FE 02-10 Casing and Cementing

Nội dung text: FE 02-10 Casing and Cementing

1. Casing • Casing is strong steel pipe used to ensure a pressure-tight connection from the surface to the casing depth • Ranges from 16 ft (5 m) to > 42 ft (13 m) in length and 4.5 to 36 in (11.5 – 91.5 mm) in diameter
2. Casing Types • Conductor casing • Surface casing • Production casing • Intermediate casing • Liner
3. Conductor Casing or Pipe: Uses • As a channel to raise the mud high enough to return to the mud pits • To prevent erosion around the base of the rig • To provide for attaching the BOP stack where shallow gas is expected • To protect the subsequent casing strings from corrosion • To support some of the wellhead load on locations where the ground is soft
4. Surface Casing: Uses • Primarily for protection in case of a blowout, so this string is usually designed to withstand a burst pressure equivalent to 1 psi/ft of depth • Set deep enough to protect the well from cave-in and washout of loose formations that are encountered near the surface • Starting point for the casing head and other fittings that will be left on the completed well
5. Production Casing or Liner: Uses • Isolate the producing reservoir from undesirable fluids • Protective housing for the completion tubing and other equipment to be used in producing the well
6. Intermediate Casing: Uses • Generally used to seal off weak zones that might break with the use of heavy mud and withstand pressure at the wellhead when kicks are being handled • Sometimes used to seal off salt and anhydrite zones that may contaminate the drilling mud or cause pipe sticking and key seats • Also used to seal off older production zones in order to drill deeper
7. Liner: Advantages • Cheaper because only a short string of pipe is needed instead of a complete string back to the surface (principal advantage) • Cheaper means of testing a lower zone • Less danger of the casing being stuck because a liner can be run in a shorter amount of time • If drilling has weakened the casing string, additional pipe may be tied back to the surface from the top of the liner
8. Casing Accessories • Guide shoe • Float collar • Centralizer • Cement scratcher • Multistage cementing devices
9. Float Shoe • Similar to a guide shoe except that it has a check valve that prevents U-tubing of the cement from the annulus to the casing • Serves the function of both the guide shoe and the float collar
10. Centralizers • To ensure a reasonably uniform distribution of cement around the pipe (by having a “centered’ casing) • To obtain a complete seal between the casing and the formation • May help to remove wall cake and to prevent cement channeling in the annulus
11. Multistage Cementing Devices • Used for cementing two or more separate sections behind a casing string, usually for a long column that might cause formation breakdown if the cement were displaced from the bottom of the string • The tool consists of a ported coupling placed at the proper point in the string • Special plugs open it up hydraulically
12. Running Casing • Each casing joint is lifted by casing elevators on the traveling block and guided (stabbed) into the casing string already being suspended in the well
13. Running Casing • The casing string is finally landed by transferring the weight of the string to the casing hangers in the casinghead on the top of the well.
14. Portland Cement • Main ingredient of all drilling cements • An artificial cement invented by Joseph Aspdin made by burning a blend of limestone and clay
15. Cement: Functions • Support and protect the casing • Prevent the movement of fluid through the annular space outside the casing • Stop the movement of fluid into vugular or fractured formations • Close an abandoned well or a portion of a well • Sidetracking
16. Cementing Head • Made up on the top joint of casing that is hanging in the elevator • Also called plug container • Function: – Provides a connection from the cementing pumps so that cement may be circulated – Bottom wiper plug and a top wiper plug are placed there
17. Cement Wiper Plugs • Bottom wiper plug – rubber plug with a thin rupture diaphragm; wipes the mud from the casing ahead of the slurry to minimize the cement contamination by mud • Top plug – solid rubber plug
18. Types of Cementing • Primary Cementing • Squeeze Cementing – Shoe – Casing (up-hole) – Open-hole (lost-circulation) • Plugging – Open-hole plug back • Fishing Operations • Abandonment – After Casing Cut
19. Pumping Cement (Single Stage) 1. Pressure test surface lines. 2. Pump a spacer or mud preflush of about 10 to 50 barrels of water before pumping the cement slurry 3. Drop bottom plug and pump cement slurry 4. Bottom plug stops at the float collar 5. Pump pressure increases and ruptures the diaphragm in the plug and the slurry goes through and out in the annulus
20. Positions of Wiper Plugs
21. Stage Cementing: Procedure • Cementing of the lower section of casing is done first in the usual manner, using plugs that will pass through the stage collar without opening the ports • Special plugs then open the multistage tool hydraulically • Placement of cement for the upper section occurs through the ports, which are subsequently closed by the final plug pumped behind the cement
22. Squeeze Cementing: Purpose • To form a hydraulic seal between the hole and the squeezed zone
23. Squeeze Cementing
24. Plug Cementing
25. Pressure Testing the Casing and Cement • Casing and cementing jobs are always pressure-tested before drilling ahead • In most areas casing is pressure-tested after the casinghead and blowout preventers have been installed
26. End of Topic