Well completion

Well completion

Do you think a well is ready for production as soon as it's drilled?

Well completion is the phase that comes after the drilling of 
a well but before the well is used for production. 
The process of well completion involves a group of operation
 that extends beyond simply installing well bore 
tubular & well completion equipment. 
In fact the well completion process includes:

1-    installing & cementing

2-    running production tubing

3-    Perforating a well

4-    cleaning up or testing

Occasionally the completion design can be affected by factors
 such as a complex 
wellhead or any processing storage requirements
 affecting productivity.

Completion engineers used 2 main industrial terminologies:

1-    lower completion for the part across reservoir
sand face that includes perforation,
 flow control valves & permanent monitoring

2-    Upper completion for part above packers' assembly that 
includes safety valves, gas lift mandrels,
 tubing & wellheads.

There are 3 basic requirements that any well completion must meet.

 A well completion system must be

1-    efficient in terms of meeting all the production objectives

2-    safe in terms of a secure well environment

3-    economic in terms of the profit generated over the cost incurred

Based on the completion objectives, well completion is divided into 3 basic styles. 
These are

1-    temporary

2-    permanent

3-    workover

         The table below displays the difference between the different 
          styles of well completions

         Well completion:' its significance in productivity'

         The significance of well completion lies in the fact that it is the
         only productivity factor, amongst three, which can be influenced by 
         man to increase productivity. 
         The two other productivity factors namely Reservoir Boundary 
         & Reservoir  properties are natural factors over which man 
          has no control. 

       

 Well completion & skin effect

        While designing well completion factor that must be taken into
           consideration is   the skin effect. 
           Skin has a direct impact on well productivity which can
           be +ve or –ve.  Skin is the change in radial flow geometry near
            the well bore caused by flow
           convergance, wellbore damage, perforation, partial penetration and 
          deviation. The effect of skin can be seen as a pressure drop across 
          the completion this drop in pressure results from reduction in total 
          pressure available to bring fluids from a distance R_e to the well 
          bore at distance R_w.the pressure at distance R_e from the well
          bore axis is the undisturbed reservoir pressure.P_ewhrer as the 
          pressure at a distance R_wfrom the well bore axis is the well
          bore pressure  P_wf. the resultant pressure drop is the draw down 
         that causes movement of fluids from a distance R_e to the distance R_w

         There are different ways to maximize the productivity. These include:

        1-    creating highly conductive path to the well bore by fracturing the formation

        2-    reducing the viscosity by employing methods such as steam injection

       3-    removing skin by employing methods such as acidizing

        4-    increasing well penetration by perforating deeper into the formation

        5-    reducing formation volume factor by choosing correct surface separator

 

        Types of well completion:

            1-    open hole completion

            2-    cased hole completion "in which we use perforation"

            3-    slotted linear completion

            4-    gravel back completion