Completion Design(#2)

Petroleum Engineering Department “Completion Design” Lecture #2

Barham S. Mahmood [email protected]

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Outline Introduction

Completion Design Considerations Bottom-hole Completion Techniques

Selection of Production Conduit Completion String Facilities

Completion String Components Factor affecting on well completion designs

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Introduction  After exploratory drilling confirms the presence of an oil or natural gas reservoir, the hydrocarbons are brought to the surface.  Once the design well depth is reached, the formation is tested and evaluated to determine whether the well is to be completed for production, or plugged and abandoned.  This decision is taken based on the information available on reservoir characteristics.  To complete the well production, casing is installed and cemented, and the drilling rig is dismantled and moved to the next site.  A service rig is brought in to perforate the production casing and run production tubing along with downhole equipment.

 The installation of surface safety equipment takes place and production begins.

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What is well completion?  Well completion creates a dependable pathway to the surface for the hydrocarbons.

 Once the well is drilled, it has to be made ready for the safe and efficient production of oil.  The term ‘completion’ describes the assembly of Down hole tubulars and other safety equipment that is required to enable the safe and efficient production of oil or gas from the well after it has been drilled.

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Generally completion process consist of: a) A method of providing satisfactory communication between the reservoir and the borehole. b) The design of the tubulars (casing and tubing) which will be installed in the well. c) An appropriate method of raising reservoir fluids to the surface. d) The design, and the installation in the well of various components used to allow efficient production, pressure integrity testing, emergency containment of reservoir fluids, reservoir monitoring, barrier placement, well maintenance and well kill.

e) The installation of safety devises and equipment, which will automatically shut a well in the event of a disaster.

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Before knowing the classification of completion, must know the main objective from wells drilling as following: 1- Exploration and evaluation wells This type of wells is drill for exploration and evaluation. 2- Production wells The wells are drilled and completed for produce oil, gas and sometime water produce.

3- Injection wells The wells are drilled and completed for inject water or gas or chemical material and sometimes petroleum products.

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4- Measurement and observation wells The wells are drilled and completed for observation the reservoir (reservoir fluid behavior, reservoir pressure, etc...).

5- Special operation wells The wells are drilled and completed for special operation such as to kill the below out well.

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Completion Design Considerations  Before a production well is drilled, a great deal of planning must be undertaken to ensure that the design of the completion is the

best possible.  A number of factors must be taken into consideration during this planning stage, which can broadly be split into: a) The objective of well drilling

b) Reservoir considerations and c) Mechanical considerations

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a) Objective of well drilling  The objective of well drilling is very important factor in well completion design, may be the purpose from well drilling is clear from beginning or changed with time.  A certain well completed as producing well then after that convert to injection well or observation well depend on the reservoir conditions.

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b) Reservoir considerations Its include the following factors

1. Natural rock reservoir The geological and experimental studies that conduct to delineate the nature of rock reservoir (type of rock, including fault, reservoir permeability, etc…) is important to select the adequate completion design.

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2. Producing rate To provide maximum economic recovery is often the starting point for well completion design. Among other factors producing rate should determine the size of the producing conduit. 3. Multiple reservoirs Multiple reservoirs penetrated by a well pose the problem of multiple completions in one drilled hole. Possibilities include multiple completions inside casing separated by packers, or several strings of smaller casing cemented in one borehole to provide in effect separate wells. Other possibilities include coming of hydrocarbons from separate reservoir downhole, or drilling several boreholes from one surface location.

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4. Reservoir drive mechanism Reservoir drive mechanism may determine whether or not the

completion interval will have to be adjusted as gas-oil or water-oil contacts move. A water drive situation may indicate water production problems. Dissolved gas and gas drive reservoirs usually mean declining productivity index and increasing gas-oil ratio.

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5. Secondary recovery requirements Secondary recovery needs may require a completion method conductive to selective injection or production. Water flooding may increase volumes of fluid to be handled. High temperature recovery processes may require special casing and casing cementing materials.

6. Stimulation Stimulation may require special perforating patterns to permit zone isolation, perhaps adaptability to high injection rates, and a well hookup such that after the treatment the zone can be returned to production without contact with killing fluids.

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7. Sand control Sand control problems alone may dictate the type of completion method and maximum production rates. On the other hand, reservoir fluid control problems may dictate that a less than desirable type of sand control be used.

8. Artificial lift Artificial lift may mean single completions even where multiple zones exist.

9. Workover requirements Workover frequencies, probably high where several reservoirs must be drained through one wellbore, often dictate a completion conducive to wireline or through-tubing type recompletion systems.

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c) Mechanical considerations  The mechanical configuration or "well hookup" is often the key to being able to deplete the reservoir effectively, monitor downhole performance, and modify the well situation when necessary.  The mechanical configuration of the well is the key to being able to do what ought to be done in the well from the standpoint of controlling the flow of reservoir fluids, oil, gas, and water.

