This study will fundamentally center on how the followerss – Subsea Completions and Workover, Subsea Trees and Subsea Processing are applied to maximise oil production in the Gulf of Mexico.
Well completion involves the installing of a production conduit into which has been incorporated assorted constituents to let efficient production, force per unit area unity proving etc [ 2 ] .
Workover -The recompletion of the well to reconstruct production or alter the well map [ 2 ] or the procedure of replacing and care operations on the tools in an oil or gas good.
A subsea tree, besides called a “ wet tree, is an assembly of control valves, gages and choking coils that control oil and gas flow in a completed well ” [ 2 ] . The tree besides enables methyl alcohols and chemical injection, force per unit area and temperature monitoring and allows perpendicular entree for intercession [ 2 ] .
The remotion of unwanted components and recovery wanted components is called procedure of hydrocarbon under a status of force per unit area and temperature. Subsea processing is the processing of hydrocarbon fluids on the ocean floor. Procedures of these subsea processing involved include H2O re-injection, multiphase boosting, stage separation gas compaction. Not all procedures are done offshore ; some are still designed for onshore processing.
The Gulf of Mexico part is the arm of the Atlantic Ocean and is bound on the nor’-east, North and Northwest by the Gulf seashore of the United States, on the sou’-west and South by Mexico, and on the sou’-east by Cuba [ 3 ] . In this part, completions and workovers, subsea trees and subsea processing have been designed to make a peculiar undertaking. The Gulf of Mexico is amply able with hydrocarbon sedimentations in deepwater. Below is a image demoing the Gulf of Mexico and the states around the part.
The Gulf of Mexico [ 4 ]
Subsea Well Completion involves all the work done on the well prior to production and the installing of subsurface equipment e.g. tubing hanger, blow out preventer ( BOP ) , etc in order to successfully bring forth from the well. Completion consists of the lower and upper completion procedures. The upper completion involves installing of all the assorted constituents from the base of the production tubing right to the top, while lower completion takes topographic point around the production country. Some classs of lower completions are:
2.1 Barefoot Completion: This type of completion is suited for difficult stone, multilerals and under balance boring. Not suited for weaker formations necessitating sand control and Wellss that require selective isolation of oil, gas and H2O intervals [ 5 ] .
Barefoot completion [ 8 ]
2.2 Cased Hole Completion: The part of the wellbore that has had metal casing placed and cemented to protect the unfastened hole from fluids, force per unit areas, wellbore stableness jobs or a combination of these. This is besides the procedure whereby a shell is run down through the production zone and cemented in topographic point. This type of completion encourages good control of fluid flow [ 5 ] .
Cased hole completion [ 7 ]
2.3 Open Hole Completion: This type of completion is more advantageous in horizontal Wellss because the proficient enlistments and the high cost of cemented line drives is associated with horizontal Wellss [ 5 ] .
The simplest types of oil well or gas good completion, unfastened hole completions have several restrictions and disadvantages. Consequently, they are typically limited to particular completions in formations capable of defying production conditions [ 6 ] .
Open hole completion [ 6 ]
2.4 Components normally used in subsea well completions include:
Punching Guns: This type of constituent is used to make predefined form of perforation in the sides into the reservoir by agencies of explosive charges, to let the flow of oil into the well [ 9 ] . An illustration is shown below.
Punching gun [ 9 ]
2 Wellhead: This is the chief constituent that houses the valves that controls fluid from the well to the manifold. It besides acts as an interface between the production installation and the reservoir.
Wellhead [ 10 ]
Tubing Hanger: This constituent is located on the top of the manifold provides support for the production tube. See image below.
Tubing Hanger [ 11 ]
Production Packer: “ This is a standard constituent of the completion hardware of oil and gas good and it is a seal between the tube and the shell. It is used to insulate one portion of the ring from another for assorted grounds ” . This is done to divide different subdivisions like the gas lifts subdivision from the production subdivision. It is besides used in injection Wellss to insulate the zones. [ 12 ] .
Production paker [ 2 ]
Production tube: This is the basic channel through which hydrocarbon flows from the reservoir to the surface. The diagram is seen below.
Production Tubing [ 13 ]
Downhole Safety Valve: This is used to protect the surface from the uncontrolled release of hydrocarbons. It is a cylindrical valve with either a ball or flapper shutting mechanism ; it is installed in the production tube and is held in the unfastened place by hydraulic force per unit area from surface [ 5 ] . See the diagram below.
Downhole Safety Valve [ 14 ]
6 Annular Safety Valve: This is needed to insulate the production tube in order to
prevent the stock list of natural gas downhole from going a jeopardy. See the diagram below.
Annular Safety Valve [ 15 ]
Landing Nipples: This is a receptacle to have wireline tools. It is besides a utile marker for deepnesss in the well, which can be hard to accurately find as you can see in the diagram below [ 4 ] .
Landing Nipples [ 16 ]
Downhole Guages: This is an electronic or fibre ocular detector to supply uninterrupted monitoring of downhole force per unit area and temperature. Gauges use a 1/4 ” control line clamped onto the exterior of the tubing twine to supply an electrical or fibre ocular communicating to come up as shown in the diagram below.
Downhole Guage [ 17 ]
Wireline Entry Guide: This constituent is frequently installed at the terminal of the tube ( the shoe ) . It is intended to do drawing out wireline tools easier by offering a guiding surface for the tool threading to re-enter the tube without acquiring caught on the side of the shoe.The diagram is shown below [ 5 ]
Wireline entry usher [ 18 ]
Centralizer: In extremely deviated Wellss, this constituent may be included towards the pes of the completion. It consists of a big neckband, which keeps the completion twine centralised within the hole [ 5 ] .
