Abstract

Formation damage due to fines migration is a major factor which reduces reservoir productivity. It is, therefore, essential to know the critical condition at which particles migrate in pores and subsequently plug the channels. This paper describes the application of fractal analysis for predicting critical conditions for particles to deposit in pores. The experimental data were obtained by injecting suspensions (bentonite) through a fabricated glass micro capillary (100 µm ID) at a controlled flow rate and at the same time continuously monitoring the pressure build-up across the capillary. Based on the experimental data and theoretical analysis, a criterion for predicting the critical condition for fines migration in pores is proposed.

Introduction

Petroleum reservoirs contain particles of loose solid materials in pores. These particles are free to migrate through the pores along with the fluids that flow in the reservoir. During migration, these fines are not carried all the way through the formation by the fluids, instead, they concentrate at pore restrictions. If certain conditions are met, these particles bridge pore restrictions leading to pore plugging and reduction in permeability. Numerous experimental studies have been conducted on core plugs to understand the factors which control the migration of fines in porous media (1–6). However, the provision of a satisfactory model to predict particle deposition in porous media is still a problem due to the complexity of the process. Most of the widely used deposition models available in the literature are based on empirical relations which are limited to specific systems or processes (7–12).Payatakes et al. (13), Hung and Tien, (14), and Husein et al. (15) used two-dimensional (2D) trajectory analysis to predict the pressure drop in a single micro capillary. Paraskeva et al. (16) and Burganos et al. (17) used three-dimensional (3D) trajectory analysis of particles in uniform and constricted tubes. Husein et al (15) developed an experimental set-up and measured the pressure build-up across a fabricated micro capillary while flowing particle suspension through the capillary.

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