As we discussed earlier, barefoot completions normally target hard, consolidated reservoir rocks. Wells in reservoirs that are susceptible to sand production will require different well completions. For wells requiring sand control, we can use Open-Hole Slotted Liner Completions, Open-Hole Screen Completions, or most commonly, Gravel Pack Completions.
A liner is a casing string that does not go to the surface. A typical Cemented Liner Completion is shown in Figure 7.09 (A). This particular completion does not offer any sand control capability but is included here to introduce the concept of a liner. As we can see from this figure, the liner does not go to the surface but is hung from a Liner Hanger. The cemented liner completion has many of the advantages of a Cased and Perforated Completion (to be discussed) but at a reduced cost. Because the liner in this completion is cemented in-place, (A) it does not represent an open-hole completion and (2) it requires perforations for the well to access the reservoir.
The other completion in Figure 7.09 (B) either the Slotted Liner Completion or the Screen Completion, is an open-hole completion and does offer some sand control capability. Note that we have not cemented the slotted liner or screen set across the reservoir, so these are open-hole completions, but not barefoot completions.
A slotted liner is a liner with pre-milled slots, while a screen is a liner with pre-milled holes. These liners do not require perforations to achieve access to the reservoir. Figure 7.10 provides a more detailed illustration of these liner types.
There are many applications for slotted liners and screens but in the context of this discussion, they provide partial sand control with the physical dimensions of the openings acting as filters against the sand production. This sand control, however, is limited because the openings may eventually plug, causing a reduction in the oil rate.
The most common method of sand control is with gravel pack completions. Two examples of gravel pack completions, one cased and perforated completion and one open-hole completion, are shown in Figure 7.11. In these completions, gravel is placed either between a slotted liner (or screen) and the casing (or sandface) to act as a filter for the formation sand.
The gravel is selected to have good permeability so as not to create a significant pressure drop through the gravel pack and to have good filtering capability. This gravel is often treated with resin to improve its filtering capability.
There are many variants to the gravel pack, such as pre-packed liners or screens (two concentric slotted liners or screens with gravel pre-packed between them) or frac-pack (combination of hydraulic fracturing and gravel packing . This further illustrates the need for the production engineer to work with the oilfield service providers and manufacturers to be aware of all technology innovations. In fact, a significant portion of the production engineer’s time is working with the service companies and manufactures to develop solutions for the completion needs of their wells.
I have included the link to an article from the Schlumberger Oilfield Review with a lot of good information on sand control and frac-packing:
 Schlumberger Oilfield Review: Frac Packing: Fracturing for Sand Control