Wellheads are manufactured in a vast variety of manners for numerous purposes which dictate design. Factors that affect wellhead configuration are pressure, temperature, location, well depth, well size, well purpose, expected well life, well control equipment interface, drilling method, etc.
A wellhead serves numerous functions. Some of these are:
1) Means of casing suspension. (Casing is the permanently installed pipe used to line the well hole for pressure containment, collapse prevention etc.) 2) Means of casing pressure isolation when multiple casing strings are used 3) Means of attaching BOP (Blow Out Preventor) during drilling 4) Means of attaching a tree for well control during production, injection, or other operations 5) Means of well access 6) Means of pump attachment 7) Means of tubing suspension (Tubing is removable pipe installed in the well)