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SPE 146300

Impact of Water Hammer in Deep Sea Water Injection WellsSuk Kyoon Choi, SPE, and Wann-Sheng (Bill) Huang, SPE, Chevron Energy Technology Company

Copyright 2011, Society of Petroleum Engineers

This paper was prepared for presentation at the SPE Annual Technical Conference and Exhibition held in Denver, Colorado, USA, 30 October2 November 2011.

This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not beenreviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, itsofficers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission toreproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.

AbstractWater hammer is a known pressure pulse or surge that may occur by the instant shut-in of a valve in a flow line. Sudden

momentum change may create a pressure cyclic pulse that could cause damage to valves, bending parts in tubing, and/orjoints. Usually this effect has been well managed in surface facility design; however, it tends to be overlooked in subsurface

well design. Additional possible impact by water hammer in subsurface wells could be on the sandface completions. The

severe water hammer could cause failure of formation integrity, resulting in sand production. It may also damage the

wellbore and downhole completions. Especially for deep sea water injection and/or production operations, water hammer

effect needs to be thoroughly investigated and properly managed because it could be more severe due to longer flow line and

higher flow rate.

The purpose of this study is to have a comprehensive investigation on water hammer effect for an actual water injection

well in Chevrons deep water project with different design parameters and operating parameters. The design parameters

include a) height of vertical riser; b) tubing diameter; c) injectivity index (skin or completion type); d) sandface wellbore

length; and e) well deviation. The operational parameters include a) injection rate; b) closing time; and c) injection watertemperature. Multiphase transient fluid flow model OLGA is used for the water hammer simulation.

Results of the water hammer parameter study for optimum well design and operating strategy are reported here. It isshown that the impact of water hammer can be significantly mitigated or eliminated at well design stage or by adjusting the

operating parameter(s).

IntroductionThe importance of water injectors has increased as waterflooding is entrenched as the most popular secondary recovery

process in matured reservoirs. However, inappropriate shut-in operation and well design of water injectors frequently causes

water hammer, resulting in severe damage by sand production, detrimental accident by tubing or valve rupture, and

premature abandonment by wellbore collapse. Water hammer effect is a well known phenomenon that can occur at thepipeline where water is being transported. A transient nature of pressure wave occurs when water in motion is forced to stop

or change its direction suddenly. Two different mechanisms can explain the causes of water hammer downstream and

upstream of the shut-in valve. Upstream of the valve, when the valve is rapidly closed, the mass of water (that is movingforward) builds up to a high pressure and shock wave at the position of the valve and the pressure wave travels back and forth

until the energy dissipates due to friction. On the other hand, downstream of the valve, the mass of water tends to continueflowing by law of inertia, when the valve is instantly closed. It creates a temporary vacuum just below the shut-in valve,

pulling the water body back to hit the shut-in valve and then rebound again. It is a cyclic process that gradually dissipates

due to friction. Water hammer intensity is at the peak at the shut-in valve and it tends to fade away farther from the valve

because the pressure wave loses its energy during propagation due to friction.

The study of water hammer was first initiated in the nineteenth century and many researchers have put forth considerable

effort to understand the principle of water hammer and develop appropriate expressions1-9. A big milestone was made byJoukowsy4. He developed a well known analytical equation called fundamental equation of water hammer, which is still in

popular use. The Joukowsys equation is: