7. Workover Operations

W e l l

c o m p l e t i o n

a n d

i n t e r v e n t i o n

Workover Operation Course

Eng. Elsayed Amer Petroleum Engineer

BSC Of petroleum & NG engineering

Phone : 01065860658

Senior Process & Production Engineer

Email: [email protected]

Now petroleum Eng. At SUCO & RWE DEA

https://www.facebook.com/elsayedameer

Worked for weatherford drilling international

Married with twins Mai & Nada.

Page 4

About Workover

Welcome Introductions “…any work performed after the initial completion that alters the well performance or mechanical structure”

Page 5

01

Introduction Workover All jobs performed in a completed well any time during its productive live to enhance well integrity and production rate.

Types of Operations • Measurements • Maintenances

• Workover

01

Workover Operation Workover: The process of performing major maintenance or remedial treatments

on an oil or gas well.

• Increase or restore hydrocarbon production • Decrease water production • Repair mechanical failures

6

Page 7

Introduction

Well Intervention

Workover

8

Workover Operations

01

Measurements

✓ May involve the status of equipment ✓ Quality of pay zones-borehole connections ✓ Status of reservoir and well equipments etc.

02

Maintenances

✓ Simple operations that can be done on a well during production operations

03 02

Workover

✓ Heavier operations that might require the well to be killed ✓ Sometimes carried out with the well under pressure

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01

Reasons for work over

Installing New Equipment

Page 10

01

Reasons for work over

Casing window cutting for side track

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01

Reasons for work over

Well Plugging and abandonment

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01

Measurement Operations At the Wellhead ➢ Pressure and temperatures, variation would mean modification in production conditions. ➢ Pressures or loss in pressures in the annulus to check integrity of packers, casing and production strings. ➢ In artificial lift operations to monitor stress on rods, pumps or gas lift valves. ➢ Safety valve testing etc. At the Tubing ➢ Calibrations and checks ➢ Corrosion or deposit problems etc. At the Bottom hole ➢ Checking top of sediments ➢ Production logs –density, flow rate or temperature.

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02

Maintenance Operations At the Wellhead ➢ Routine operations such as adjusting flow rates ➢ Opening and shutting in well. ➢ Replacing faulty parts downstream ➢ Periodic verification of safety valves etc. At the Tubing ➢ Operations connected with problems of deposits, corrosions etc. ➢ Injection of inhibitors, chemicals, de-emulsifiers, anti foaming agents etc. ➢ Operations for exchange of equipments downhole etc. At the Bottom hole ➢ Sand control, further perforations etc. ➢ Pumping chemicals etc.

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03

Workover Operations At the Wellhead ➢ Leaks in lower master valves, tubing hanger. ➢ Problems with SSSV control lines etc. ➢ Damaged back pressure valves and other wellhead components. At the Tubing ➢ Casing or tubing problems/leaks. ➢ Collapsed, burst or broken pipe. ➢ Tubing partially or totally plugged. At the Bottom hole ➢ Leaks in equipments that has seals such as packers, locators, slip joints etc. ➢ Gas lift valves, fish, broken rod, pumping problems ➢ Miscellaneous faulty downhole equipment such as sensors, control lines etc. Modification in production conditions Restoration pay zone –bore hole conditions Change well purpose Fishing

MINOR WORKOVERS

15

Workover operation techniques include

Wireline • • • • • • • • •

Tubing gage cutter Scale or paraffin removal Sand bailer Plugs installation SSSV repairs Gas Lift installation SSD shifting Perforation Through tubing activities

Pumping operations • • • • •

Well Killing Chemical Injection Acidizing Hydraulic fracturing pressure testing

Coil tube & Snubbing • • • • • • • • •

Chemical injection Acidizing Sand Clean out Cement plug Remedial through tubing gravel pack Fishing Scale clean out Non routing well kill Kick off

WORKOVER TECHNIQUES AND EQUIPMENT These will be discussed with reference to two different categories namely:(1) Internal through tubing operations (2) Tubing retrieval operations

(1) Internal Through Tubing Operations A number of techniques are available to access and intervene inside the production tubing including:• Conventional slick wireline operations • Through Flow Line techniques for application in subsea wells • Concentric tubing

(2) Tubing Retrieval Equipment

Equipment available to conduct such operations could be either:• A full drilling rig with the necessary BOP equipment and the capacity to pull tubing. • A concentric unit which can be installed over the producing well.

