fl uids and disposed of. Although the exact cost is diffi cult to quantify, experts agree that produced sand costs the oil and gas industry tens of billions of dollars annually. Sand production has always been a problem, but the manner in which the exploration and production (E&P) industry manages this prob- lem has become more sophisticated. This article briefly reviews the basic principles of sand production and the technologies available to help predict, prevent and monitor sand produc- tion. Case studies show that sand management is best achieved when operators understand sand- production mechanisms within the reservoir and use an informed decision-making process to select the appropriate technologies and methods for addressing the problem.
The Nature of Sand Production
Understanding why reservoirs produce sand is the crucial fi rst step toward managing sand pro- duction. The installation of downhole completion
hardware may represent an important part of the solution, but greater knowledge engenders a more thorough and longer-lasting solution. For example, the ability to model and predict the sand-production tendencies of a reservoir allows engineers and scientists to move beyond a trial- and-error methodology to resolve sanding issues. A successful sand-management strategy can start during the drilling stage and carry through to reservoir depletion. In the subsurface, the main factors that control whether a reservoir will fail mechanically are rock strength, the effective stress on the formation— a combination of principal earth stresses acting on the rock minus pore pres- sure— and the stresses introduced by drilling, completion and production.3
Rock strength can
be determined through laboratory uniaxial and triaxial tests, and can be represented graphically by a failure curve, or envelope. The shear and normal stresses on a specifi ed plane under three perpendicular principal stresses are determined
by using Mohr’s circle. To determine the condi- tions at which failure occurs, the Mohr-Coulomb failure model is used to relate principal stresses and pore pressure to the cohesion and internal
1. Fjaer E, Holt RM, Horsrud P, Raaen AM and Risnes R: Petroleu m Related Rock Mechanics, Developments in Petroleum Science, 33. Amsterdam, The Netherlands: Elsevier Science Publishers B.V. (1992): 257– 267.
2. Selfridge F, Munday M, Kvernvold O and Gordon B:
“ Safely Improving Production through Improved Sand Management,” paper SPE 83979, presented at the SPE Offshore Europe 2003 Conference, Aberdeen, Scotland, September 2– 5, 2003.
3. Desroches J and Woods TE: “ Stress Measurements for Sand Control,” paper SPE 47247, presented at the SPE/ISRM Eurock 98, Trondheim, Norway, July 8– 10, 1998.
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