the use of sea water in well c

8/2/2019 The Use of Sea Water in Well C

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THE SPE IMAGE LIBRARY SPE 5030

The Use of Sea Water in Well Cementing

5030

Smith, R.C., SPE-AIME,

Amoco Production Co.Calvert, D.G., SPE-AIME,

Dowell

June 1975

The performance of cement slurries using sea water can be predictable

to a safe degree. Using sea water reduces placement time, increases

early strength development, and shortens waiting-on-cement time.

The effects of sea water on accelerators, retarders, fluid loss, and

dispersant additives are discussed.

Introduction

This study shows that if sea water is used in place of fresh

water for mix water in cementing systems, the setting rate

of cement is accelerated. This affects cement thickening

time, early strength development, and waiting-on-cement time.

Using sea water also affects the prehydration of bentonite

and the activity of accelerators, retarders, fluid loss, and

dispersant additives. Also, improved bonding characteristics

are indicated.

Uncontaminated waters from seven oceans under current

drilling activity are analyzed and are shown to be very

similar in composition. For preliminary laboratory testing

with cements, the composition of sea water can be approximated

by the ASTM standard sea water. Also, a complete analysis of

a specific sea water can be obtained by measuring only the

chloride content. The other major constituents can be

calculated from this chloride ion. Other investigators have

found that, for most practical purposes, the ratios of all

major components of sea water to chlorides are constant.

Cement slurries for well completions generally perform

best when mixed with fresh water. It is generally believedthat if the water is potable, it is satisfactory for cements.

This practice is followed generally on land operations, where

practical and economical, and has been the practice in

several offshore areas. However, with increased offshore

drilling activities, the use of sea water for mixing cement

slurries for down-hole cementing applications has increased

significantly. Sea water is being used as the mix water for

casing, liner, and squeeze cementing operations. Also,

because of the large loads placed on offshore platforms,

it is now the practice in many cases to grout the piles to

the jacket structures for effective load transfer. Some of

these grouts are mixed with sea water. The reasons for this


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THE SPE IMAGE LIBRARY SPE 5030

increased application of sea water become readily apparent

when the advantages of sea-water cementing are examined. The

advantages include (1) ready availability, (2) lower costs

because transportation is eliminated, and (3) reduced

fresh-water storage on offshore platforms.

Perhaps the most significant effect on cement

performance is caused by the presence of sodium chloride in

sea water. The effect of sodium chloride on physicalproperties of oilwell cements has been discussed by Ludwig

and by Slagle and Smith. These are both excellent

presentations on the effect of sodium chloride, but generally

only limited data on sea water were included, or the

concentration of the salt studied was considerably higher

than salt concentration in sea waters. Therefore, a better

definition of the effects of sodium chloride and other salts

in sea water on the various physical properties of cement

in the slurry state and the set state was required.

Sea-Water Composition

The concentration of dissolved materials in ocean water

varies with location and with seasons of the year. Sea

water is diluted by rivers, rain, or melting ice, or is

concentrated by evaporation. Sea water also contains all

types of suspended material, such as colloidal and larger

particulate minerals, insoluble organic compounds, and

living creatures.

JPT

P. 759


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the use of sea water in well c

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