RIASSUNTO
Abstract
This paper discusses the development and the recent, successful application of downhole vibration technology as an effective, economical technique for extracting sand- and gravel- stuck tubing, pipe, and liners from wellbores. This paper shows how equipment previously considered immovable can be extracted by applying low-frequency vibration at the point where it is stuck. Furthermore, the paper describes how downhole vibration fills a technological gap between single impact jars, washovers, milling operations, and surface vibration, accomplishing these extractions at considerable cost and time savings over other approaches. Testing and field runs in which liner lengths ranging from 60 to 725 ft were successfully extracted are presented, demonstrating the efficiency of the new technology. Application identification also is addressed.
Introduction
The occurrence of stuck pipe has been observed in the industry since man first drilled or bored holes in the earth. We have faced this problem of tools becoming stuck in the hole, obstructing drilling and workover progress. At times, this can cause an operator to side track, abandon or move off for a period of time, which in turn is lost time and lost production. This industry-wide problem has been estimated to cost operators over one billion dollars per year in lost rig time, lost production, and the cost of fishing operations and lost tools. It has caused them to re-drill or abandon wells1,2. Many conditions can cause objects to become stuck in a wellbore: differential sticking, under gauged hole, poor hole cleaning, mechanical sticking. But most stuck pipe occurrences have been attributed to human error. In this paper, our main focus is on gravel-packed liner removal and sand stuck liners and tubing. Further development and testing of downhole vibration tooling for an open hole environment are needed to address the above mentioned items.
Current technologies to recover stuck objects consist of but are not limited to: impact tools (jars), washover operations, and milling tools. All of these operations have been in the industry for many years and have a varied success rate depending upon time allowed. In a jarring operation, you may possibly recover a stuck object within a matter of minutes to possibly days of rig time. Washover and milling operations can also consist of many days of rig time depending upon the fish to be removed. You also have additional risk factors that should be evaluated during washover and milling operations: type of sticking, hole cleaning capabilities, hole angle, depths, material to be removed.
In the late 1980s, Tri-State Oil Tools started working with Mr. A.G. Bodine on vibration technology. Mr. Bodine obtained United States Patent 2,972,380. It became the basis for stuck tubular extraction utilizing vibration. Starting in 1991, Tri-State Oil Tools began the operation of what is today called the ""Surface Oscillator"" or ""Surface Resonance Tool"".
Although the tool allows for remote operation, its 120,000-lb hook load limits depth. The Surface Oscillator is a portable tool consisting of four main components: oscillator, power pack, hydraulic hoses, and control panel, although you must also have a special work string.
With a success rate exceeding 90% in recovering liners, tubing, and drill pipe ranging in lengths of 30 to 700+ feet, the Surface Oscillator or Resonance Tool became a new method for operators to save rig time and cost of rental equipment (i.e., jars, drill collars, handling equipment, drill pipe or work strings and fishing tools).
A typical job for the surface tool would take only a matter of minutes to free the stuck object. Should the stuck liner or tubing not become free within 30 minutes, additional measures would be applied.