By examining the reduced axial force, Fa*, in a casing string, the operating conditions under which the uncemented portion of the casing will buckle are defined. This leads directly to methods of preventing buckling. The axial force is influenced by changes in pressures and temperature that can occur once the string has been constrained by … Fundamental equation for reduced axial force
The onset of buckling does not necessarily mean pipe failure. The acceptability of buckled casing must be assessed in two ways, i.e. the resulting stresses in the casing wall, and the access through the buckled casing for drilling and production tools. Stresses resulting from buckling must be added to those existing in the casing prior … Post-buckling analyses
Casing connections should satisfy several functional and operational requirements which are presented in this article. Functional aspects to provide a leak resistance to internal or external fluid pressures to have sufficient structural rigidity to transmit externally applied loads to have good geometry in order not to increase the outer diameter or reduce the inner diameter … Connection types
In order to ensure the functional efficiency of a connection, even after multiple make-up operations, surface treatments are applied to the box, the pin or to both. The surface treatments are applied to improve: the resistance to galling; the sealing capability; the resistance to corrosion. Below the effect of the different surface treatments on these … Connections Surface treatments
The general accepted method for the qualification of casing connection designs is, at the moment, the conducting of tests on a number of full scale specimens. The aim of such an investigation is to assess the following primary characteristics: the galling tendency; the sealing capacity, the structural load bearing capacity. Qualification Tests The tests to … Connections Testing and qualification
Before casing joints are installed in a well, they are exposed to a variety of harsh conditions during transport, handling and storage. The threaded pipe ends frequently have to withstand accidental impact loading during shipment from the mill to the wellsite and once at the wellsite, during handling, cleaning and running into the hole. In … Casing Thread protectors
When selecting a casing connection the actual load on the connection should be compared to the connection’s capacity. This is applicable for all types of wells: exploration, appraisal and development wells. ·Design load: The load can be derived from the same design loads as laid down for the complete casing string.With respect to the strength … Connections Selection and ordering
Preparation of casing before running serves two purposes. 1. ensure that the pipe body and threads are adequately protected from possible damage when being moved to the drill floor. 2. ensure that handling of the casing on the drill floor is kept to a minimum. These goals can be achieved by use of the following … Preparation for Running Casing
To ensure that the casing is run efficiently to the correct depth and in the desired condition, specific equipment and techniques should be considered in the design phase. 1 Rig hoisting capacity The casing designer should be aware of the hoist capacity of the rig which is to drill the well. Where deep, heavy strings … Running and Testing Casing
Once a casing string has been successfully cemented in place and tested, subsequent operations must be planned to ensure that the casing remains fit for purpose. Condition monitoring systems should be implemented to highlight the potential problems so that timely action can be taken. 1 Drillpipe tool joint hardfacing Tool joint hardfacing on drillpipe should … Monitoring Casing Condition