Centralizer [ 19 ]
Mensa field is an illustration of completions in the Gulf of Mexico. It consists of three Wellss and gathers gas into a manifold and transports it to West Delta 143 platform 68 stat mis. See the diagrams below [ 20 ] .
Subsea development [ 20 ] Subsea Production manifold [ 20 ]
Well Performance Sensitivities [ 2 ]
“ Reduced production, graduated table, tubing and constituents leaks, unreal lift failures e.g. ESP failure, H2O shut off and re-perforation, alteration of good map e.g. manufacturer to injector are some events needed for workover operation on a well ” [ 2 ] . “ A brief sum-up of the completed workovers in the Gulf of Mexico are:
A-10: Cleared dust and zone was re-perforated. Initial production 140bopd with 10/64 choking coils. Well continues to bring forth at a rate of 140 bopd.
A-2: Cleared dust and oil flowed to the surface followed by emulsions. Presently, the well is being analyzed to find the appropriate solution needed to liquefy the emulsions so that the well can flux without break.
A-16: Cleared dust and re-perforated. Well did non bring forth from bing zone. Currently under analysis to find if other zones can be considered as campaigners for perforation ” [ 21 ] .
4.0 SUBSEA TREES
This can be classified into three types based on tree Configuration, tree functionality and
Schematic of the subsea tree [ 22 ]
4.1 Tree Configuration
The undermentioned below are the characteristics of a horizontal tree
– “ The valves are set off to the side.
– Well intercession can be done through them.
– No valves in the perpendicular dullard
– Tree tally before the Tubing Hanger
– Tube Hanger Easts from Tree ( Passive )
– Internal Tree Cap installed
– Tube Hanger seals are exposed to good fluids ” [ 23 ]
Horizontal Tree [ 24 ]
Conventional Dual Bore ( Vertical ) Trees
Below are the characteristics of a double dullard tree:
– “ Master & A ; Swab valves in perpendicular dullard
– Tree tally after Tubing Hanger
– Tube Hanger Easts from Wellhead or BOP pin ( Active )
– External Tree Cap installed
– Tube hanger seals isolated from good fluids ” [ 23 ]
Conventional Dual Bore Tree [ 24 ]
A 3rd type is the Mudline tree. These are normally used for shallow H2O applications and typically installed from jack-up rigs. They have minimum hydraulic maps [ 24 ] .
4.2 Tree Functionality
Trees by and large can either be used on production Wellss or on injection Wellss. Therefore we have
4.3 Tree Installation Pattern
Trees can be installed either with Guidelines or Without Guidelines.
Examples of installed subsea trees in the Gulf of Mexico are:
Enhanced Vertical Deepwater Subsea Tree ( EVDT ) produced by FMC engineerings
This was used at the Shell-operated Silver tip field, portion of the Perdido Development located to put a current subsea deepwater completions record of 9,356ft [ 25 ] .
Enhanced Deepwater Subsea Tree [ 26 ]
Gyrfalcon Subsea Tree
This was the universe ‘s first 15,000psig subsea tree. The tree was adapted by Cameron from an bing mono-bore mudline tree, with modified constituents from its 10,000psig tree design [ 27 ] .
Gyrfalcon Subsea Tree [ 27 ] During Installation [ 27 ]
Enhanced Horizontal Xmas Tree ( EHXT )
This was to be supplied by FMC in the Blind Faith Development which is located in about 7,000ft of H2O [ 28 ] .
15k Enhanced Horizontal Tree [ 28 ]
Conventional Dual Bore Trees used in Troika Field.
Troika oil field, located 150 stat mis offshore Louisiana in Green Canyon 244 unit and lies in H2O deepness of 2700ft made usage of conventional, non-TFL, 10,000psi double bore 4inA-2in constellation, installed utilizing guidelines [ 29 ]
“ Deployment of subsea treating systems has seen a pronounced acceleration in the past twosome of old ages, with assorted separation and hiking systems being ordered for deployment in the North Sea, the Gulf of Mexico, West Africa, South America and Australia ” [ 30 ] . A impulsive factor for this is cost. Cost decrease is obvious when big and expensive topside installations are eliminated for the subsea 1s. Other drivers include “ flow direction and flow confidence, accelerated and or increased recovery, development of disputing subsea Fieldss ” [ 31 ] . Deployments in the Gulf of Mexico include:
Submerged Production System [ 32 ]
Aker Kvaerner ‘s MultiBooster System
“ The start-up of Aker ‘s MultiBooster pump engineering at a H2O deepness of 5,500ft below surface is expected to hike BP ‘s production at the King Field by an norm of 20 % . The MultiBooster system is a subsea multiphase pump faculty, uniting field-proven twin screw engineering with Aker ‘s suite of processing and subsea engineering ” [ 33 ] .
Aker Kvaerner ‘s MultiBooster [ 33 ]
FMC Subsea Caisson Separation and Boosting System
Besides in the Perdido development, FMC ‘s range of work included the supply of subsea coffer separation and hiking system [ 34 ] . The gas/liquid coffer centrifuges with ESPs where used because of the Fieldss low reservoir force per unit area and heavy oil [ 31 ] .
Gas/Liquid Caisson centrifuge at 2500m/8200ft H2O deepness
for the Perdido Project [ 31 ]
Subsea engineering and development in the Gulf of Mexico has improved for ages, this is a consequence of conveying new invention to travel the industry frontward and optimise the abundant natural resources beneath the deep H2O and different engineerings involved. This besides makes production activities and geographic expedition and in this part to be more fruitful for both operators every bit good as the sellers.