- Title : Completion Technology for Unconsolidated Formations [ pdf ]
- Publish : Refferense by Coberly, C.J., “Selection of Screen Openings for Unconsolidated Sands”, API Drilling and Production Practice, 1941. Penberthy, W.L. and Echols, E.E., “Gravel Placement in Wells”, SPE Paper 22793, Journal of Petroleum Technology (July 1993) and Penberthy, W.L. and Shaughnessy, C.M., Sand Control, SPE Series on Special Topics, Volume 1, 1992.
- Type Document : pdf
- Release : June 1995
- Total Page : 256 Page
- Size : 5.32 Mb
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Decrypted Contents
CAUSES AND EFFECTS OF SAND PRODUCTION
Completion Technology for Unconsolidated Formations 2-1
Introduction
Chapter 1 addressed radial flow through porous media and showed the nature of the pressure distribution around a producing well. Negative effects on productivity caused by flow restrictions on the near wellbore area have been described. With the concepts of radial flow and formation damage understood, the problems unique to unconsolidated formations can be explored.
In highly unconsolidated formations, the production of formation fluids will probably be associated with the production of formation sand. In some situations, small quantities of formation sand can be produced with no significant adverse effects; however, in most cases, sand production leads to reduced productivity and/or excessive maintenance to both downhole and surface equipment. Sufficient sand production may also cause premature failure of the wellbore and well equipment.
Completion Technology for Unconsolidated Formations 2-1
Introduction
Chapter 1 addressed radial flow through porous media and showed the nature of the pressure distribution around a producing well. Negative effects on productivity caused by flow restrictions on the near wellbore area have been described. With the concepts of radial flow and formation damage understood, the problems unique to unconsolidated formations can be explored.
In highly unconsolidated formations, the production of formation fluids will probably be associated with the production of formation sand. In some situations, small quantities of formation sand can be produced with no significant adverse effects; however, in most cases, sand production leads to reduced productivity and/or excessive maintenance to both downhole and surface equipment. Sufficient sand production may also cause premature failure of the wellbore and well equipment.
Nature of Sand Production
The conditions which can cause sand production and the probable condition of the formation outside of the casing after sand is produced can be determined by the factors that affect the beginning of sand production. These factors must describe both the nature of the formation material and also the forces that cause the formation structure fail. The strength of a sandstone is controlled by:
The conditions which can cause sand production and the probable condition of the formation outside of the casing after sand is produced can be determined by the factors that affect the beginning of sand production. These factors must describe both the nature of the formation material and also the forces that cause the formation structure fail. The strength of a sandstone is controlled by:
- The amount and type of cementing material holding the individual grains together
- The frictional forces between grains
- Fluid pressure within the pores of the rock
- Capillary pressure forces
The type of failure that is likely to occur in sandstone has been investigated by several researchers. Work at Exxon1 indicates that the nature of a failed perforation tunnel is indicative of a shear failure that will occur when the compressive strength of the rock is exceeded. In addition, the Exxon work indicates that in weakly consolidated sandstones, a void is created behind the casing. Exxon concluded that the rock’s compressive strength should be a good indicator of sand production potential, and that sand production will probably cause a void behind the casing that can be filled with gravel pack sand during a gravel packing operation. The details of the research work performed by Exxon may be found in Reference 1.
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