009; NRC, 1987; NRC, 1991] to ensure their safe use. The use of ionising radioactive sources in the UK is strictly controlled by the UK radiological regulatory framework, which includes the Ionising Radiations Regulations 1999 enforced by HSE, as well as other legislation enforced by the environmental regulators, Department of Health, and the Office of Nuclear Regulation, all of which have programmes of inspection in place to ensure compliance. Strict security and safety procedures are used for storing these tools and special shielded containers are used for transporting sources. Only authorised personnel following specific rules can access sources of this nature.

In almost all cases nuclear logging tools are owned and operated by oil and gas service companies, who are licensed to use the equipment. Operators would commission service companies to undertake well logging as and when their operations require their use. The use of such sources by appropriately trained personnel in accordance with the prescribed standards will not result in any risk to public health.