Page 258 - Hydrocarbon Exploration and Production Second Edition
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Well Dynamic Behaviour                                                245






















                       barefoot  pre-drilled or  cemented  open hole  cased hole
                                 slotted liner   &       sand control  gravel pack
                                              perforated  screens/       or
                                            liner or casing  gravel pack  frac-pack
             Figure 10.16  Reservoir completion summary.


             block production or produce solids to surface. However, on the upside, there is
             a large flow area and some future interventions such as sidetracking to a new
             reservoir location are relatively simple as there is no equipment in the way. Barefoot
             completions are common in land locations – especially those producing from
             competent limestones and dolomites.
                The pre-drilled or pre-slotted liner is slightly more complex. The liner has holes
             or slots milled in it before it is installed. It is still an openhole completion in
             that whatever is drilled is open to production. The liner however will stop the hole
             from totally collapsing and aid in getting intervention or logging tools down. It
             is however usually impossible to make the slots small enough to stop individual
             grains of sand from being produced. These types of completions can use openhole
             packers in order to isolate water or gas intervals. An application of these in a
             horizontal well is shown in Figure 10.17.
                These openhole packers are either inflated or can be designed to swell once in
             contact with reservoir fluids. They then provide a location for setting plugs or
             straddles when needed.
                The cemented and perforated liner is more complex still, but has distinct advantages.
             The casing or liner is run across the reservoir section and cemented in place. Once the
             cement has set the well can then be perforated – typically running the perforation guns
             on drill pipe. Alternatively the upper completion can first be run and then the
             perforations run through the completion – typically with electric line. The perforation
             guns contain many shaped charges. In each shaped charge (Figure 10.18), there is a cone
             of explosive. When detonated, this sends out a high-pressure unidirectional jet which
             punches through the casing, the cement, and several feet into the formation.
                Once at the correct depth the gun (as shown in Figure 10.19) is fired from surface
             usually either by electric cable or by hydraulic pressure. The big advantage of a
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