Plan de Calidad del Sistema Nacional de Salud

4.0 – Introduction to drilling a well

The following graphics show the major sequence of operations involved in drilling a well from a Mobile Offshore Drilling Unit (MODU) starting from the initial drilling phase, also called “spud in”, through running the production tubing.

The diagram above shows the typical arrangement for a 30/36” (Conductor Pipe) x 20” (Surface Casing) x 13-3/8” (Intermediate) x 9-5/8”/10-3/4” (Production Casing).

This graphic depicts the location of the reservoir below the sea floor. This reservoir could be located anywhere from 1000 ft to 10,000 ft below the sea floor and in some cases even more than this. The reservoir is the target for the drilling operations.

WARNING: This information is provided to FMC customers solely to illustrate the operation of FMC equipment. It does not provide complete information for

After the rig is on location and anchored in position if the rig is not dynamically positioned and prior to the start of the surface hole drilling operations some operators run a Temporary Guide Base (TGB) to land on the sea floor. Guide lines are attached to the TGB that extend back to the rig. These wires guide the drilling tool string and surface conductor pipe into the well. This type of equipment would be used in water depths typically up to 2000 feet. Beyond 2000 feet, guide lines become impractical due to their weight.

The first operation to take place is to drill the surface hole section. This is commonly referred to as “spudding the well.”

A drill bit is run with a bottom hole assembly consisting of heavy sections of pipe called drill collars and lowered to the sea floor on drill pipe. Sea water is then pumped through the drill bit as it is rotated to drill the hole.

It is always preferred that the surface hole section is drilled and the surface casing installed rather than “jetting” the surface casing into position as this improves the possibility of the surface casing being in a true vertical position inside the drilled hole.

After the 36” surface hole section is drilled, typically to a depth of +/- 100-150 meters, the 30/36” conductor pipe is run. The FMC 30/36” conductor housing is welded to the top of the surface casing string. If guide line will be used on the well, a Permanent Guide Base (PGB) will be attached to the outside of the conductor housing.

This assembly will be lowered on drill pipe connected to a running tool that is made up to the 30” conductor housing. When a TGB is used, the PGB will land on the TGB.

WARNING: This information is provided to FMC customers solely to illustrate the operation of FMC equipment. It does not provide complete information for

The 30/36” conductor pipe is then cemented in place by pumping cement through the drill pipe landing string, out the bottom of the casing, and into the hole section. The casing would be held in suspension by the drill pipe landing string until the cement hardens sufficiently to support the weight of the casing.

Note that the hole drilled for the casing will not be a straight 36” hole section. Soft formations may be washed out as the hole is being drilled resulting in a hole of various sizes and in some cases there may be large cavities where the formation has been washed away.

For this reason the cement volume pumped may be in 100 to 200% excess above the normal required to fill the drilled hole. This is to ensure a strong foundation is provided for subsequent subsea equipment to land and be supported.

An alternative method of installing the 30/36” surface casing is to “jet” the casing into position. Soft bottom conditions are required to allow this method to be used. The jetting operation involves pumping sea water through drill pipe that is attached to the bottom of the 30” wellhead running tool. The drill pipe is spaced out to locate the drill bit just inside the bottom the 30/36 casing.

As the casing is lowered, the pump pressure washes away the formation and the

casing sinks by virtue of its own weight to the desired depth. When jetting operations are complete, the conductor housing is typically 3-4 meters above the sea floor. After pumping is stopped, the formation will settle in place around the casing and the skin friction of the sediment will support the weight of the casing. No cement is required.

This method is typically used in the Gulf of Mexico. Care must be taken that the casing is installed in a true vertical position. FMC does not recommend that the casing be more than 2 degrees from vertical as any angle above this would cause problems in subsequent drilling, completion, and tie back operations.

WARNING: This information is provided to FMC customers solely to illustrate the operation of FMC equipment. It does not provide complete information for

After the 30/36” casing is installed, the 30” wellhead running tool would be released and retrieved. A 26” drill bit would then be run to drill the hole for the next casing that is typically 20” O.D.

The hole would be drilled to the desired casing depth, which is typically 500 to 600 meters. Fluid returns from the drilled hole would be pumped to the top of the 30/36”

conductor pipe and exit through side exit ports in the side of the wellhead housing.

The 20” surface casing would then be run with the high pressure wellhead housing welded to the top of the casing string. The assembly would be lowered on drill pipe connected to a wellhead running tool made up to the high pressure wellhead housing.

The high pressure wellhead would then be lowered to land out and lock into the 30”

conductor housing.

WARNING: This information is provided to FMC customers solely to illustrate the operation of FMC equipment. It does not provide complete information for

The 20” surface casing would then be cemented in place by pumping cement through the drill pipe landing string, out the bottom of the 20” casing and into the 30” x 20”

casing annulus.

Fluid returns would exit the 30” casing via the side exit holes in the side of the 30”

conductor housing.

After the cementing operations were complete the wellhead running tool would be released and retrieved to surface.

The subsea Blow Out Preventor (BOP) would then run and landed on the high pressure wellhead housing. Using the BOP control system the BOP hydraulic wellhead

connector would be locked to the wellhead housing.

A test tool would then be run and landed in the wellhead housing to allow pressure testing of the BOP-to-wellhead connection

The next section of hole would then be drilled. This hole will typically accommodate 13-3/8” intermediate casing.

WARNING: This information is provided to FMC customers solely to illustrate the operation of FMC equipment. It does not provide complete information for

The 13-3/8” intermediate casing string would then run and landed inside the wellhead housing. The casing would typically be lowered on drill pipe using a single trip tool that allows the casing and annulus seal assembly to be installed together.

At the top of the casing string would be the 13-3/8” casing hanger. This hanger would land on the high strength load shoulder in the bottom of the 18-3/4” wellhead housing.

The casing would then be cemented in place by pumping cement through the drill pipe landing, out the bottom of the casing and into the 20” x 13-3/8” annulus. Fluid returns from the well would be circulated back to the rig. The annulus seal assembly would then be set and tested.

The hole section for the production casing, which is typically 9-5/8” or 10-3/4”, would then be drilled. The casing would be installed, cemented, and the annulus seal

assembly would be set per the same procedures as the intermediate casing string A hole section into the reservoir would then be drilled. The production tubing would then be installed through the completions equipment and production of hydrocarbons could begin.

Section 5