Casing Selection Burst and Collapse

Casing Selection Burst and Collapse
  • Casing Selection Burst and Collapse

  • Views 25

  • Downloads 0

  • File size 78KB
  • Author/Uploader: zapspaz

CASING SELECTION- BURST AND COLLAPSE admin | November 26, 2009 | Comments (0) CASING SELECTION- BURST AND COLLAPSE It is customary in casing design to define the load case for which the casing is designed for. There are several load cases which arise due to drilling and production operations … However before a load case is applied, the casing grades/weights should initially be selected on the basis of burst and collpase pressures, then load cases should be applied.If only one grade or one weight of casing is available, then the task of selecting casing is easy. The strength properties of the casings available are compared with the collapse and burst pressures in the wellbore. If the design factors in collapse and burst are acceptable then all that remains is to check the casing for tension. For deep wells or where more than one grade and weight are used, a graphical method of selecting casing is used as follows: 1. Plot a graph of pressure against depth, as shown in Figure 5.5, starting the depth and pressure scales at zero. Mark the CSD on this graph. 2. Collapse Line: Mark point C1 at zero depth and point C2 at CSD. Draw a straight line through points C1 and C2 For partial loss circulation, there will be three collapse points. Mark C1 at zero depth, C2 at depth (CSD-L) and C3 at CSD. Draw two straight lines through these points. 4. Burst Line:Plot point B1 at zero depth and point B2 at CSD. Draw a straight line through point B1 and B2 (see Figure 5.5). For production casing, the highest pressure will be at casing shoe. 5. Plot the collapse and burst strength of the available casing, as shown in Figure 5.6. In this figure, two grades, N80 and K55 are plotted to represent the available casing. Select a casing string that satisfies both collapse and burst. Figure 5.6 provides the initial selection and in many cases this selection differs very little from the final selection. Hence, great care must be exercised when producing Figure 5.6.