Chapter 8 Well Completions

• Preparing

a well for production

• Christmas trees • Functions of a completion • Primary recovery • Secondary recovery • Tertiary recovery • Production systems and equipment • Well servicing and maintenance

How is a Well is Completed?

•

Different types of completions:

• • • • • •

Open hole Cased hole Single string Dual string Gravel packed

Completing the well:

• • •

Hang tubing from the wellhead Seal the top of the casing with a tubing hanger Seal the foot of the well with a packer

Examples of Completion Packer Functions Dual Packer Short String

Casing

Long String

Casing Annulus Production Tubing

Dual Zone/Dual String Completion Packer #1

Packer Packer #2 Packer #3

Single Zone/Single String Completion

Multi Zone/Single String Completion

Preparing A Well For Production

Step 2: Run the Tubing

Step 3: Perforate the Casing

Step 4: Install Christmas tree

Christmas Tree

Composite Design

•

Cost effective

•

Alternative stack-up arrangements possible

•

Repair by replacement as needed

Completion Functions

• The Starting Point

Completion Functions

• Optimise Flow

Completion Functions

• Protect the Casing

Completion Functions

• Contain the Reservoir

Completion Functions

• Allow Well Kill

Completion Functions

• Install the Tubing String

Completion Functions

• Limit Production Problems

Primary Recovery

• Uses the natural energy drive of well systems to produce

• Primary recovery often only taps 10% of available reserves.

Depletion

Gaseous oil mix

Gas cap

Combined drainage

Gravity drainage

• The average oil well actually

produces 7 barrels of water for every barrel of oil brought to the surface.

• Treating and disposing of this water

is a major challenge and is very costly

Secondary Recovery

•Secondary recovery is mechanical it can

bring another 20% of the oil to the surface

Depletion 20,000 bbl/day Darcy’s Law Undamaged Well

Formation damage – “ a reduction of permeability around a wellbore, which is the consequence of drilling, completion, injection, attempted stimulation, or production of that well.” Formation damage due to physical reduction in pore/pore throat size a.

Drilling mud solids invasion

b.

Drilling mud filtrate invasion

c.

Cement filtrate invasion

d.

Completion/workover solids invasion

e.

Perforation damaged zone

f.

Plugging of pores w/native clays

8 ½” Hole

w/ 100 mD Permeability

50 ft

1

Reservoir Pressure 7000 psi

7000

100

1000

10

1300 psi

6000 5000 Bottomhole flowing Pressure 2500 psi

4000 3000

1300 psi 1300 psi 600 psi drop in 8 inches

2000 Notice the pressure drop in the last 8 inches around the wellbore. You can imagine how badly the well productivity would suffer if this area had formation damage.

Nodding donkey

Tertiary Recovery

Tertiary recovery is used to recovering any remaining oil.

• • •

Thermal recovery Gas Injection Chemical flooding

Artificial lift

Gas lift

Gravel packing

Separation

Oil and water

Separation

Water gas and oil

Well Servicing/ Maintenance Well Servicing /Maintenance

Routine Monitoring

Well Testing

Wireline

Production Facility

Wellhead Servicing

Pumping

Live Well Interventions

C/T or Snubbing

Service Units

Dead Well Workovers

Repairs

ReComplete

Drilling or Workover Rig

Emergency Situations

Capping

Well Kill

Production Facility /Snubbing Unit

Well Servicing Methods

Coiled Tubing

Snubbing

Drilling Unit

Coiled Tubing Operations The coil tubing unit uses a continuous length of small diameter tubing that is stored on a reel. Coil tubing units uses include:

• • • • •

Sand washing Jetting Spot acidizing, Mud washing Cementing, etc.

Basic Coiled Tubing Rig Up INJECTOR HEAD

STRIPPER BLIND SHEAR SLIP PIPE

RISER SHEAR SEAL BOP

CONTROL CAB

REEL

XMASS TREE

Slickline Rig Up

Grease Injection Rig Up

Typical Toolstring The diameters in most common use are 1 1/2" and 1 7/8", but toolstring components are also available in 1", 1 1/4", 2 1/8" and 2 1/2" diameters. Rope Socket

Provides a connection with wire.

Swivel Joint

Attached between the rope socket and stem if required.

Stem

To add weight / mass to the toolstring to overcome well pressure and friction, and provide impact downhole.

Upstroke Jars

Attached here if required.

Mechanical Jars

To provide a means of generating impact.

Knuckle Joint *

Attached here if required

*Attach the required tool to the bottom of the jars or knuckle Joint

Snubbing Used in preference to coiled tubing when:

• •

Need greater depth

•

Greater diameter (3.5 inch OD or over) are required (e.g. for circulation capacities)

•

Rotating capacity required (under

Well pressures at surface (to snub against) or well pressures downhole (risk of collapse) are too high for a Coiled Tubing workstring

well pressure)

•

Higher strength/operating capabilities are required to accomplish as specific task