Drilling oil and gas wells By

Dr: Taher El-fakharany

2

During drilling operations, drilling fluid is circulated through the bore hole.

Relatively, drilling fluid with low temperature is pumped down into the drill string and upward to the surface, through the annulus.The drilling fluid is heated by formation temperature.The fluid coming out from the well has a higher temperature than the fluid pumped into the drill string. When drilling fluid circulation is stopped, formation and drilling fluid temperatures tend to return back to the original rock temperature.

Drilling fluids circulation

Mud circulation system the drilling fluid is continuously circulated down inside the drill string through nozzles of the bit, and up word in the annular space between the drill pipe and the bore hole.

3

4

After discovering oil or gas it is necessary to extract them from the bottom of the hole up to the surface to make them available for processing and consumption. general requirements of drilling methods: A means of fracturing or abrading the rock formations

A means of excavating the cuttings from the bottom of the hole as drilling proceeds

A means for preventing the walls of the well from caving and for sealing off water or gas.

5

Oil wells vary in diameter within wide limits.It is usually necessary to decrease the diameter of a well progressively as the depth increases , in order to provide adequate clearance for the drilling tools and to permit the entrance of casing to line and excluding water. The initial diameter of the casing depending upon: The depth to be attained The number of reductions in diameter necessary

The size with which it is considered desirable to finish the well.

How a well bore is drilled hole diameter and pipe diameter

Surface

Conductor/stovepipe

Surfacecasing

Intermediatecasing

Productioncasing

Productionliner 6

7

The maximum depth to be penetrated depend upon:

The character of the formations to be penetrated;

The size and weight of the equipment used;

The power available; and The skill of the driller. The depth to which it is profitable to drill is the determining factor in most drilling operations.

8

The economic limit of depth varies with:

The quality of the oil; The prevailing selling price; The productivity of the well; The cost of drilling, and other factors.

9

Rotary drilling:In the rotary method, the formations is drilled by rotating all the drill string, then this rotation transmitted to the bit ,by WOB the formation will be fractured.

During drilling new interval or sections , new joints must be added as drilling progresses.

The cuttings are lifted from the hole by the drilling fluid which is continuously circulated down inside the drill string through nozzles of the bit, and up word in the annular space between the drill pipe and the bore hole.

10

Making a connection:The process of adding a new joint of pipe to the drill string consists of the following steps: Bringing the single pipe from pipe rack and lowering it in mouse hole,

raising the kelly above the rotary table, setting slips around the drill string and then breaking the kelly , kelly bushing and swivel from the top most joint, and stacking them in mouse hole.

stabbing the added single joint into top joint of drill pipe.

After the single joint is added it is ready to drill new section.

11

mouse hole

kelly

rotary table

A device used to grip the drillstring in a relatively nondamaging manner and suspend it in the rotary table. This device consists of three or more steel wedges that are hinged together, forming a near circle around the drillpipe. On the drillpipe side (inside surface), the slips are fitted with replaceable, hardened tool steel teeth that embed slightly into the side of the pipe. The outsides of the slips are tapered to match the taper of the rotary table.

Slips:

Making a trip

13

14

15

Sometimes the drill pipe must be removed from the hole in order to replace the bit.

The pipe is pulled in stands of (2- 4) joints each, mainly the stranded is 3 joints.

drill pipe ranges• Range 1 # from 18 to 22 ft• Range 2 # from 27 to 30 ft • Range 3 # 38 , over.• The standard length used 30 ft. then one stand =90 ft.

Drill pipe is a tubular steel conduit fitted with special threaded ends called tool joints (short cylinder peices attached in both ends). The drillpipe connects the rig surface equipment with the bottomhole assembly and the bit, both to pump drilling fluid to the bit and to be able to raise, lower and rotate the bottomhole assembly and bit.

Drill pipe:

A component of a drillstring that provides weight on bit(WOB) for drilling. Gravity acts on the large mass of the collars to provide the downward force needed for the bits to efficiently break rock.

Drill Collar:

Drill collar

Drillpipe

18

The End of Lecture Four