Sand Control 173
Application of OHGP and screen technology
North Sea and Gulf of Mexico fields
High
Likelihood of solids production
Open hole
gravel pack (OHGP)
during well life
Medium
Premium screen only
Screen only
Low
No sand control
Low Medium High
“Quality” of sand (net to gross, sorting, etc.)
Figure 3.32 Application of standalone screens (reproduced by courtesy of C. Bennett and
J. Gilchrist).
below the gravel pack packer was closed by the removal of the washpipe. High-rate,
sand-free results followed.
Most other reservoirs are more challenging than the Harding field. Turbidite
reservoirs, for example, are often characterised by good sorting within some
intervals, but are heterogeneous as a whole. These formations are also a major type
of oil reservoir in areas such as the Gulf of Mexico, the North Sea, and West Africa.
Norsk Hydro, in particular, suggests that Bennett’s guidelines are too cautious
(Mathisen et al., 2007). Due in part to extensive use of very long (up to 10,000 ft
horizontal reservoir sections) and multilateral wells on fields like Troll, they have a
database of 230 completions with standalone screens. Of these wells, 80% use
premium screens, with the remainder split equally between wire-wrapped and pre-
packed screens. Fourteen failures were reported with the majority (eight) associated
with mechanical damage during running of wire-wrapped screens (too much
applied weight and out of gauge holes). Two failures were associated with a gradual
plugging followed by failure. In these cases, the fines content was high either in the
sand itself or in large shale sections. Further failures are attributed to screens being
run in poorly conditioned mud. Interestingly, if the recommendations of Bennett
et al. (2000) had been followed, the relatively poor uniformity (D40/D90 between 2
and 30) and high fines contents would have pushed 75% of the 230 wells to use
open hole gravel packs. They attribute their success to rigorous testing and selection
of the screens and fluid and quality control during installation. No rules are
employed with the selection of the correct technique and screen/fluid combinations
are based entirely on laboratory tests. Their use of inflow control devices (ICDs) on
around 50% of the wells as a means of both reducing coning and increasing sand
control reliability is discussed in Section 3.5.3.
