In order to properly design a completion, reservoir rock and fluid properties must be carefully taken into account because they directly influence on equipment selection. Reservoir properties (rock and fluid properties) which must be considered are as follows;
Low permeability formation may require fracturing operation to enhance production. The completion for tight formations must be able to withstand pumping pressure and allow fracking fluid and proppant to flow through.
Unconsolidated formations are required to complete a well with a sand control completion; thus, a well can be produced without any damage to downhole and surface equipment.
Reservoir pressure directly affects the pressure rating on all completions because all components must be able to work under reservoir condition. What’s more, formation pressure will affect how much flow of the well can produce.
High reservoir temperature will quickly degrade some components, especially elastomer, and this will result in well integrity issues due to pressure leakage. This is one of the critical concerns in selecting the right equipment to work under high temperature conditions. Continue reading
Coiled tubing was developed in 1970s and is one of the most important pieces of well intervention equipment in the oil and gas industry. There are several different types of it available in the industry market with several different designs of a coiled tubing unit; however, the components of a coiled tubing unit are very similar. The main differences are performance capabilities and hydraulic power control systems. This article will give an overview of the essential components of a coiled tubing unit. (Read about the history of coiled tubing here – Introduction to Coiled Tubing (CT) in Oil and Gas)
Figure 1 shows the mounted truck coiled tubing unit, which is normally used for the land operation and Figure 2 is the coiled tubing unit used for operating in an offshore environment.
Figure 1 – Coiled Tubing Unit on a Truck (Courtesy of Stewart & Stevenson)
Figure 2 – Offshore Coiled Tubing Unit (Courtesy of NOV)
Development of the coiled tubing like we know it today started in early 1960’s. Now it is an important component of various workover and service applications. While still the use of Coil Tubing is about 75% in workover/service applications, the technical advancements have resulted in an increase in utilization of Coil tubing in drilling as well as completion applications.
Ability of performing remedial work on live well was an important driver associated with development of Coil Tubing. In order to achieve this feat, there was a need to overcome three different technical challenges: These were:
- Continuous conduit that is capable of being inserted in to wellbore (the CT string).
- Means of running the CT string and retrieving it in to or out of wellbore when under pressure (the injector head).
- Device that is capable of giving a dynamic seal around tubing string (packoff or stripper device)
Coiled Tubing Unit (Credit: ShutterStock)
The Origin of Coiled Tubing Continue reading
Perforation is a special operation to crease an efficient communication path between a wellbore and a reservoir by creating tunnels. The effective paths allow reservoir fluid to flow into the well with minimum pressure loss (less skin as much as possible).
Perforation (Courtesy of Schlumberger)
The process of perforation involves lowering a perforating gun into a wellbore to a planned depth and energizing the gun to be safely fired. When perforating a well, shape charges are fired and then energy from the explosion will create tunnels through casing, and cement and then into a reservoir. Length and diameter of perforation hole are dependent on the objectives which will be discussed later. Figure 1 shows the cross sectional of perforation.
Figure 1 – Perforation Cross Section Ref:http://www.angelfire.com/wy/lisadenke/pictures/assorted_facts_pics/HES_perfs.gif
This article demonstrates how to select material that will be suitable for high pressure, high pressure and corrosive environment. The material chart is based on the Sumitomo tubular chart.
Well conditions are as follows;
Reservoir: High pressure & high temperature gas reservoir
Reservoir Temperature: 420 F (216 C)
CO2 content: 2.9% mol
Chloride Ion Content in Produced Water: 150,000 ppm
Fluid saturation pressure: 10,000 psig Continue reading