TEKNIK PENULISAN 1 - fcee.utm.myfcee.utm.my/issham/files/2012/09/Chapter-1Casing.pdf · CASING....
Transcript of TEKNIK PENULISAN 1 - fcee.utm.myfcee.utm.my/issham/files/2012/09/Chapter-1Casing.pdf · CASING....
Assoc. Prof. Issham Ismail
Faculty of Chemical & Energy Engineering,
Universiti Teknologi Malaysia,
Johor Bahru, Malaysia.
These presentation slides are strictly for domestic use.
CASING
WHAT IS CASING?
The first stage after the completion of
drilling phase is equipping the well with
casing!
DIFFERENCE BETWEEN
A CASING JOINT & TUBING JOINT
Steel pipe placed in an oil or gas well as
drilling progresses to prevent the wall of
the hole from caving in during drilling, to
prevent seepage of fluids, and to provide a
means of extracting petroleum if the well
is productive.
Casing(Definition)
To keep the hole open and to provide a support for weak or fractured formations.
To isolate porous media with different fluid/pressure regimes from contaminating the pay zone.
To prevent contamination of near-surface fresh water zone.
To provide a passage for hydrocarbon fluids.
To provide a suitable connection for BOP and well equipment.
To provide a hole of known diameter and depth.
Casing(Functions)
Drive pipe/stove pipe
Conductor casing
Surface casing (BOPs are connected to the top of it)
Intermediate casing
Production casing
Liner casing
Types of Casing
Marine conductor or foundation pile for offshore drilling.
To prevent washout of near-surface unconsolidated formations.
To provide a circulation system for the drilling mud.
To ensure stability of the ground surface upon which the rig is sited.
Does not carry wellhead equipment.
Driven into the ground with a pile driver.
Size ranging from 26 in to 42 in.
Stove Pipe
Installed from surface to some shallow depth to protect near-surface unconsolidated formations, and provide a circuit for the drilling mud.
Installed a diverter system or may be a BOP.
Cemented to the surface and used to support subsequent casing strings and wellhead equipment.
Sizes used: 18 5/8 in, 20 in, and 30 in
Conductor Pipe
Set in competent rocks to prevent caving of weak formations, protect against troublesome formations, water sand, etc.
BOPs are connected to the top of this string.
Cemented to the surface.
Sizes used: 18 5/8 in, 13 3/8 in, and 20 in.
Surface Casing
Set in the transition zone below or above an over-pressured
zone.
Used to seal off a severe-loss zone, or to protect against
salt sections or caving shales.
Cemented to the surface.
Sizes used: 9 5/8 in (depends on the tubing/production
casing size).
Intermediate Casing
Represents the last casing string.
Used to isolate producing zones, provide reservoir fluid
control, and to permit selective production in multizone
production.
The casing string thru which the well will be completed.
Cemented to 200 ft above the topmost HC zone.
Sizes used: 7 in (depends on the tubing/production casing
size).
Production Casing
Does not reach the surface – hung on the intermediate casing
using a suitable arrangement of a packer and slips called a
liner hanger.
Both liner and intermediate string act as the production string.
The advantages are reduce total costs and cementing time, and
the length of reduced diameter is reduced.
The disadvantages are possible leak across a liner and difficult
to get a primary cementation due to the narrow annulus
between the liner and the hole.
Liner Casing
Yield strength for pipe body and coupling – API defines as tensile
stress required to produce a total elongation of 0.5% of the gage length, as
determined by an extensometer.
Collapse strength – defined as the maximum external pressure required
to collapse a specimen of casing.
Burst strength for plain pipe and coupling – defined as the
maximum value of internal pressure required to cause the steel to yield.
Casing Strength Properties
Outside diameter and wall thickness – To cater for production requirements, and problems and pressures vary along any section of hole.
Weight per unit length – (1) Nominal Weight (identification during ordering), (2) Plain End Weight (without the inclusion of threads and couplings), (3) Threaded and Coupled Weight (average weight of a joint including the threads at both ends and a coupling at one end).
Type of coupling – (1) API 8 round thread, (2) Buttress thread, (3) Vam thread, (4) Extreme line threaded coupling, (5) Buttress double seal, etc. Please see next slide
Length of joint – Please see next slide.
Grade of steel – Please see next slide.
Casing Specification
Length of Joint
Range Length (ft) Average Length (ft)
1
2
3
16 – 25
25 – 34
Over 34
22
31
42
Grade of Steel
Grade Min Yield Strength (psi) Min Tensile Strength (psi)
H40
J55
K55
C-75
N-80
L-80
C-95
P110
40 000
55 000
55 000
75 000
80 000
80 000
95 000
110 000
60 000
70 000 – 95 000
70 000 – 95 000
95 000
100 000
100 000
105 000
125 000
1) If the maximum anticipated pressure is 17.2 ppg, next determine the total imposed pressure: 17.2 ppg (formation pressure – actual mud weight)
0.3 ppg (trip margin – actual mud weight)
0.3 ppg (surge pressure – equivalent mud weight)
0.2 ppg (safety margin – equivalent mud weight)Total 18.0 ppg
2) Determine those formation that cannot withstand a 18.0 ppg pressure.
3) The minimum depth found is 12,100 ft (refer to next 3 slides)
Setting Depth(Intermediate or deeper strings)
May use the following equation:
EMW = (Total depth/surface depth) (0.5) + Original mud weight
where
EMW = Equivalent mud weight at any depth, ppg
Total depth = Depth of deepest interval, ft
Surface depth = depth of interest, ft
(0.5) = Incremental mud weight increase, ppg
Original mud weight = Mud weight in use.
Setting Depth(Surface Casing)
Example:
An operator wishes to drill a well to 12,000 ft and use
sufficient surface casing so that an intermediate string is not
required. If the maximum anticipated mud weight at 12,000 ft
is 11.9 ppg, where must the surface casing be set? Use the
previously shown equation and the Eaton fracture gradient
chart.
Setting Depth(Surface Casing)
Eaton’s chart
Solution
1) Select a shallow depth and calculate the EMW and fracture gradient.
(a) EMW = (12,000 ft/1,800 ft) (0.5 ppg) + 11.9 ppg = 15.2 ppg
(b) From Eaton’s chart, the fracture gradient would be 12.7 ppg if
normal formation pressures are assumed.
2) Since the EMW exceeds the fracture gradient, a deeper interval must be evaluated. Sampel results are as follows:
Depth (ft) EMW (ppg) Fracture gradient (ppg)
1,800 15.2 12.7
2,400 14.4 13.3
2,700 14.1 13.5
3,000 13.9 13.7
3,300 13.7 13.8
3,500 13.6 14.0
3) A depth of 3,300 – 3,600 ft would be selected as the surface casing setting depth.
Setting Depth(Surface Casing)
Design criteria:
Tensile force (safety factor 1.6 – 1.8)
Collapse pressure (0.85 – 1.125)
Burst pressure (1.0 – 1.1)
Casing Design
Casing on rack
Oilwell Tubing
Casing with Protector
Lifting Casing
Lifting-up a Casing
Casing to be lifted
to the rig floor
Making-up a Casing at the Rig Floor
Hydraulic casing tong
is used to make-up the
casing
Installing Casing
Derrickman is
connecting the
elevator to the top of
casing…lowers into
the hole
Bit Scratcher and
centraliser…do you
know their functions?
Installing Casing
Casing Accessories
Centralizer
Scratcher
Cementing & Casing accessories
THANK YOU
QUIZ
Explain briefly the three design criteria that
must be considered in casing design.
Explain briefly three general functions of a
casing string.