Data Required for

Successful Workover

DATA REQUIRED FOR WORKOVER

A

Fluid Levels In Tubing

B

Wellhead Pressure Rating

C

Formation Pressure

D

Casing & Tubing Sizes

E

Formation Fracture Pressure

F

Casing & Tubing Strengths

G

Infectivity Pressure

H

Maximum Allowable Surface Pressure (MASP)

19

PRODUCTION HISTORY 500

BOPD

400

300

BOPD

200

100

0 1991

1992

1993

1994

1995 Year

1996

1997

1998

20

500

1000

400

800

BOPD, BWPD

FTP 300

600

BOPD 200

400

100

200

BWPD 0 1991

0 1992

1993

1994

1995

Year

1996

1997

1998

Flowing pressure

WATER PRODUCTION HISTORY

Job preparation

Economic phases of field development

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23

SUCCESSFUL WORKOVER INVOLVE

unlimited

A

Step 1 - Diagnose the problem

B

Step 2 - Determine solutions

C

Step 3 - Prepare Workover procedures

D

Step 4 – Perform economic analysis

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A

Selecting Workover Rig Workover Rig wheel mounted, propelled unit containing a fabricated derrick and a pulling system that operates a multisheave traveling block with a "tubing line “drum.

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A

Selecting Workover Rig A number of factors will influence the selection of a Workover rig including:1. 2. 3.

The nature of the operation to be conducted. Tubing size. The suspended weight of the tubing string, pressure control requirements for well re-entry etc. 4. location of well, proximity to operating company base, space on rig/platform, crane lift capacity. 5. Economics - cost, availability and its impact on deferred production. 6. The reservoir characteristics for example:7. Type of fluid 8. Fluid contaminants e.g. H2 S content 9. Pressure, temperature, fluid rate etc. 10. Depth of well

01

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B

Killing the well Killing the well is the process of replacing the contents of production tubing with a fluid with sufficient density called kill fluid to overbalance the pressure in the producing formation

01

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B

Killing the well Pumping

Pumping is the simplest way to pump killing fluid through well bore

01

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B

Killing the well Circulating killing fluids

01

Reasons for Workover and remedial actions

COMMON REASONS FOR A WORKOVER

Formation Problems

• high water cut (water shut off) • Sand production (gravel pack ) • high gas oil ratio (gas shut off) • viscous oil (chemical treatment) • lower productivity (re - perf.+vacuum)

• formation damage (frac + acid)

COMMON REASONS FOR A WORKOVER

Some of the more common reasons for a workover are: • Repair mechanical damage • Stimulate an existing completion • Complete into a new reservoir

• Complete multiple reservoirs • Reduce/eliminate water/gas production • Reduce/eliminate water coning

• Repair faulty cement jobs

Potential Well Problems 1. Control of Water Production: • Excessive water production can lead to a number of production problems including ✓ loss of production and eventual well death ✓ expensive treatment and disposal costs, ✓ corrosion and scaling. • Recovery from water drive reservoirs • Significant increase in water production • Rise in water/oil contact as a result of reservoir depletion. ❑ Fingering • Water migrating along a high permeability streak. ❑ Water Conning • water is drawn up from the aquifer either across bedding planes leading to coning.

32

Potential Well Problems 1. Control of Water Production: • Water Drive in Oil Reservoirs Bottom-Water Drive

Oil producing well

Oil

Zone Water

Cross Section 33

Potential Well Problems 1. Control of Water Production: • Water Drive in Oil Reservoirs Edge-Water Drive

Oil producing well

Oil

Zone

Water

Water

Cross Section 34

Water Coning

Oil zone Cone Water

Water Breakthrough

Low permeability High permeability Intermediate permeability Low permeability

Water Communication

High pressure water sand Casing leak Water channel along bad cement job

Low pressure oil reservoir

38

Potential Well Problems 1. Control of Water Production:

Oil Rate

Water Rate

39

Solution Gas Drive in Oil Reservoirs

800

600

400

400

Pressure, psia

Oil production rate, STB/D

Typical Production Characteristics

300

200

200

100

0

0

Reservoir pressure Oil production rate

Time, years 40

Production data - lower oil production rate

2000 1900 1800 1700

Reservoir pressure

Oil production, MSTB/D

Water

20 15 10 5 0

Oil

Time, years 41

60 40 20 0

Water Cut, %

Pressure, psia

Water Drive in Oil Reservoirs Effect of Production Rate on Pressure

1300 1200 1100 1000 900

Oil production rate, MSTB/D

Pressure, psia

Gas Cap Drive Typical Production Characteristics

42

Production data Reservoir pressure

2 1

Oil

0

Time, years

Potential Well Problems 1. Control of Water Production: • Remedial Actions • Squeeze cementing • plugging back and re-completion • Straddle system

43

Potential Well Problems 1. Control of Water Production: • Remedial Actions • Straddle system

Perforation Shut Off

44

Potential Well Problems 1. Control of Water Production: • Remedial Actions • Squeeze cementing

45

Potential Well Problems 1. Control of Water Production: • Remedial Actions • plugging back and re-completion

46

Potential Well Problems 1. Control of Water Production: • Remedial Actions • P&A

47

Potential Well Problems 2. Low Reservoir Pressure • The reduction in reservoir pressure and hence flow rate is particularly acute in dissolved gas drive reservoirs. • In gas cap and water drive reservoirs, pressure maintenance techniques can often offset the reduction in pressure due to depletion.

