Handy Hermanjaya Setiawan (113120009)Syaiful Aziz Nuruddin
(113120068)Aulia Novi Andini (113120069)Prasidya Kharisma Ibrahim
(113120076)
The casing design process involves three distinct operations:
The selection of the casing sizes and setting depths; The
definition of the operational scenarios which will result in burst,
collapse and axial loadsThe calculation of the magnitude of these
loads and selection of an appropriate weight and grade of
casing.Casing DesignIntroduction
Casing DesignCalculate Loads on the Casing Axial Load The axial
load on the casing can be either tensile or compressive, depending
on the operating conditions.
Casing DesignCalculate Loads on the Casing Burst PressureThe
casing will experience a net burst loading if the internal radial
load exceedsthe external radial load.
The casing will experience a net collapse loading if the
external radial load exceeds the internal radial load. The greatest
collapse load on the casing will occur if the casing is evacuated
(empty) for any reason.Casing DesignCalculate Loads on the Casing
Collapse Pressure
If external pressure exceeds internal pressure, the casing is
subjected to collapse. Such conditions may exist during cementing
operations or well evacuation. Collapse strength is primarily
function of the materials yield strength and its slenderness ratio,
dn/t. Casing DesignCalculate Loads on the Casing Collapse
Pressure
Plastic collapse: Plastic collapse is based on empirical data
from 2,488 tests of K-55, N-80 and P-110 seamless casing. No
analytic expression has been derived that accurately models
collapse behavior in this regime. The minimum collapse pressure for
the plastic range of collapse is calculated by equation (10).Casing
DesignCollapse Pressure Regimes
Transition Collapse: Transition collapse is obtained by a
numerical curve fitting between the plastic and elastic regimes.
The minimum collapse pressure for the plastic-to-elastic transition
zone is calculated by equation (11)Casing DesignCollapse Pressure
Regimes
Elastic Collapse: Elastic collapse is based on theoretical
elastic instability failure; this criterion is independent of yield
strength and applicable to thin-wall pipe (dn/t > 25). The
minimum collapse pressure for the elastic range of collapse is
calculated by using equation (12)
Most oilfield tubulars experience collapse in the plastic and
transition regimes.
Casing DesignCollapse Pressure Regimes
Casing DesignCombined Stress Effects
As axial tension increases, the critical burst-pressure
increases and the critical collapse-pressure decreases.In contrast,
as the axial compression increases, the critical burst-pressure
decreases and the critical collapse-pressure increases.Casing
DesignCombined Stress Effects
