Page 182 - Reservoir Formation Damage

Chapter 9

Crystal Growth and

Scale Formation in
Porous Media*

Summary

In this chapter, the inorganic and organic precipitation/dissolution
phenomena, and their effect on the size of the suspended particles and
porosity variation are discussed and formulated.

Introduction

Civan (1996) describes that:
Injection of fluids and chemicals for improved recovery, and libera-
tion of dissolved gases, such as CO 2 and light hydrocarbons from
the reservoir fluids approaching the wellbore during produc-
tion, and variation of fluid saturations can alter the temperature,
pressure, and composition of the fluids in the near wellbore region
and tubing. Consequently, the thermodynamic and chemical balance
may change in favor of precipitate separation, aggregation of preci-
pitates, crystal growth, and scale formation. Precipitates cause
formation damage by changing the wettability and permeability of
petroleum bearing rock and cause scale formation and clogging in
tubing and pore throats.

Inorganic Precipitation

Typical inorganic precipitates include anhydrate (CaCO 3), gypsum
]
(CaSO 4'2H 2O), hemihydrate (CaSO4' / 2H 2O\ barite (BaSO 4), celestite
* Parts reprinted by permission of the Society of Petroleum Engineers from Civan, ©1996
SPE, SPE 31101 paper.

164