Sunday, 9 October 2016
Enhanced oil recovery
Enhanced oil recovery (abbreviated EOR) is the implementation of various techniques for increasing the amount of crude oil that can be extracted from an oil field. Enhanced oil recovery is also called improved oil recovery or tertiary recovery (as opposed to primary and secondary recovery).
Friday, 19 February 2016
Downhole Motors - Turbines- Turbine Characteristics
Turbine Characteristics
• Torque and RPM are inversely proportional (i.e. as RPM increases,
torque decreases and vice versa).
• RPM is directly proportional to flow rate (at a constant torque).
• Torque is a function of flow rate, mud density, blade angle and the
number of stages, and varies if weight-on-bit varies.
• Optimum power output takes place when thrust bearings are balanced.
• Changing the flow rate causes the characteristic curve to shift.
• Off bottom, the turbine RPM will reach “run away speed” and torque
is zero.
• On bottom, and just at stall, the turbine achieves maximum torque and
RPM is zero.
• Optimum performance is at half the stall torque and at half the
runaway speed, the turbine then achieves maximum horsepower.
• A stabilized turbine used in tangent sections will normally cause the
hole to “walk” to the left.
• Torque and RPM are inversely proportional (i.e. as RPM increases,
torque decreases and vice versa).
• RPM is directly proportional to flow rate (at a constant torque).
• Torque is a function of flow rate, mud density, blade angle and the
number of stages, and varies if weight-on-bit varies.
• Optimum power output takes place when thrust bearings are balanced.
• Changing the flow rate causes the characteristic curve to shift.
• Off bottom, the turbine RPM will reach “run away speed” and torque
is zero.
• On bottom, and just at stall, the turbine achieves maximum torque and
RPM is zero.
• Optimum performance is at half the stall torque and at half the
runaway speed, the turbine then achieves maximum horsepower.
• A stabilized turbine used in tangent sections will normally cause the
hole to “walk” to the left.
Downhole Motors - Turbines- Turbine Observations
Turbine Observations
• There is minimal surface indication of a turbine stalling.
• Turbines do not readily allow the pumping of LCM.
• Sand content of the drilling fluid should be kept to a minimum.
• Due to minimal rubber components, the turbine is able to operate in
high temperature wells.
• Pressure drop through the tool is typically high and can be anything
from 500 psi to over 2000 psi.
• Turbines do not require a by-pass valve.
• Usually, the maximum allowable bearing wear is of the order of 4mm.
• There is minimal surface indication of a turbine stalling.
• Turbines do not readily allow the pumping of LCM.
• Sand content of the drilling fluid should be kept to a minimum.
• Due to minimal rubber components, the turbine is able to operate in
high temperature wells.
• Pressure drop through the tool is typically high and can be anything
from 500 psi to over 2000 psi.
• Turbines do not require a by-pass valve.
• Usually, the maximum allowable bearing wear is of the order of 4mm.
Downhole Motors - Turbines- Directional Turbine
Directional Turbine
This is a short tool which has a set number of stages and its bearing section
entirely within one housing. That is, it is not a sectional tool and will be
typically less than 30 feet long. It is designed for short runs to kick off or
correct a directional well, using a bent sub as the deflection device.
Steerable turbodrills do exist and will be discussed later.
This is a short tool which has a set number of stages and its bearing section
entirely within one housing. That is, it is not a sectional tool and will be
typically less than 30 feet long. It is designed for short runs to kick off or
correct a directional well, using a bent sub as the deflection device.
Steerable turbodrills do exist and will be discussed later.
Downhole Motors - Turbines- Bearing Section
Bearing Section
Usually, thrust bearings are made up of rubber discs (Figure 5-24) which
are non-rotating (being fixed to the outer housing of the tool) and rotating
steel discs attached to the central rotating shaft. Long bearing sections
known as cartridges are used for long life in tangent or straight hole drilling
sections. These are changeable at the rigsite. If the bearings wear past the
maximum point, considerable damage can be inflicted as the steel rotors
will crash into the stators below.
Usually, thrust bearings are made up of rubber discs (Figure 5-24) which
are non-rotating (being fixed to the outer housing of the tool) and rotating
steel discs attached to the central rotating shaft. Long bearing sections
known as cartridges are used for long life in tangent or straight hole drilling
sections. These are changeable at the rigsite. If the bearings wear past the
maximum point, considerable damage can be inflicted as the steel rotors
will crash into the stators below.
Downhole Motors - Turbines- Drive Section
Drive Section
This will consist of a series of bladed stators, fixed to the outer tool housing
and bladed rotors fixed to the central rotating shaft. Mud flow is deflected
at a pre-determined angle off the stator blades to hit the rotor blades and
cause the shaft to rotate. The angle of the blades will affect the torque and
speed output of the turbine
This will consist of a series of bladed stators, fixed to the outer tool housing
and bladed rotors fixed to the central rotating shaft. Mud flow is deflected
at a pre-determined angle off the stator blades to hit the rotor blades and
cause the shaft to rotate. The angle of the blades will affect the torque and
speed output of the turbine
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