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Introduction to Oilfield, Primary & Remedial Cementing
Agenda Introduction to the oil field Type of drilling rigs, rig equipment Oilwell Cementing
Step of Primary Cementation
Objectives of Primary Cementation
Execution of a Cement Job
Remedial Cementing
Cementing Equipment
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Types of Drilling Rig Basically two types of drilling rig: Offshore-based drilling platform – Floating – Fixed
Land-based drilling platform
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Types of Drilling Rig (Offshore) • Mobile Jack-up type • Used in shallow water – up to 100m • Found all over the world
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• Rig has three legs for stability
Types of Drilling Rig (Offshore) • Platform type • Used in oil production • Can have steel or concrete legs • Can drill and produce oil concurrently
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• Permanently fixed to sea floor
Types of Drilling Rig (Offshore) • Mobile semi-submersible type • Held in position with tensioned chains and anchors • Can be self-propelling • Widely used worldwide
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• Float on pontoons
Drilling Rig Equipment
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BOPs
Derrick
Casing
Mud System
Steps to Cementation 1. Drill the hole for each string of casing 2. Run casing as per hole size 4. Perform cement job(s): •
Conductor (~ 30 ft deep)
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Surface Casing (~ 800ft deep)
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Intermediate Casing (~ 3000 ft deep)
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Production Casing (~ 9000 ft deep)
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Liner (~ 10000 to 20000 ft deep)
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3. Circulate and condition drilling fluid (mud)
Objectives of Cement Job There are three main objectives: Provide complete isolation of zones
Support the casing / Wellbore stability
Protect casing string
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Executing a cement job
Casin g
Drilling Fluid
Flow inside the Casin g Spacer
Open Hole
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Cement is pumped down inside the casing. Cement then passes in the gap (or annulus) between the casing and open hole. It is displaced into position with drilling fluid. Spacers are often pumped ahead and behind to clean the hole and protect the cement.
Cement Slurry
Executing a cement job Cement mixed by two methods ‘on-the-fly’ or ‘batch’ mixed Pumped from the cement unit to the drill floor. Cement passes through a cement head Top Plug containing wiper plugs. Two types of plug – bottom and top – for specific reasons
Casing
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Bottom Plug
Cement
Primary Cementing Animations Single Stage Job Liner job Stab-in job Double stage job
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Remedial Cementing : Cement Plug
To side track (fish or DD)
To plug back a zone
To plug back a well (P&A))
To solve a lost-circulation
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A relatively small volume of cement slurry placed in the wellbore Common Purposes:
Squeeze Cementing packer
tubing FORMATION casing DEHYDRATED CEMENT
cement slurry
cement nodes
PRIMARY CEMENT
CHANNEL BEHIND CASING
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Primary cement job repair Unwanted Water Production High Gas-Oil Ratio (GOR) Casing Splits or Leaks Nonproductive or Depleted Zones
Effect of Fluid Loss Control Node build-up after 45 min, slurries with different fluid-loss, dP=1000psi 800 ml/30min
150 ml/30min
Partially bridged casing
50 ml/30min
Completely filled perforations
15 ml/30min
Partially filled perforations
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Completely bridged casing
Squeeze Cementing - Methods Pumping technique – Hesitation – Running – High pressure - above formation frac pressure – Low pressure - below formation frac pressure
Tools – Packer/Retainer – Bradenhead
Coiled tubing
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Placement technique
Running Squeeze
Pressure ( psi )
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Time (min) •
Time (min..)
Usually a large volume of slurry is pumped with this technique
Hesitation Squeeze
Pressure (psi)
A
10-20 min. intervals B
C
D
A
Time (min)
D
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Pressure (psi)
Rate of 0.25 - 0.5 bpm
Cement Units Onshore (1) The cement units are truck-mounted and mobile. Performs cementing operations
Performs other pumping jobs
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Cement Units Onshore (2) Trucks come in a variety of forms to cater for different landbased environments. Schlumberger Private
Cement Units Offshore (1) The cement unit is permanently fixed on each rig. Performs cementing operations
Performs other pumping jobs
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Cement Units Offshore (2) Each cement unit consists of: 2 x pump units
2 x engines
Mixing system
Liquid Additive system
Back up systems
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Questions?
Drilling Rig Equipment - Derrick The main structure through which all the drilling operations are performed.
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It can suspend many millions of pounds in weight, and is used to apply weight to the drill string.
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All drilling rigs will have a derrick of some form or another
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Drilling Rig Equipment – Mud System
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Drilling Rig Equipment - BOPs Subsea Blow-out Preventor (BOP) stacks are specially designed to operate under water at great depths.
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They are located on the sea bed, rather than above water on the rig.
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Subsea BOPs are used only on floating rigs.
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They are a very important safety device to prevent the well ‘blowing’ oil
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Casing Function •
from each other and the surface.
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A series of casing strings is necessary to complete a well and produce the desired fluid successfully. Casing is large pipe run into the wellbore to protect the integrity of the hole and to isolate various parts of the formation
Cement Head • • •
Used to hold the top and bottom plugs. Fixed to top of casing during cement job. Pumping sequence:
Pump spacer ahead Drop bottom plug Pump cement slurry Drop top plug Displace cement with drilling fluid
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Cement Head – Operation
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Cement Unit Schematic
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