Well integrity, in regard to

oil well An oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may ...

s, is defined b
NORSOK D-010
as the "“Application of technical, operational and organizational solutions to reduce risk of uncontrolled release of formation fluids throughout the life cycle of a well”. There are various facets to well integrity, including accountability/responsibility, well operating processes, well service processes, tubing/annulus integrity, tree/wellhead integrity and testing of safety systems. A similar form of words are used in ISO 16530 well integrity standard

Accountability/responsibility

Accountability is the position that ensures a particular task is being done. They typically control the budget and

organizational chart An organizational chart, also called organigram, organogram, or organizational breakdown structure (OBS) is a diagram that shows the structure of an organization and the relationships and relative ranks of its parts and positions/jobs. The term ...

structure. Responsibility is the position that actually does the task. There are a variety of tasks associated with well integrity and responsibility can reside with a field's well operations engineer, operators, well service technicians, etc.

Well operating processes

This includes processes such as personnel competency, well startup-operating-shutdown procedures, process to report anomalies, corrosion/erosion control, etc.

Well service processes

This includes processes such as personnel competency, intervention procedures, etc.

Tubing/annulus integrity

This refers to the integrity of the

production tubing Production tubing is a tube used in a wellbore through which production fluids are produced (travel). Background Production tubing is run into the drilled well after the casing is run and cemented in place. Production tubing protects wellbore cas ...

. Common threats to tubing integrity are erosion and corrosion by production fluids, which denude the steel. The other threat is pressure differential between the tubing and the 'A' annulus. If it exceeds the rated pressure of the tubing, there is a risk of tubing burst or tubing collapse. This refers to the integrity of the casing strings, which bound the annuli. All annuli will naturally be filled to some level with brine or other fluids from the completion, though the 'A' annulus may have gas down to the lowest gas lift valve if the well is

gas lift Gas lift or bubble pumps use the artificial lift technique of raising a fluid such as water or oil by introducing bubbles of compressed air, water vapor or other vaporous bubbles into the outlet tube. This has the effect of reducing the hydrostati ...

ed. The major integrity issues comes from the differential pressure across the casings due to the weight of brine on either side. To protect well integrity, each annulus will have a Maximum Allowable Annulus Surface Pressure.

Tree and wellhead integrity

This refers to the integrity of the surface (or

subsea Subsea technology involves fully submerged ocean equipment, operations, or applications, especially when some distance offshore, in deep ocean waters, or on the seabed. The term ''subsea'' is frequently used in connection with oceanography, marin ...

) equipment. The

wellhead A wellhead is the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment. The primary purpose of a wellhead is to provide the suspension point and ...

and the

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

are typically suitably engineered to be able to withstand the normal operating pressures. The major integrity issues for these components surround the operation of the valves, which are prone to leaking. For this reason, valves must be routinely maintained.

Testing of safety systems

This refers to testing of surface and subsurface safety systems. {{DEFAULTSORT:Well Integrity Oil wells