Investigation of Sanding around Water Injector Wells in Unconsolidated and Weakly-Consolidated Sand Reservoir under Water Hammer Pressure Pulsing

• Author / Creator

  Jafar Pour, Mahshid

• This research is focused on massive sand production around injector wells immediately after well shut-in events. Sand production in some water injector wells has been reported to be catastrophic, massive and always occurring after an unplanned shut-in. High pore pressures around injectors, numerous cycles of injection and shut-in, the strength-weakening effect of water and water hammer (WH) induced pressure pulses make the conditions around wellbore susceptible to sandstone degradation and sand production. WH is a general term describing the generation, propagation and damping of pressure waves in pipes. It occurs due to sudden velocity changes occurring upon quick shutting down of the well. There are several examples of massive sand production and even complete injectivity losses. Progressive failure and liquefaction are among the theories to explain massive sanding. However, no numerical modeling has been performed to verify the underlying responsible mechanism. A dynamic analysis together with a suitable constitutive model can help us understand the mechanism, and hence take the necessary precautions to prevent catastrophic sand production conditions. The relevance of the research is not restricted to injection wells. Production wells also deal with WH waves during sudden shut-ins. Sudden sanding can be expected in producers particularly at high water cuts for which low compressibility of the water column in the wellbore ensures low attenuation of the WH pressure pulses. In this research a 2D axsisymmetric, single-phase fluid, sequentially coupled dynamic code is developed, capable of modeling pore pressure waves propagating within saturated porous media. The code ignores cyclic behavior and the effect of fatigue. It is used to study the sanding potential because of dynamic WH waves in a small-scale synthetic case study. The model simulates a layer of both weakly-consolidated and unconsolidated reservoir with the WH waves applied as a boundary condition. The modeling results indicate progressive failure as the underlying mechanism for massive sanding. The stress paths and dominant factors affecting failure and potential sand production are also discussed. The fast changes of stress conditions and failure progression confirms the need for a dynamic analysis.

• Subjects / Keywords

  • Wave Propagation
  • Sandstone Strength
  • Saturated Porous Media
  • Sand Production
  • Water Hammer
  • Dynamic Analysis

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3707X39J

• License

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