Evaluation Of Diverting Agent Effectiveness And Cleanup Characteristics Using A Dynamic Laboratory Model - High Permeability Case
Authors: King George E. , Hollingsworth Frank H. 
Published: December 2007

Abstract
The performance of a diverting agent in any workover procedure is critical to the success of the treatment. Since the factors governing diverter performance are as varied as formation permeability, performance are as varied as formation permeability, temperature, carrier fluid, and produced fluid, there is no single best diverter for all operations. This paper reports results of tests on the critical areas of diverting effectiveness, permeability damage, and removal of the diverter after the treatment.
The diverters were evaluated in a circulating test unit capable of turbulent flow past 1/4" perforations. The sand packs were designed to be perforations. The sand packs were designed to be representative of high permeability unconsolidated zones.
Even though most diverter systems have been designed to degrade or dissolve after the treatment, solvent performance was checked by flowing selected solvents in the test unit after the diverter was in place. In most cases, the solvents were capable of place. In most cases, the solvents were capable of quickly removing the diverter and restoring permeability. Data is presented on removal of permeability. Data is presented on removal of naphthalene and benzoic acid diverters by sublimation in a gas stream at 75 degrees, 100 degrees, and 150 degrees F.
Results of the evaluation indicate that the newer types of diverters such as the organic resin slurry may be more efficient diverter systems than the established diverters such as benzoic acid flakes.

Introduction
The purpose of a diverting agent in any treatment is to prevent the treating fluid from entering a water zone or a high permeability zone and divert the treating fluid to a lower permeability zone. Diverting agents are usually viscous liquids or solids dispersed in a liquid slug which cake over the permeable zones much in the same manner as a drilling mud. The diverter is usually placed in a fluid pad ahead of the treating fluid or used between stages of fluid. The effectiveness of diverters depends upon maximum temperature limits, permeability, and type of production or injection permeability, and type of production or injection (i.e., gas, oil, water).
With the increased emphasis placed on maximizing production, a need has arisen for more effective diverters which cause a minimum of formation permeability damage. A wide variety of diverting permeability damage. A wide variety of diverting agents are currently available but little comparative information exists on effectiveness vs. cleanup characteristics. The purpose of this report is to give a comparison of the more common diverting agents in a test system which has similar characteristics to diverting in a well containing high permeability matrix zones. The diverting agents will be permeability matrix zones. The diverting agents will be evaluated in terms of rate and efficiency of diverting effectiveness and degree of formation permeability damage caused by the diverter. permeability damage caused by the diverter. The diverters to be evaluated include benzoic acid flakes, naphthalene flakes, fine mesh sand, fine mesh salt, organic particulates, wax beads, hydroxypropyl guar polymer (approximately 2% residue) and organic resin. These products are among the most common diverting or fluid loss materials. The diverters will be tested at various concentrations in an attempt to formulate general recommendations for treatments in high permeability matrix situations.

RESULTS

Test Equipment
The basic test apparatus shown in Figure 1 utilizes a circulating loop of 3/8" tubing, a 6.3 gal (24 liter) reservoir and a small Moyno pump to establish flow around the loop. For the easily friable materials such as naphthalene flakes, benzoic acid flakes and wax beads, an air actuated diaphragm type pump was used to minimize crushing.
The sand pack test cells are lucite jacketed and surrounded by stainless steel cylinders with air pressure between the lucite and stainless steel to pressure between the lucite and stainless steel to ensure a positive seal.