Riserless Light Well Intervention
Encyclopedia
Riserless Light Well Intervention (RLWI) enables the petroleum operators to increase the oil and gas recovery rate from subsea
oil well
s. The operation is performed through smaller dynamic positioned
monohull
vessels instead of larger mobile installations like traditional semisubmersible drilling rigs or drillship
s.
The RLWI enable subsea well intervention
without having to use a drilling riser
package connected to the subsea stack (blowout preventer
system).
The technology is based on wireline well maintenance, where the cable is routed via a subsea lubricator system. into the subsea well. Traditional activities are wireline operations for well logging
, perforation
and installing or pulling equipment like plugs and downhole safety valve
inserts. The operational envelope can be extended by use of tractors in horizontal wells
.
The recovery rate has traditionally been considerably lower on a subsea well than for a surface platform
well due more complicated well intervention and maintenance issues. RLWI enables the operators to perform intervention to increase the recovery rate at reduced time and cost.
There is a positive safety aspect by employing RLWI services as no hydrocarbon
s are transported to the vessel, but flushed back into the well through the lubricator system during normal operations. However, RLWI is a complex operation requiring special expertise and control in all phases of the preparation and implementation.
Subsea
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 :...
oil well
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. The operation is performed through smaller dynamic positioned
Dynamic positioning
Dynamic positioning is a computer controlled system to automatically maintain a vessel's position and heading by using its own propellers and thrusters...
monohull
Monohull
rightA monohull is a type of boat having only one hull, unlike multihulled boats which can have two or more individual hulls connected to one another.-Fundamental concept:...
vessels instead of larger mobile installations like traditional semisubmersible drilling rigs or drillship
Drillship
A drillship is a maritime vessel that has been fitted with drilling apparatus. It is most often used for exploratory offshore drilling of new oil or gas wells in deep water or for scientific drilling. The drillship can also be used as a platform to carry out well maintenance or completion work such...
s.
The RLWI enable subsea well intervention
Well intervention
A well intervention, or 'well work', is any operation carried out on an oil or gas well during, or at the end of its productive life, that alters the state of the well and or well geometry, provides well diagnostics or manages the production of the well....
without having to use a drilling riser
Drilling riser
A drilling riser is a conduit that provides a temporary extension of a subsea oil well to a surface drilling facility. Drilling risers are categorised into two types: marine drilling risers used with subsea blowout preventer and generally used by floating drilling vessels; and tie-back drilling...
package connected to the subsea stack (blowout preventer
Blowout preventer
A blowout preventer is a large, specialized valve used to seal, control and monitor oil and gas wells. Blowout preventers were developed to cope with extreme erratic pressures and uncontrolled flow emanating from a well reservoir during drilling. Kicks can lead to a potentially catastrophic...
system).
The technology is based on wireline well maintenance, where the cable is routed via a subsea lubricator system. into the subsea well. Traditional activities are wireline operations for well logging
Well logging
Well logging, also known as borehole logging is the practice of making a detailed record of the geologic formations penetrated by a borehole. The log may be based either on visual inspection of samples brought to the surface or on physical measurements made by instruments lowered into the hole...
, perforation
Perforation (oil well)
A perforation in the context of oil wells refers to a hole punched in the casing or liner of an oil well to connect it to the reservoir. In cased hole completions, the well will be drilled down past the section of the formation desired for production and will have casing or a liner run in...
and installing or pulling equipment like plugs and downhole safety valve
Downhole safety valve
A downhole safety valve refers to a component on an oil and gas well, which acts as a failsafe to prevent the uncontrolled release of reservoir fluids in the event of a worst case scenario surface disaster...
inserts. The operational envelope can be extended by use of tractors in horizontal wells
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...
.
The recovery rate has traditionally been considerably lower on a subsea well than for a surface platform
Oil platform
An oil platform, also referred to as an offshore platform or, somewhat incorrectly, oil rig, is a lаrge structure with facilities to drill wells, to extract and process oil and natural gas, and to temporarily store product until it can be brought to shore for refining and marketing...
well due more complicated well intervention and maintenance issues. RLWI enables the operators to perform intervention to increase the recovery rate at reduced time and cost.
There is a positive safety aspect by employing RLWI services as no hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
s are transported to the vessel, but flushed back into the well through the lubricator system during normal operations. However, RLWI is a complex operation requiring special expertise and control in all phases of the preparation and implementation.