48

Potential Well Problems 2. Low Reservoir Pressure • Remedial Actions • Recomplete the well with either smaller tubing or some form of artificial lift. • Injection

49

50

Potential Well Problems 2. Low Reservoir Pressure • Remedial Actions • Injection

51

Potential Well Problems 3. Poor permeability • Fields with low reservoir permeability suffer a rapid decline once the fluids near the wellbore are produced • Remedial Actions • Reservoir stimulation 1. Acidizing 2. Hydraulic frac

52

Potential Well Problems 3. Poor permeability • Remedial Actions • Matrix Acidizing usually accomplished

by

introducing a mild acid through the perfs

and

producing

into

an

reservoir

existing for

the

purpose of dissolving acid soluble solids and regaining or restoring production. This can be done by a coiled tubing unit, snubbing unit, or small tubing unit.

53

Potential Well Problems 3. Poor permeability • Remedial Actions • Matrix Acidizing usually accomplished

by

introducing a mild acid through the perfs

and

producing

into

an

reservoir

existing for

the

purpose of dissolving acid soluble solids and regaining or restoring production. This can be done by a coiled tubing unit, snubbing unit, or small tubing unit.

54

Potential Well Problems 3. Poor permeability • Remedial Actions • Hydraulic frac

55

Potential Well Problems 4. Wellbore Restrictions • Typical causes of restrictions include scale, sand, paraffin and asphalt etc. • Many of these problems may not be apparent during early field life but can become a significant problem as the field matures. • Remedial Actions • Mechanical remove of restriction. • Chemical remove of restriction.

57

Potential Well Problems 4. Wellbore Restrictions • Remedial Actions • Mechanical remove of restriction. 1. Scale and Sand milling out

58

Potential Well Problems 4. Wellbore Restrictions • Remedial Actions • Mechanical remove of restriction. 1. Scale and Sand under reaming

59

Potential Well Problems 4. Wellbore Restrictions • Remedial Actions • Chemical remove of restriction. 1. Jet Pump Sand Cleanout

60

Potential Well Problems 4. Wellbore Restrictions • Remedial Actions • Chemical remove of restriction. 2. Acid washing

61

Potential Well Problems 5. Mechanical failure • Mechanical failures of tubing, casing and downhole equipment often require a workover to rectify the problem. • Typical problems would include ✓ casing leaks, either as a result of corrosion or collapse, ✓ tubing failures, packer failures and ✓ Downhole safety valve failures. • Remedial Actions

• Replacement of downhole components by work over units • Expandable tubular

62

Potential Well Problems 5. Mechanical failure ✓ casing leaks, either as a result of corrosion or collapse,

63

Potential Well Problems 5. Mechanical failure ✓ casing leaks

64

Potential Well Problems 5. Mechanical failure ✓ tubing thread failures

Scab Liners

INFLATABLE PACKERS 65

Potential Well Problems 5. Mechanical failure ✓ tubing thread failures

Scab Liners 66

Potential Well Problems 5. Mechanical failure ✓ Downhole safety valve failures.

67

Potential Well Problems 6. Primary Cement Failures: ✓ A poor primary cement job which leaves channels behind the casing can lead to the influx of unwanted fluids and in certain instances casing collapse. • Remedial Actions • Squeeze cementing • Scab liners • Expandables

68

Potential Well Problems 6. Primary Cement Failures: • Remedial Actions

packer tubing FORMATION

• Squeeze cementing Forces cement slurry, under pressure, through perforations or holes in the casing or liner…..

casing cement slurry

cement nodes

DEHYDRATED CEMENT

PRIMARY CEMENT CHANNEL BEHIND CASING

69

Potential Well Problems 7. Sand Production: • Failure of reservoir formations and subsequent sand production from wellbore can cause ✓ Erosion of tubular and components ✓ Productivity impairment ✓ Clogging of separators

• Remedial Actions • Mechanical sand control ✓ Screens ✓ Gravel pack ✓ Frac pack ✓ Expandables • Sand Management✓ reservoir pressure maintenance 70

Potential Well Problems 7. Sand Production:

71

Potential Well Problems 7. Sand Production: INSIDE CASING GRAVEL PACK

UNDERREAMED CASING GRAVEL PACK

SCREEN LINER IN OPEN HOLE

OPEN HOLE GRAVEL PACK

UNDERREAMED OPEN HOLE GRAVEL PACK

72

Potential Well Problems 7. Sand Production:

73