Well tests and monitoring

Testing well casings

There are a number of tests that operators can use to provide information on the integrity of the well:

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:

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 and so is one of a number of well integrity tests that will be conducted on the well. Where there is a double casing, the best method and standard industry practice is to monitor the annular pressures. As an additional protection, the EA require 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 cement and placement of it in the well follows recognised industry best practice as contained in UKOOG Shale gas Guidelines and the following American Petroleum Institute (API) documents:

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. This is an important quality control mechanism for the industry.

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 regulations 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 requirements.