• • • • •

Functional requirements Operating conditions Component design Component reliability Safety

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Completion Methods  Wells can be producers or injectors.  Completions can produce oil, gas and water.  Completions can inject hydrocarbon gas, water, steam and waste products such as carbon dioxide, sulphur, hydrogen sulphide, etc.  More than one purpose can be combined either simultaneously (e.g. produce the tubing and inject down the annulus) or sequentially (produce hydrocarbons and then convert to water injection duty).

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Conceptual Design Principal decision areas are:

Bottom hole completion technique Selection of Production Conduit

Completion String Facilities Completion String Components

23”-27” bit for drilling 18-5/8” casing Cementing 17-1/2” bit for drilling 13-3/8” casing Cementing 12-1/4” bit drilling 9-5/8” casing Cementing Drilling, if necessary 7”liner and cementing, or…

30” conductor pipe

18-5/8” casing

13-3/8” casing

9-5/8” casing

Bottomhole Completion

7” liner Produce formation

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Bottomhole Completion Techniques 1. Open Hole Completion The production casing is set on top of production zone before drilling the

production formation that contains the hydrocarbon fluids, and then after casing was cemented, producing formation drilled.

Production casing

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Advantages 1. Adaptable to special drilling techniques to minimize formation damage or to prevent lost circulation into the production zone (cement loss) 2. No perforating expense 3. Log interpretation is not critical since entire interval is open ( open hole relogging is possible) 4. Full diameter of pay zone 5. Can be easily deepened

6. Easily converted to liner or perforated completion (or other types of completion) 7. With gravel pack provides excellent sand control

8. Require minimum rig time on completion

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Limitations 1. Excessive gas and water production difficult to control (gas and water coning ) 2. Selective critical section in production zone for fracturing or acidizing more difficult 3. May require frequent well-bore cleanout

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2. Cased Hole Completion The production casing is cemented through producing zone and perforated

Advantages

Production casing

1. Excessive gas or water production can be controlled more easily. 2. Can be selectively stimulated. 3. Log and formation samples available to assist in decision to set casing or abandon

Perforation

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4. Full diameter opposite pay. 5. Can be easily deepened.

6. Will control most sand, and is adaptable to special sand control techniques.

7. Adaptable to multiple completion techniques. 8. Minimum rig time on completion.

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 Limitations 1. Cost of casing cement and perforating for long zones may be significant. 2. No adaptable to special drilling techniques to minimize formation damage. 3. Log interpretation is critical for most of logs except production logging.

4. Well productivity is less than productivity of open-hole well completion.

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3. Perforated completion This is divided into:A. Screen and Liner completion B. Perforated Liner completion

Production casing

C. Slotted liner completion

A. Screen and Liner completion The production casing is set on top of producing zone, than the screen and the liner is set through producing zone

Screen and liner assembly

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 Advantages 1. Adaptable to special drilling techniques to minimize formation damage or to prevent lost circulation into the producing zone. 2. No perforating expense. 3. Log interpretation is not critical since entire interval is open

4. Do not require frequent well-bore cleanout. 5. Will control most sand, and is adaptable to special sand control techniques.

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 Limitations 1. Excessive gas or water production difficult to control.

2. Selective critical section in production zone to fracturing or acidizing more difficult.

3. Wellbore deepened is not easy. 4. Requires more rig time on completion

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B. Perforated Liner completion The production casing is set on top of

producing zone, then the producing

Production casing

zone was drilled after that the liner is set

and cemented through producing, then perforated Liner Perforation

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 Advantages 1. Adaptable to special drilling techniques to minimize formation damage or to prevent lost circulation into the producing zone. 2. Gas and water production easy to control. 3. Selective critical section in production zone to fracturing or acidizing more easy. 4. Can be easily deepened.

5. Will control most sand because the liner obstructed sand movement, and is adaptable to special sand control techniques

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 Limitations 1. Cost of casing cement and perforating for long zones may be significant. 2. Log interpretation is critical for most of logs.

3. Requires more rig time on completion. 4. Difficult conduct good cement operations for liner compare with

the first stage of casing cementing

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C. Slotted liner completion The production casing is set on top of producing zone, then the producing zone was drilled after that the slotted liner is set  Slot or screen gauge is simply the width of the opening in inches multiplied by 1,000

For instance  A 12-gauge screen has openings of 0.012 in. Routine slot widths are 0.030 in. or larger.

 The minimum slot width that can be achieved is about 0.012 in.

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 Advantages 1. No perforation and cementing cost

2. Adaptable with gravel pack sand control (can be used together) 3. Can be easily changed

 Limitations 1. Control of gas and water production is not easy 2. Selective stimulation is difficult (Zonal isolation is impossible)

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Conceptual Design Principal decision areas are:

Bottom hole completion technique

 Selection of Production Conduit

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Selection of Production Conduit  Tubingless casing flow  Casing and tubing flow

 Tubing flow without annular isolation

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 Casing flow without annular isolation  Tubing flow with annular isolation



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Basically there are two tubular configuration methods of completing a well: 1- Conventional tubular configuration  Single zone completion  Multiple zone completion 2- Unconventional tubular configuration

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Conventional tubular configurations The conventional completions methods consist of production casing have outside diameter grater than 4 ½ inch, and include;

1- Single-zone completion Factors leading to selection of single-zone “conventional” completions:  High production rates.

