FIELD OF THE INVENTION
The invention relates to On-shore Oil well drilling Rig in which the pull in and pull
out operation of drill string is carried out by draw-works whereas rimming is
done through a common electrical rotary drive. More particularly, the invention
relates to an independent Rotary Drive Power Control system with redundant
drives for on shore Oil Rig for rotary operation.
BACKGROUND OF THE INVENTION
Depths of Oil wells are typically up to a few kilometers. For drilling operation Drill
string comprises of large number of drill pipes joint together to form drill string
of few kilometers are used in Oil Rig. Drill string is operated by draw work &
rotary. The pull in & pull out operation of drill string is carried out by draw-works
whereas rotation of the same is done through rotary drive. The philosophy used
in Rigs was to have a common drive (Electrical motor and associated controls)
for draw- work as well as rotary operation. The drive was used to be coupled, at
a time, with either draw-work or rotary with rotary clutch arrangement to run the
chain driven rotary. Over the period of time requirement for independent rotary
drive was felt envisaging simultaneous and independent draw-work & rotary
drives operations to improve drilling operation by enabling simultaneous string
movement and rotation and obviate need for shutdown during change from one
drive operation to other. Moreover with chain driven rotary arrangement precise
speed control/adjustment was not possible which is now possible thru direct gear
driven rotary.

Oil Rig generally also has electrical drives for mud pumps depending on number
of mud pump being utilized in drilling Rig. Oil Rig itself is mobile equipment and
is required to be transported to next well location on completion of drilling
operation at one well. Further the rig equipment must be easily transportable,
compact and easy to install during rig building and easy to disconnect during rig
dismantling. In this environment, one of the major constraints associated with
implementation of independent rotary drive was incorporation of suitable
electrical drive armature control system with redundant motor speed control,
required in an Oil Rig. Yet another constraint was incorporation of field supply
system for rotary drive. The other constraint was to incorporate auxiliary starters
required for auxiliaries of drive motor such as lube pumps and blower etc.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an independent Rotary Drive
Power Control system with redundant drives for on shore Oil Rig for rotary
operation.
Another object of the invention is to propose an independent Rotary Drive Power
Control system with redundant drives for on shore Oil Rig for rotary operation,
which is configured as a stand-alone system having redundant controls for IRD-
motor speed control including field supply and starter control.
A still another object of the invention is to propose an independent Rotary Drive
Power Control system with redundant drives for on shore Oil Rig for rotary
operation, which is retro-fittable on new oil rigs without modifications of prior art
drive systems including cooling system.

A further object of the invention is to propose an independent Rotary Drive
Power Control system with redundant drives for on shore Oil Rig for rotary
operation, which eliminates lengthy shutdown and ensures continuity of
operation of the oil rig.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig 1: Shows Topology of Independent Rotary Drive Power Control Room (IRD-
PCR)
Fig 2: Shows General Arrangement of Independent Rotary Drive Power Control
Room (IRD-PCR)
DETAILED DESCRIPTION OF THE INVENTION
As illustrated in Fig 1, major components of IRD-PCR are two units of SCR/VFD
drives controls (1) for redundancy, field supply unit (2), MCC (motor control
center) (3) and lighting and AC transformer (4). MCC has starters(5) with O/L
and earth leakage protection for auxiliaries of IRD Motor, such as lube pumps
and blower. All electrical connections are through plug & socket (6), mounted on
the socket board (14) for ease of rig building/rig dismantling. Out of two identical
drive controls provided one shall be in use at a time whereas the other would be
standby. The drive controls of IRD-PCR can be operated from IRD Control Box
(7) located at driller's position at derrick floor. Motor can be operated and
controlled from IRD Control Box, having facility for drive selection, motor
direction selection and providing motor speed command. The SCR/ VFD drives
receive variable speed command signal from IRD control box. Both drive panels
comprises of ACB, and high speed fuses for protection, semiconductor bridge,
and firing module to modulate the output of bridge based on speed control

command from driller control box. The drive control has circuitry for voltage and
current feedback to control motor speed. Field supply unit, applicable for DC
drive shall have protective fuses, transformer and rectifier unit. Interlocking is
provided to ensure that field supply and auxiliaries are ON prior to motor
armature current is turned on. IRD motor (8) & it's auxiliaries (9) are located at
derrick floor.
As illustrated in figure (2) the above system is containerized in a fabricated IRD-
PCR (10) for weather protection and easy transportability. The PCR is based
upon multi-runner skid (11). At both ends skid shall be provided with two heavy
duty pipes across the whole width with collars (12) for the purpose of lifting and
dragging at oil fields for making cluster well or loading/unloading on trailer for
transportation. Plural walls at sides (13) sandwiched with thermal insulation is
provided for thermal insulation and maintaining inside temperature within limits.
External electrical connection are through sockets installed on socket board (14),
protected by socket board doors (15) serving dual purpose of safety during
transportation and rain protection during operation. During operation socket
board door are kept open and hinge operated rain protection cover (16) rests
over it. IRD-PCR is provided with Air conditioners (17) having 100% percentage
redundancy to keep temperature of electronic controls in safe zone. For safety
two doors (18) with anti-panic lock (19) is provided. ISMC channels (20) are
used as columns to support the fabricated roof assembly (21), filled with thermal
insulation between top & bottom, has gradient at two sides at the top to avoid
water accumulation. Roof assembly is bolted on columns (22) and welded
thereafter on beam (24) for proper strength and perfect sealing. The IRD-PCR is
divided into Air-conditioned zone (meant for electronic equipment & operator)
and non-air-conditioned zone (meant for other equipment and area where
human presence is not envisaged generally) through an insulated wall (23).

WE CLAIM :
1. An independent Rotary Drive Power Control system with redundant drives
for on shore Oil Rig for rotary operation, comprising at least two SCR/VFD
drives controls (1); a field supply unit (2); a motor control center (3); a
transformer (4), and a plurality of plug and sockets (6) for external
connection of the system, wherein the system is installed on a multi-
runner skid (11) having at least two pipes including a plurality of collars
(12) disposed across the entire width of the skid (11), a plurality of side
walls (13) with thermal insulation covering the system on the skid (11),
wherein a socket board (14) having doors (15) including a rain protection
cover (16) is provided, the doors (15) being bolted on columns (22) of the
skid (11), and wherein a plurality of air-conditioners with anti-panic lock
(18,19) including a sloped roof assembly is arranged for safe operation.
2. The system as claimed in claim 1, wherein the MCC(3) comprises starters
(5) for auxiliaries for the IRD motors.
3. The system as claimed in claim 1, comprising an IRD Control box (7).
4. The system as claimed in claim 1, wherein the plurality of plug and
sockets (6) allows easy building /dismantling of rig.