Workover Well Control Manual
This two-volume set of books encompasses well production operations from the time the first potential oil or gas horizon is penetrated until the well is abandoned. Primary focus is on well completions, workovers, and stimulation, which are critical to producing operations. The objective of completing a well is to obtain, and to maintain effective communication with the desired reservoir fluids and is the focal point of exploration and production activities. The technology required for effective well completion is very complex. The importance of total reservoir description is emphasized including geology and fluid flow characteristics, the role of communication between the reservoir and the wellbore, the pitfalls of flow restriction around the wellbore, and the importance of knowing where fluids are and in which direction they are moving. Problems are involved in excluding undesired fluids.
Waterflooding and other enhanced methods are used to maximize recovery of hydrocarbon fluids. Topics included in Volume I are: geologic considerations, reservoir considerations in well completions, well testing, primary cementing, well completion design, tubing and subsurface control equipment, perforating oil and gas wells, and completion and workover fluids. The conventional rig, the most widely used rig for workovers, performs several common functions: tripping in and out of the hole, rotating the work string, and circulating fluid. Its primary component groups are the derrick, hoisting systems, rotary tools, circulating systems, and tubular goods.
Rig sizing depends on the job requirements; the typical workover rig is a small-capacity, single unit used for concentric work. A workover rig's most important feature is its portability; compartmentalizing the rig permits transporting it offshore in packages smaller than 8000 lb and allows small cranes to replace derrick barges for loading operations. Many workover operations can be completed quickly and efficiently by using coiled tubing instead of jointed tubing or conventional rigs. In general, coiled tubing is a continuous string of small-diameter tubing that can be run into the well without the necessity of making joint connections. The operations are safe, involve small amounts of rig time, and usually are more economical than other forms of concentric work. Coiled tubing work is usually conducted on producing wells, which necessitates pressure-control precautions.
Applications for coiled tubing involve all aspects of workover operations except wire-line work. Coiled tubing can be used in initiating flow, cleaning out sand in tubing, and performing stimulation operations. In addition, drilling can be conducted with coiled tubing when down-hole motors are used.
The primary type of choke now used in well control is the steel adjustable-orifice choke; its advent enabled pressure control in almost all conceivable situations. Such chokes can tolerate any kind of kick fluid for long periods of time and, if necessary, at high pressures. The two most common steel chokes are the Swaco (which consists of two tungsten-carbide plates with 'half-moon' orifices) and the Cameron (which uses a rod-and-cylinder system to develop the desired backpressure). Some of the important considerations in testing blowout-preventer stacks are the test fluids, pressures, equipment, procedures, and frequency.
Workover Well Control Manual
The mud-mixing system should be designed to handle a rapid increase in mud density in order to initiate kick-killing procedures. The mixing system's main components are the mixing pumps and the hopper.