 Corrosive well fluids.  Operator tradition.

 High pressures governmental policies.

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 Probability of well competition for single-zone depending on objectives from well drilling, and that include: A. Well produce through production casing This type of completion use in wells produce with high production rates and medium or low closed, flowing pressures.

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B. Well produce through production casing and production tubing  In this type of completion the well produce through annulus and tubing in same time.  the production rate in this type being less than in type of producing through production casing.

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 Valid reasons for tubing may include: 1) Better flow efficiency. 2) Permit circulation of kill fluids, corrosion inhibitors or paraffin solvents. 3) Provide multiple flow paths for artificial lift system. 4) Protect casing from corrosion, abrasion, or pressure.

5) Provide indicate of monitoring bottom-hole flowing pressure.

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C. Well produce through production tubing  The well completed by using tubing and single production packer

 In this completion the maximum potential of well to produce by high flow rate impossible, compare with the well produce through production casing and the well produce through production casing and production tubing.

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 A packer should be run only where it accomplishes a valid objective such as:

1) Improve or stabilize flow. 2) Protect casing from well fluids or pressure however, it should be recognized that use of a packer may increase pressure on casing in the event of a tubing leak. 3) Contain pressure in conjunction with an artificial lift system or safety shut-in system. 4) Hold on annular well-killing fluid.

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D. Well produce by pumping In this type the well produce by pumping, where the tubing run in hole with pump seating nipple to depth below working fluid level in well

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E. Gas lift well This type used in wells drilled in formations have low pressure (formation pressure could not rises the fluids to surface), where the gas injected through annulus and by special lift mandrel (Valve), the gas inter inside tubing , that help to rise the oil to surface through tubing by reduce the weight of oil column (fluid hydrostatic pressure).

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Conventional tubular configurations 2- Multiple-zone completion

Factors leading to selection of multiple completions:  High producing rate

 Faster payout  Multi-reservoir control equipment's

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 Numerous configurations are possible utilized single or multiple strings of tubing: A. Single-well with alternate completion

B. Dual completion-single packer, single tubing string C. Cross-over dual completion –single tubing

D. Parallel dual packer completion E. Parallel dual packer with two alternate completions

F. Triple completion

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1. Single-well with alternate completion  This type is used when the well penetrate two producing formations. Isolated by using dual production packer, the alternate formation started to produce after the lower producing formation stopped producing.  Blast joint used in tubing part in front of alternate producing formation to resist the erosion that cause by produce fluids, because the blast joint have thick wall

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2. Dual completion-single packer, single tubing string There is both tubing and annulus flow. This is the lowest cost conventional dual Completion

Limitations  Upper zone cannot be produced through tubing, unless lower zone is blanked off.  Casing subject to pressure and corrosion.  Only lower zone can be artificially lifted.  Upper zone sand production may stick tubing.  Work-over of upper zone requires killing lower zone.

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3. Cross-over dual completion –single tubing  Again, There is both tubing and annulus flow.  Advantage is that cross-over choke permits upper zone to be flowed through tubing.

Limitations  Casing subject to pressure and corrosion.

 Must kill both zones for work-over of upper zone  Any zones impossible can be artificially lifted.

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4. Dual completion-Parallel string-multiple packer Advantages  Can lift several zones simultaneously.  Concentric tubing and wire line workover practical in all zones.

Limitations  High cost.  Susceptibility to tubing and packer leaks.  Hesitation to perform stimulation treatments or workover of individual zones

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5. Parallel dual completion with two alternate completions Limitations Difficult of treating or even reperforating individual zones unless well is killed and tubing is pulled.

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6. Triple completion In this completion design three production tubing used with production packers. In this type could produce with high production rates in one well

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Unconventional tabular configuration  This completion called permanent well completion (PWC).  Involves cementing several strings of pipe inside one well-bore.  Originally this concept was applied to strings have outside diameter less or equal 4 ½ inch.

 The concept should not be thought of as being limited entirely to low volume producing or injection wells.

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Advantages  Reduced cost-initial completion and future work-over costs are reduced

 Each zone is independent and can be worked on without disturbing the other completions.  Communication between strings is easily located and eliminated.

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Limitations  Restricted production rate.  Corrosion and paraffin control more critical.  Higher risk due to pressured well fluids.

 High rate stimulation treatments are more difficult.  Long-zone sand control more difficult.

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Conceptual Design Principal decision areas are:

Bottom hole completion technique

 Selection of Production Conduit  Completion String Facilities (Next lecture)

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