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This paper takes a novel approach towards designing and managing the architecture and operating protocol of injection/production system. The shut-in valve positioning and timing of valve closure control the amplitude and frequency of pressure waves generated during shutdowns. The proposed approach provides the means for mitigating the negative impact of water hammer on the integrity of the near wellbore region and provides an idea of the intensity of any cross-flow issues. It is based on a comprehensive model that examines the fast wellbore transients (water hammer) generated by routine or emergency shutdown of injector or producer wells, which can also cause interaction with a near wellbore region of reservoir. The modeling handles the coupling of the conventional transient pipe flow hydraulics with the transient reservoir flow. The decompression wave created by shutting down an injector interacts with the near wellbore region that induces a transient flow back from the reservoir which creates a risk of mechanical damage by dislodging and transporting material with the fluid movement and even result in sand production. The compression wave created by shutting down a producer may induce repeated injection pulses. In both producing and injection cases, multiple cross-flow phenomena can be triggered between formation layers and wells interconnected within the injection or production system. The analyses of these transient phenomena help to potentially quantify the mechanical damage, which may be induced in near wellbore reservoir region, and assess the potential damage risk associated with produced solids. IntroductionThe effect of water hammer on sand production in water injection wells and its detrimental impact on injectivity has been discussed in multiple publications 1-9 . The basic observation supported by field studies is that the bottomhole pressure drop induced by a pump shutdown or a valve closure can cause formation failure generating loose material. These solids can be produced and transported into the wellbore during bottomhole pressure oscillations associated with the water hammer pressure pulse's round trips. Larger solid particles usually settle inside the rat hole (sump) but small particles stay suspended with the fluid movement 2, 8 . Therefore these solids can induce formation damage due to natural or forced cross-flow between formation layers where injectivity contrast exists or during reestablishment of injection. Other potential damage mechanisms include the perforation tunnel collapse, the loss of rock cohesion near wellbore followed by the injectivity reduction, and the between well cross flow with transport of produced solids between injectors through manifolds or pipeline 5 .The schematic of fast transients responsible for cross-flow and formation damage in water injection system under subsea environment is shown in Figure 1. The system involves a riser (1-2), a manifold (2) connected with two injectors B01 and B02. In the case of FPSO pump shutdown, the water hammer manifestations may be ...

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