Well Completion Type and Application

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There are several ways of classifying or categorizing completion types. The most common criteria for the classification of 
:completions include the following



.Producing zones, i.e., single zone or multiple zone production
Production method, i.e. natural flowing or artificially induced
.(production (artificial Lift
Wellbore/reservoir interface, i.e., open-hole or cased hole
.horizontal completion

The borehole-formation interface differs according to whether the wells are vertical, deviated (up to an angle of 60°-70°), sub-horizontal or horizontal (angle greater than 70°). Traditionally wells have a telescopic casing profile and involve the use of a greater number of casing sizes the deeper the well while maintaining a fixed production casing size. Horizontal wells generally have a borehole that navigates inside the reservoir itself

The interface options for vertical wells can be divided into three main categories: open hole, open hole with non-cemented liners, and cased hole

In the case of an open hole, the production casing shoe is set to the top of the production reservoir which is later drilled and left as an open hole. Generally, this option is chosen in the presence of a single hydrocarbon bearing reservoir when it is constituted by secondary porosity rock. Such method is only applicable to highly competent formations which will not slough or cave-which will
remain in place during production

The principal limitation of this type of completion is that it is impossible to selectively produce more than one level or to exclud
(the presence of undesired fluids (water or gas

:Advantages of Open Hole Completions

  The entire payzone is open to the wellbore-
Perforation expense is eliminated-
Reduce casing cost-
  Expensive log analysis not required-
 -(Maximum wellbore diameter is opposite the payzone(s- reduced-
drawdown 
 The well can easily be deepened-
  Easy conversion to liner or perforated casing recompletion-
  No formation damage caused by cement-
Open-hole completion

:Disadvantages of Open Hole Completions 

 Excessive gas or water production difficult to control because the-
.entire interval is open to flow

 The casing may need to be set before the pay zone(s) are drilled-
.and logged

 Separate zones within the completion cannot be selectively-
.fractured or acidized 

Requires frequent cleanout if producing formations are not-
.completely firm

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