Тандем - 2, шлакоблочные станки, бетоносмесители


Производство оборудования и технологии
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SUSPENDING THE WELL

When the well is cleaned up the master valves on the tree are closed and the riser system is displaced to seawater. The riser is then disconnected from the top of the tree and the riser retrieved. A tree cap is then run and latched onto the top of the tree. The well is now ready for connection of the pipelines and control umbilical and production.

2. abandonment

If the well is dry and is to be abandoned several cement plugs will be set in the open hole section and a various positions in the casing and the casing will be cut and retrieved as deep as possible. In the North Sea, Health and Safety Executive Regulations require that all strings of casing are cut 10ft. or more below the seabed, and that all structures above this point should be recovered. Also any debris lying on the seabed, within a 70m radius of the drilling location should be removed. Hydraulically operated casing cutting tools can be used to cut through the casing strings from the inside. However, this method is time consuming and will probably cost more than the value of the recovered wellhead. For this reason explosive charges are sometimes used to sever the wellhead below the seabed when the rig has moved off location. This work is usually done by salvage contractors.

• SURFACE TO BIT TRAVEL TIME

• If several different designs are possible, choose the most economical scheme that meets requirements.

• Centralisers — these are hinged metal ribs which are installed on the casing string as it is run (Figure 7). Their function is to keep the casing away from the borehole so that there is some annular clearance around the entire circumference of the casing

The proper use of centralisers will help to:

• Improve displacement efficiency (i. e. place cement all the way around the casing)

• Prevent differential sticking

• Keep casing out of keyseats

• Wipers/scratchers — these are devices run on the outside of the casing to remove mud cake and break up gelled mud. They are sometimes used through the production zone.

• Long pumping times

• High pump pressures

• Excessive hydrostatic pressure on weak formations due to the relatively high density of cement slurries.

• To prevent fluids escaping from abandoned zones.

• A negative pressure test (or inflow test) can be performed by reducing the hydrostatic pressure inside the casing. This can be done using a DST tool or displacing with the well to diesel. This test is more meaningful since mud filled perforations may hold pressure from the casing, but may become unblocked when pressure from the formation is applied.

• Select a section of clean hole which is in gauge, and calculate the volume required (add on a certain amount of excess). The plug should be long enough to allow for some contamination (500′ plugs are common). The top of the plug should be 250′ above the productive zone

• Condition the mud prior to placing the plug

• Use a preflush fluid ahead of the cement

• Use densified cement slurry (ie less mixwater than normal)

5. DOWNHOLE TELEMETRY TOOLS

6. INERTIAL NAviGATION SYSTEMS

7. STEERING TOOLS

[1] The formation pore pressure

• The mudweight required to kill the well

• The type of influx

[2] The One Circulation Method

• The Drillers Method

[3] Blind rams — which completely close off the wellbore when there is no pipe in the hole.

• Pipe rams — which seal off around a specific size of pipe thus sealing of the annulus. In 1980 variable rams were made available by manufacturers. These rams will close and seal on a range of drillpipe sizes.

• Shear rams which are the same as blind rams except that they can cut through drillpipe for emergency shut-in but should only be used as a last resort. A set of pipe rams may be installed below the shear rams to support the severed drillstring.

[4] Temperature effects — high temperatures will tend to expand the pipe, causing buckling. This must be considered in geothermal wells.

[5] The cement slurry does not set whilst it is being pumped

• The cement slurry is not sitting in position as a slurry for long periods, potentially being contaminated by the formation fluids or other contaminants

[6] photographic surveying TOOLS

4.1 Magnetic Single Shot

4.2 Magnetic Multi-shot

4.3 Gyro Single Shot

4.4 GyroMulti-Shot

4.5 Accuracy of Photographic Survey Results

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