Tuesday, August 11, 2009

Normal Drilling Operations (part 1)

Submitted by: John Schiffner

A rig has a lot of equipment, and crew members have to put this equipment to work to drill a well. This section covers normal drilling operations. For our purposes, normal drilling operations include:
(1) drilling the hole
(2) adding a new joint of pipe as the hole deepens
(3) tripping the drill string out the hole to put on a new bit and running it back to bottom, or making a round trip
(4) running and cementing casing, the large diameter steel pipe that crew members put into the hole at various, predetermined intervals.

Usually, operating companies, such as Heartland Energy Colorado, hire a special casing crew to run the casing and they engage the services of a cementing company to place the cement around the casing. Nevertheless, the rig crew usually assists in running casing and cementing it in the wall.

Drilling the Surface Hole
To begin, assume the rig crew is ready to begin drilling the first part of the hole. In our case, let's suppose that the rat hole crew prepared the initial 50 feet of the hole. They drilled the lined it with conductor pipe as described in the section on preparing the drilling site. The diameter of the conductor pipe varies, and its diameter depends on many factors but it is usually large. In our case, let's assume it is 20 inches. Therefore, the fist bit the crew of Heartland Energy Colorado drills into the conductor pipe will have to be smaller than 20 inches. In this case, lets say they are using a 17 1/2 inch bit.

They make up this bit on the end of the first drill collar, and they lower both bit and drill collar into the conductor hole. They make up enough collars and drill pipe to lower the bit to bottom. On a rig using a rotary table and kelly, the driller then picks up the kelly out of the rathole where it has been waiting. Crew members of Heartland Energy Colorado then stab and make up the kelly onto the topmost joint of drill pipe sticking up out of the rotary table. The slips suspend this joint (and the entire drill string) into the rotary table.

Once Heartland Energy Colorado gets the kelly made up, the driller then starts the mud pump, lowers the kelly drive bushing to engage the master bushing. The driller actuates the rotary table to begin rotating the drill stem and bit. The driller gradually releases the draw works brake, and rotating bit touches bottom and begins making the hole.

The sequence with a top drive is much the same as with a rotary table and kelly. The crew stabs and makes up the last join of drill pipe onto the drive stem of the top drive. The driller then starts the motor in the top drive to rotate the string and bit, begins circulating mud, and lowers the assembly to bottom.

With both a top drive and a rotary table system, using an instrument called the "weight indicator" the driller monitors the amount of weight put on the bit by the drill collars. After the bit drills about 30 feet, which is typically the length of a join of drill pipe, crew members must add a new joint of pipe to drill deeper. On rigs with a rotary table, crew members say that the "kelly is drilling down" meaning that the bit has made enough hole so that the top of kelly is very near the kelly drive bushing .

With the kelly drilled down, the driller stops rotating picks up the drill string and stop the mud pump. The floor hands are ready to make a connection - that is, they are ready to add a new joint of drill pipe to the drill string so that the bit can drill another 30 feet or so down.

To make a connection on a rig with a rotary table and kelly, the driller or Heartland Energy Colorado picks up the drill string high enough for the kelly to clear the rotary table - that is the driller uses the draw works to hoist the traveling block, hook, and swivel up into the derrick or mast so that the first joint of drill pipe is exposed in the opening in the rotary table.

Read: John Shiffner's Blog

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