Abstract

The fine migration and the scale formation into the porous media and the resulting production decline have long been the problem to the petroleum industry. It is also generally accepted that formation due to the particle movement and the scale formation are not thoroughly understood. In contributing to the solution of this problem, an experimentally study of calcium sulphate scale formation and the particle movement in the porous media using of packing bed with 12 different size of the glass and sand bead and the 8 core plug that gathered from the Siri oilfields. The purpose was to study the different physical and mechanical aspects of the processes leading to the formation damage caused by the movement and the entrapment of the suspended particles and the scale formation.

The permeability is the key parameter among several others that control the reservoir performance. The experiments are based on the results of the permeability reduction. The interception of the permeability reduction by the interaction between the operational parameter is very complex. Therefore, several of these factors such as the temperature, the concentration, the fluid dynamic and the type of porous media are considered.

The experimental results are analyzed and a new model which can predicts particle movement and the scaling tendency of the common oilfield water deposits in the water disposal wells, the water flooding systems, and in surface equipment's and the facilities is developed. The developed of the model is based on the experimental data and the empirical correlation, which perfectly mach the Iranian oilfields condition. This model has been applied to the investigate of the potential of the scale precipitation in the Iranian oilfields, either in the onshore or the offshore fields, where the water injection is being performed for the desalting units water disposal purpose or as the method of secondary recovery or the reservoir pressure maintenance.

Introduction

The success of oil recovery is strongly influenced by whether the reservoir permeability can be kept intact or even improved. Permeability changes in petroleum reservoirs have received a great deal of concern by the oil and gas industry. This problem is termed as "formation damage". It can occur during almost any stage of petroleum exploration and production operations. Attempting to understand formation damage is becoming an important task for reservoir engineers, oilfield chemists, and decision-makers in business, because it is first step to be taken to prevent and further alleviate this problem.

Formation Damage Mechanisms

- Two phenomena can change the permeability of the rock. One is change of porosity. This phenomenon is due to the swelling of clay minerals or deposition of solids in the pore body. The other is the plugging of pore throats. The narrow passages govern the ease of fluid flow through porous media. If they are blocked, the permeability of the porous rock will be low even though the pore space remains large. Either organic or inorganic matter may cause the plugging of pore throats. The organic induced damage is due to the formation of high viscosity hydrocarbon scale when temperature and pressure conditions in the reservoirs are changed. The inorganic damage involves release and capture of particulate including in situ fines and precipitates from chemical reactions.

The mechanisms that trigger the formation damage can be categorized into three major processes (Leone and Scott, Hydrodynamic- A mechanical force mobilizes loosely attached fine particles from the pore surface by exerting a pressure gradient during fluid flow. The movement of clay minerals, quartz, amorphous silica, feldspars, and carbonates may cause mechanical fine migration damage.

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