Sand Production
Sand is
produced as a result of failure of the formation rock and subsequent
mobilisation of the failed material (Tovar and Ibukun 2015). Sand production
can lead to production decline as a result of plugging of screens and gravel
packs, damaging of pumps and other downhole equipment, erosion of tubing and
surface facilities, and in severe conditions loss of the well can occur (Abass,
Nasr-El-Din and BaTaweel 2002). The figures below show some damaging effects of sand production.
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| Sand produced into a separator (gekengineering.com) |
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| a.) screen erosion; b.) surface choke erosion (Matanovic, Cikes and Moslavac 2012) |
Predicting
Sand Production
A number of
sand failure models have been developed for predicting sand production.
Examples of such models are that by Abass, Nasr-El-Din and BaTaweel
2002; and Vaziri et al. 2006.
Sand Control Methods
The major
sand control methods used in the industry are briefly described in the
following:
1.) Restricting Production Rate:
This is a passive method that involves restricting
the well’s flow rate to a level where sand production is at an acceptable rate.
Reducing production rate reduces the drag forces on the sand grains (Cholet
2008). The setback of this method is that the maximum sand-free flow rate is
usually less than the well’s flow potential, leading to a significant loss in
productivity and thus revenue
2.) Selective Perforation:
This involves perforating only the strong intervals with
low sanding tendencies. However, the weaker sands are usually the most
productive and this method will reduce well productivity. Also, there is a
requirement for the strong intervals to be physically connected to the most
productive intervals (Bellarby 2009).
3.) Oriented Perforating:
This involves perforating in the direction with the least
sanding tendency based on knowledge of the stress distribution around the
wellbore (Sulbaran, Carbonell and Lopez-de-Cardenas 1999). Perforation
orientation is along the direction of maximum formation stress (Bellarby 2009,
Benavides et al. 2003).
4.) Increasing Flow Area:
Perforation shot density and size can be increased in
cased-hole completions to reduce the flow velocity at the well bore below that
required for sand production (Matanovic, Cikes and Moslavac 2012).
5.) Open-hole Standalone Screens (OHSAS):
In OHSAS, sand screens serve as downhole
filtration media for preventing sand production into the wellbore. Exclusion of
sand relies upon the formation of a physical bridge over the opening of the
screen. OHSAS have suffered significantly high failure rates especially in
non-uniform poorly sorted sands. This generally results from plugging of the
screen leading to decreased area of flow and consequently, erosion of the
screens at ‘hotspots.’
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| (Weatherford 2001) |
6.) Gravel Packing:
Gravel Packing involves placing gravel within the annulus between the
screen and the producing interval where it serves as the primary mechanical
filtration media. Gravel Packing is the most popular sand control method with
more than 90% of all sand control completions being gravel packs (Petrowiki
2015).
7.) Frac Packs:
This is a combination of hydraulic fracturing and gravel packing.
Fracturing is achieved by pumping a high viscosity fluid above the formation
fracture pressure. Proppants are then placed in the fractures created. This
technique provides a combination of the benefits of production enhancement of
hydraulic fracturing, and sand control associated with gravel packing
(Schlumberger 2007). Frac pack requires more complex fluids, and mixing and
pumping equipment.
8.) High Rate Water Packs (HRWP):
HRWP is a cased-hole gravel pack technique where water
is used as the gravel carrier fluid. The water pack is performed above the
formation fracture pressure. This is not aimed at stimulating the reservoir but
to ensure good packing of the perforations with gravel. Water as the carrier
fluid ensures high leak off through the fractures, limiting the distance of
fracture propagation. HRWP completions have been linked to pack permeability
damage caused by fines invading the pack and migrating towards the wellbore
(Ali, Vitthal and Weaver 2000).
9.) Chemical Consolidation:
This technique involves treating the formation in the
near wellbore area to improve the bonding of the formation sand grains. Resins
are the most commonly used chemicals for sand consolidation and their use
requires careful chemical handling. Formation damage caused by the
consolidation process can cause an area of reduced porosity and permeability,
hence reducing productivity.
Selecting a Sand Control Method
Selection
of the appropriate sand control method to be applied in any field development
depends on a variety of factors. Some of these are:
- Cost
- Required well productivity
- Reservoir geomechanics: sanding tendency and sanding rate prediction
- Well geometry or deviation: e.g. challenge with horizontal gravel packing
- Reservoir fluid properties
- Expected life of well and well intervention plan
- Allowable sand production rate
- Location: easy mobilisation of equipment and personnel; deepwater
- Technical expertise and experience from offset wells.
An integrated
sand management approach that combines both active and passive controls with
considerations to the specific requirements of the well, should be adopted in
selecting the appropriate method. Oyeneyin (2015) is a good reference for an
integrated approach to sand management.
References
ABASS, H.H., NASR-EL-DIN, H.A. and BATAWEEL, M.H., 2002. Sand Control: Sand Characterization, Failure Mechanisms, and Completion Methods. Society of Petroleum Engineers.
ALI, S., VITTHAL, S. and WEAVER, J., 2000. Improvements in High-Rate Water Packing with Surface-Modification Agent. Society of Petroleum Engineers.
BELLARBY, J., 2009. Developments in Petroleum Science, Volume 56 - Well Completion Design. Elsevier.
BENAVIDES, S.P. et al., 2003. Advances in Horizontal Oriented Perforating. Society of Petroleum Engineers.
CHOLET, H., 2008. Well Production Practical Handbook (New Edition Expanded). Editions Technip.
MATANOVIC, D., CIKES, M. and MOSLAVAC, B., 2012. Sand Control in Well Construction and Operation. Berlin, Heidelberg: Springer Berlin Heidelberg, Berlin, Heidelberg.
OYENEYIN, M.B., 2015. Integrated Sand Management For Effective Hydrocarbon Flow Assurance. Developments in Petroleum Science, 63
PETROWIKI, 2015. Sand control techniques. [online] Texas: Society of Petroleum Engineers. Available from: http://petrowiki.org/Sand_control_techniques [Accessed 22 June 2015]
SCHLUMBERGER, 2007. Frac packing: Fracturing for sand control. [online] Texas: Schlumberger. Available from: http://www.slb.com/~/media/Files/resources/mearr/num8/37_49.pdf [Accessed 24 June 2015]
SULBARAN, A.L., CARBONELL, R.S. and LOPEZ-DE-CARDENAS, J.E., 1999. Oriented Perforating for Sand Prevention. Society of Petroleum Engineers.
TOVAR, J. and IBUKUN, O., 2015. Bridging the Gap between
Predictions and Reality for Sand Production Prediction. Prediction versus
Reality. 26 March 2015. Aberdeen: Sand Management Network.
VAZIRI, H.H. et
al., 2006. Sanding: A Rigorous Examination of the Interplay between
Drawdown, Depletion, Start-Up Frequency and Water Cut.
