Summary
Long horizontal-section wells are economical requirements for heavy-oil
fields in deepwater environments. This article discusses the operational limits
for gravel-pack placement in such wells in consideration of the maximization of
the horizontal-section extension in low fracture-gradient scenarios. A
parametric study on the variables governing the gravel-pack operations
indicates that careful hydraulic design and detailed operational procedures can
guarantee a successful job. Alternative strategies are proposed to extended
hydraulic limits in critical conditions.
Introduction
The new scenario for offshore development in Brazil includes heavy-oil
fields in deep waters in which 1,000- to 2,000-m horizontal-section wells are
required. Because of the nonconsolidated formations found, sand-control
techniques are required in the Campos basin, offshore Brazil. Sand production
results in several surface problems, such as equipment erosion and
sedimentation inside the oil/gas/water separator.
There are many techniques for sand control available in the petroleum
industry. Economic development of deepwater projects requires that a minimum
number of wells be drilled and requires getting effective reservoir drainage to
maintain a high-productivity index of the wells.
An important option for accomplishing this task is to drill horizontal
wells. Openhole gravel packing of horizontal wells in unconsolidated formations
is a very effective way to achieve adequate sand control.
The gravel-packing technique consists in filling out the annular space
between screen and producer formation with sand or ceramic particles with
selected grain diameter. The idea is to create a second porous medium with a
pore-throat diameter smaller than the formation-grain diameter, and as in this
case, fluid would easily flow through the gravel pack while formation particles
would not. Tiffin et al. (1998) define the relevant criteria for gravel-pack
sizing.
Because of critical conditions, such as the deep- and ultradeepwater and low
frac gradients, precision is required to ensure gravel-packing success. Most
models available in the industry for horizontal gravel-pack design are
essentially empirical, resulting in imprecise predictions for extrapolated
conditions.
These aspects were the main motivators for a research project including
theoretical and experimental development. This paper presents a comprehensive
methodology of gravel-pack design, extending the applicability of the
gravel-packing technique for longer horizontal wells.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
16 November 2004
- Revised manuscript received:
13 April 2006
- Manuscript approved:
28 April 2006
- Version of record:
20 September 2006
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