Summary
Current gravel-packed, slotted-liner completion techniques for wells in
unconsolidated and weakly consolidated sandstone are relatively expensive and
result in greatly reduced operational flexibility. On the other hand, empirical
field evidence (Wilmington, California) demonstrates that sand grains
surrounding the wellbore are cemented and consolidated following injection of
high-pressure (1,600-psi) steam. Effective sand control results without adverse
changes to formation permeability and producibility. Here, sand consolidation
mechanisms are exposed by duplicating, in the laboratory, the governing
geochemical processes. Sandpacks contain typical per-volume concentrations of
concrete resulting from perforating a cased and cemented well. The evolution of
sandpack pore and grain struture is determined using scanning electron
microscope imaging and compositional analyses. Results show that hot alkaline
water injected at rates comparable to field rates indeed results in
grain-cementing precipitates. Casing cement plays a crucial role in that it is
the source of calcium silicates appearing in various pore-lining precipitates.
Conditions for effective sand consolidation are not necessarily
formation-specific, and the process can be altered to improve
cost-effectiveness, flexibility, and longevity of the completion technique.
Introduction
In poorly consolidated and unconsolidated sandstone reservoirs, solids are
sometimes carried from the formation to the wellbore as oil and water flow
toward producers. It is referred to as "sand production." This term is
usually detrimental and should be avoided. Operational problems result,
including extra wear of the pumping units, shorter pipe lifetime, frequent
workovers, loss of well productivity, and waste-disposal issues. Several
remedies are available to the engineer. They include production-rate reduction
(Penberthy and Shaughnessy 1992), physical barriers (Penberthy and Shaughnessy
1992), in-situ consolidation (Prats and Hamby 1965; Davies et al. 1983; Davies
et al. 1997; Davies et al. 2003), and hybrid methods (Penberthy and Shaughnessy
1992; Kruger 1986). No sand-control method is, as of yet, generally
applicable.
We use laboratory experiments to develop a mechanistic understanding of a
novel hot alkaline/steam sand-consolidation technique. This technique has
proved effective empirically (Davies et al. 1997). The mechanisms of mineral
and grain dissolution, precipitation, and consolidation using Wilmington (Los
Angeles basin, California) field cores and quartz sandpacks are described.
Field sands are drawn from the productive, heavy-oil intervals (T and D sands)
of the Tar II-A zone (Hara 2003).
The tools employed are core-scale and beaker-scale experiments, scanning
electron microscopy (SEM), and elemental analyses. Additionally, tubing-tail
samples recovered from the field are reexamined in light of the new laboratory
results. Before proceeding to the experimental details and results, a brief
review of the hot alkaline/steam sand-consolidation process is given. This
background is foundational, because it underpins the experimental program and
interpretation of results. The experimental objectives, apparatus, and
procedures follow. Results, discussion, and implications finish the paper.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
18 January 2005
- Revised manuscript received:
28 October 2005
- Manuscript approved:
28 November 2005
- Version of record:
20 June 2006
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