Well integrity
Encyclopedia
Well integrity, in regards to oil well
s, is defined by 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.
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.
. 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
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
.
) equipment. The wellhead
and the tree
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.
Oil well
An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
s, is defined by 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.
Accountability/responsibility
Accountability is the position that ensures a particular task is being done. They typically control the budget and organizational chartOrganizational chart
An organizational chart is a diagram that shows the structure of an organization and the relationships and relative ranks of its parts and positions/jobs...
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
Well services
Well services is a department within a petroleum production company through which matters concerning existing wells are handled. Having a shared well services department for all assets operated by a company is seen as advantageous as it allows the pooling of talent, experience and resources for...
, 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 tubingProduction tubing
Production tubing is a tube used in a wellbore through which production fluids are produced .Production tubing is run into the drilled well after the casing is run and cemented in place. Production tubing protects wellbore casing from wear, tear, corrosion, and deposition of by-products, such as...
. 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
Casing (oil well)
Casing is large diameter pipe that is assembled and inserted into a recently drilled section of a borehole and typically held into place with cement.-Purpose:Casing that is cemented in place aids the drilling process in several ways:...
, which bound the annuli
Annulus (oil well)
The annulus of an oil well refers to any void between any piping, tubing or casing and the piping, tubing, or casing immediately surrounding it. It is named after the corresponding geometric concept...
. 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
Gas lift is one of a number of processes used to artificially lift oil or water from wells where there is insufficient reservoir pressure to produce the well. The process involves injecting gas through the tubing-casing annulus. Injected gas aerates the fluid to reduce its density; the formation...
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
MAASP
Maximum Allowable Annulus Surface Pressure is an absolute upper limit for the pressure in the annulus of an oil and gas well as measured at the wellhead.-Background:...
.
Tree and wellhead integrity
This refers to the integrity of the surface (or subseaSubsea
Subsea is a general term frequently used to refer to equipment, technology, and methods employed in marine biology, undersea geology, offshore oil and gas developments, underwater mining, and offshore wind power industries.- Oil and gas :...
) equipment. The wellhead
Wellhead
A wellhead is a general term used to describe 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....
and the tree
Christmas tree (oil well)
In petroleum and natural gas extraction, a Christmas tree, or "tree", is an assembly of valves, spools, and fittings used for an oil well, gas well, water injection well, water disposal well, gas injection well, condensate well and other types of wells...
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.