Tubular Slotting
Designed for maximum efficiency and manufactured to any specification, Pacific Perforating is the premier provider of slotted liner serving the oil industry in California. On this page you will find some general information about slotted liner. Please visit our FAQs or Contact Us if you have any questions.
- Straight vs. Keystone Slots
- Slot Width and Length
- How to Calculate the Ideal Pattern for Your Liners
What is the difference between straight slots and keystone slots?
Pacific Perforating produces two styles of slots -- either straight or keystone.
Straight Slots
Straight slots are the first type of slots created in liners and they are cut with equal width through the wall of the pipe.
Specified where sand grain bridging at the slot is not of major importance, straight slots are more wear-resistant than keystone slots and are less costly to produce.
Keystone Slots
Keystone slots are milled wider on the pipe interior and are self-cleaning to help prevent plugging. They are narrow at the liner surface and increase in width at the interior, letting sand that does enter pass easily through the slots without plugging. Pacific Perforating's equipment has the capability to produce keystone slotting at an angle of six degrees.
Slot Sizes
Slot Width
Generally speaking, the width of the slots should be some two to three times the diameter of medium-sized sand particles. Our slots range in width from .010 (10,000th) of an inch up to .250 (one quarter) of an inch.
Slot Length
Slot lengths are precision-cut at high production rates and can be matched to your precise specifications in lengths of one and a half to two inches, depending on slot width.
The most common slot lengths consist of:
- 1.5 inches in length on the interior diameter for slot widths up to 0.028 inches.
- 2.0 inches in length on the interior diameter for slot widths from 0.038 to 0.250 inches.
- 2.0 inches in length on the interior diameter for slot widths from 0.025 to 0.028 inches are available on request.
Unless otherwise specified, slotted liners are cut with an even number of rows. This enables the rows to be staggered in order to preserve most of the pipe's original strength and to maintain a 3% open area. When slots are evenly distributed over the pipe surface, drainage is more efficient.
How to Calculate the Ideal Pattern for Your Liners
The number of slots per foot of pipe is determined by calculating the numberrequired to achieve the necessary percentage of open area on the pipe's outer surface.
Calculation of Required Slots Per Foot
After selecting the open area, the slot width and the diameter of the liner, the number of slots per foot of liner can be determined with the formula below or read from the table.
For straight slots, the slot length at the interior diameter (ID) of the liner is used. This gives a conservative calculation of open area. The slot length and open area at the outside diameter (OD) is 25% larger.
For keystone slots, the slot length at the OD of the liner is used. This also provides a conservative calculation of open area because the keystoning results in an open area at the ID of the liner that is over 50% larger than that at the OD.
Example
For example, if an open area of 3% is required, a slot width of 0.020" has been selected to control the sand, and a 4.5" diameter liner will fit in the well, then the number of slots to be cut in the liner is:
