Top Ad unit 728 × 90

random

Slickline Operation: Introduction of Surface Equipment

Slickline Surface Equipment
Pressure control equipment is necessary to enable a slickine operation to be safely conducted on a live well. Specialized systems have been developed for the various types of slickline, braided line and electric wireline used. The desire to gather more information on the reservoir and production characteristics of the completion has encouraged the development of equipment and techniques to enable safe and efficient wellbore access in live and flowing wells. Modern pressure control equipment and techniques began to emerge in the 1940’s and early 1950’s. The original techniques used by electric wireline and slickline service companies were similar to the procedure used to swab in a well.

A line wiper or stuffing box, consisting of a housing at the surface containing a resilient packing material, typically rubber, was used to seal off around the cable. The line wiper was mounted on top of the joint of tubing or pipe, called a lubricator. The lubricator served as a chamber above the wellhead, which the swabbing tools could be pulled into, permitting the swabbed fluids to flow uninterrupted through the flow line. The swabbing tools could then be retrieved while keeping the well pressure and fluids under control. However, this was an unsatisfactory method of controlling moderate to high-pressures because abrasive wear of the rubber seals by the stranded cable permitted well fluids, including oil, water or gas, to escape around and through the cable. This created obvious hazards at the wellsite and surrounding environment.

Following World War II, the industry developed new types of perforating guns using high-energy jet perforating charges. These improvements created a need for more sophisticated methods to contain well pressure. When it was necessary to enter a live well, the trend was to reduce electric line diameters to minimize the amount of weight required for the tools to be lowered into the well against pressure. The force resisting tools going into the hole is directly related to the well pressure acting on the cross-sectional area of the cable. As the well pressures increased, it became necessary to run weight bars with the perforating or logging tools to offset the force of the well pressure.

The friction developed around the cable by a conventional rubber-element stuffing box under pressure was severely limiting. For example, at 5000 psi, it was necessary to add 40 to 50 ft of weight bars to overcome the friction created by the stuffing box. This required a lubricator of 85 to 100 ft in length. Thus, going into the well under pressure became expensive and difficult due to the time and labor required in assembling, erecting, and disassembling a lubricator of this length.
[post_ad]
Early solutions were directed toward the development of sealing devices designed to reduce friction to a minimum so that the only forces involved were directly related to line diameter and required minimum weight. Shell Development Company in Houston, Texas developed the use of grease as a means of sealing around cable and wireline in the 1950’s. The patented concept not only required the use of a grease seal but used a pressure enclosed sheave wheel at the top of the lubricator which was power driven, forcing the cable into the well. The device never became widely used due to the expense and time needed to erect it over the wellhead.

Development of the flow tube followed. This used a controlled blow-by arrangement, within which there was no absolute seal. The flow tube principal relied on the fluid pressure drop from the bottom of the flow tube to the top. Well pressure would be reduced after it coursed through the close fitting turbulence chamber surrounding the cable. The fluid or gas emerged at the top of the flow tube with its energy dissipated to such a degree that the pressure at the top was only slightly more than atmospheric. This fluid was carried off through a drain hose and could be drained into a bucket or exhausted into the atmosphere under controlled conditions. A conventional line wiper was mounted above the flow tube.

The controlled blow-by flow tube became a standard in the industry for pressures up to 5000 psi. At pressures of more than 5000 psi, the device was unreliable and unsafe. The requirement for such high-pressure intervention resulted in the development of modern grease seal control heads. Current technology enables slickline operations to be conducted on oil or gas wells, which have surface pressure in excess of 15,000 psi. These operations can be conducted safely with a positive seal around the wire or cable while allowing relatively high rates of line speed at well depths of over 25,000 ft. Slickline techniques were developed over a period of years, with the first criteria for design being a high margin of safety in the design and operation of pressure control equipment.

Allowing well pressure to enter the lubricator positioned above the wellhead exposes the surrounding area, equipment and personnel to the hazard of possible failure of surface equipment. A high degree of quality control and engineering effort has been devoted to building modern equipment to achieve maximum safety. A major contribution to the increased safety of pressure control equipment is a planned program of pressure testing and inspection of the equipment prior to every job. This is also supported by formal maintenance and inspection procedures.

Deep oil wells frequently encounter more extreme pressures, high temperatures and hazardous well fluids, sometimes with high hydrogen sulfide content, resulting in a need for more reliable pressure control equipment that must operate under more stringent operating conditions. Such severe operating conditions have resulted in the creation of regulations, regulatory bodies and environmental controls to help ensure operations are conducted with safety.
Slickline Operation: Introduction of Surface Equipment Reviewed by Industri Migas on 12:20 AM Rating: 5

No comments:

Thank you for visit and read this post. Share this post if you like it.
Leave your comment on this text box

All Rights Reserved by IndustriMigas | #1 Oil and Gas Blog © 2014 - 2015
Powered By Blogger, Designed by Sweetheme

Contact Form

Name

Email *

Message *

www.industrimigas.com. Powered by Blogger.