During performance of slick, braided, and electric line service operations on pressurized (live) wells, wireline operators have traditionally employed pressure-control equipment, commonly referred to as lubricator stacks or risers, to control well pressure and fluids. This equipment is temporarily mounted on top of the wellhead as the services are performed. With the maturing of the industry, however, more critical well conditions are now being encountered, and to keep pace with these conditions, nhancements to existing technology have been required to ensure that personnel, property and the environment are protected.
This paper presents an overview of the evolution of wireline pressure control equipment and how the new enhancements can:
increase the safety of wireline operating procedures.
Facilitate the proper selection of equipment for particular well and pressure conditions.
Simplify maintenance requirements of the equipment,
Provide operators with procedures and time frames for regular inspection and maintenance to ensure equipment integrity.
This information is being presented with the hopes that a better understanding of equipment and processes will enable operators to make proper selections of temporary wellhead pressure-control equipment, and thus, ensure safer conditions for both personnel and the environment.
In the 1930's, the process of moving tools in and out a live wellbore using a pressure-control system or stack was developed. This process was originally referred to as "lubricating the tools" into and out of the well, and thus, the pressure-control equipment became known as a "lubricator" or "lubricator slack."
In general, lubricator stacks are manufactured with threaded end connections that employ elastomeric O-ring seals to enable the components to be easily connected without special tools. Equipment working pressures range rom 2,000 to 20,000 psi (13.79 to 137.9 MPa). The components are usually sized to the tubing in the well or the equipment that must be run in the tubing, and the ID sizes range from 2 inches to 9 inches (50.8 mm to 228.6 mm).
Earlier lubricator-stack designs and their components will be discussed first, followed by a discussion on technical enhancements and the increased capabilities of the designs in use today. Finally, a newly-developed maintenance inspection program that can help verify integrity of critical equipment before and during usage will be discussed along with a unique marking system to identify equipment usage.1
The first lubricator stacks consisted of a stuffing box, lubricator sections, wireline valves or blowout protectors (BOP's), and a crossover to the tree connection (Figure 1).2
The stuffing box was used to provide a seal around the slickline as it moved into and out of the well A manual packing nut could be tightened to compress, and thus, energize special packing within the stuffing box to effect the seal. A 10-inch (25.4 cm] OD sheave was used to effect a 180 º bend and to guide the wire into the packing stack.
Lubricator sections were assemb led with lengths and ID's that were sufficient to accommodate the length and diameter of the anticipated tool string that would be run into or pulled out of the well.