Chemical Aspects of Iron Colloid Plugging in Quartz Sands and Plugging in Quartz Sands and Implications for Formation Damage

Summary

A research direction having great potential for better understanding of formation damage is the influence of colloid plugging on fluid flow behavior in porous media. Using flow through experimental equipment, we have explored the dependence of the degree of ferric oxyhydroxide colloid plugging of quartz sand packs on the solution pH and anion type at a constant temperature of 208-F [97.7 deg C). At a pH of 5, permeability reductions were greatest in the order PO 3/4-, SO 2/4-, and C1 This order was reversed at a pH of 9. The results suggest that plugging occurs by two fundamentally different plugging occurs by two fundamentally different mechanisms. First, flocculation/coagulation of the ferric hydroxide leads to formation of filter cake in the low-ph case. Second, colloid/quartz surface interaction produces a more uniform accumulation of colloid produces a more uniform accumulation of colloid throughout the core at higher pH's.

Introduction

Recently the phenomenon of colloid fouling or colloid plugging has become more widely recognized as a plugging has become more widely recognized as a potential problem for oilfield production, especially in potential problem for oilfield production, especially in waterflooding and in enhanced oil recovery (EOR). Colloids are defined as particles in the 0.1 - to 200-Am size range. Concern about this problem has led to strict control over injection fluid chemistry, particularly in regard to hydrolyzable metal ions such as Fe3+, Al3+, and Mn2+5+4+. A similar concern exists about controlling the fluid chemistry of reinjection fluids from geothermal wells. Even if the fluid chemistry is well controlled, the corrosion of casing or the existence and formation of colloidal material within the reservoir from the dissolution/oxidation of minerals, such as siderite, pyrite, and chlorite, are potential problems. In addition, pyrite, and chlorite, are potential problems. In addition, EOR operations, such as alkaline flooding and steam-flooding, can lead to a strong increase in dissolved silica concentrations and the formation of colloidal silica. Also, the very fine-grained nature of many clays makes their surface chemical behavior identical to amorphous colloids. Clay migration is a well-known but not well-understood phenomenon, although considerable progress has been made by several groups in modeling progress has been made by several groups in modeling the clay release and plugging process.

If the interaction of colloids with reservoir rock is understood, the occurrence of plugging problems may be predicted and a more quantitative model for clay predicted and a more quantitative model for clay migration and plugging can be developed. In addition to preventing plugging, selective colloid fouling might be preventing plugging, selective colloid fouling might be used as a mobility buffer in reservoirs with a heterogeneous permeability distribution. The purpose of this paper is to discuss some of the chemical aspects of colloid plugging, particularly ferric iron colloids, and to discuss some experimental studies of Fe 3 + colloid plugging behavior in quartz sands. Furthermore, application plugging behavior in quartz sands. Furthermore, application of these results to reservoir systems is discussed.

Review

Three major processes are involved in colloid plugging:

  • (1)

    generation of colloids,

  • (2)

    transport of suspended particles, and

  • (3)

    attachment of particles. Generation of particles, and

  • (3)

    attachment of particles.

Generation of colloids, particularly those of interest in formation damage, such as ferric iron and aluminum hydroxide and silica colloids, can result from a number of processes. Corrosion and/or oxidation of steel casing and pumps are responsible for much of the iron colloids. Silica and aluminum colloids typically result from high levels of supersaturation in the solution phase produced during perturbations of the reservoir through injection of caustic perturbations of the reservoir through injection of caustic or steam. This paper, however, will deal primarily with the transport and attachment of ferric colloids.

Transport is a physical hydraulic process that is dependent on parameters such as flow rate, grain size and shape, and viscosity. Attachment is a chemical process and is dependent on both chemical and physical parameters of the system. Fortunately, a great deal of parameters of the system. Fortunately, a great deal of work has been done in the area of particle migration because of the importance of colloid filtration in water quality engineering. The majority of this research has been conducted on particle filtration at room temperature in aqueous fluids. We present a short summary of the previous research on transport and attachment processes. previous research on transport and attachment processes. Transport/Collection. During the last 10 years, a number of transport models have been proposed to explain the behavior of suspended particles during filtration using porous media. These models are based on theories developed for aerosol filtration.

JPT

P. 1682

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