Investigation of The Reliability of Hollow Glass Spheres as a Density Reduction Agent for Drilling Fluids under Physical Impact Forces Simulating Drilling Conditions

Abstract

Abstract The use of hollow glass spheres (HGS) is emerging as a leading solution for reducing the density of drilling fluids. With the continuous depletion of reservoirs, the presence of naturally fractured formations, and high permeability formations, the need for low-density drilling fluids is greater than ever. Gases are commonly used to bring the density of water-based drilling fluids below that of water. HGS is an incompressible alternative that has proven to be capable of eliminating deployment complications of gases while achieving satisfactory results. There is a need to examine the behavior of HGS drilling fluids overtime under downhole drilling conditions that include high temperature (HT), high pressure (HP), and, most importantly, physical impact forces associated with the attrition effect of downhole tools and equipment. The purpose of this study is to monitor the degradation and behavior of HGS drilling fluids while being subjected to conditions simulating a downhole drilling environment. A major part of the downhole environment is the physical impact forces resulting from the interaction of the drilling fluid with the circulation system components. A specially designed experiment was employed to investigate the crushing effect of the downhole drilling components on the glass spheres. As there are different pressure ratings of HGS available, the results of the experiment provide a measure of the reliability of HGS for specific operations. The experimental procedure was designed with a focus on the Wasia formation considering that its pore pressure falls in the range 51-58 lb/ft3. Therefore, the HGS fluids were subjected to HPHT degradation periods in a hot rolling oven with the addition of a destructive element to the dynamic aging cell. The degradation period duration is approximated to be similar to that typically required for drilling through Wasia. The results showed that certain ratings of HGS can degrade significantly enough for the drilling fluid to gain up to 14 lb/ft3 in density. The magnitude of this failure in HGS means that selecting the wrong rating has the potential to put the well under substantial risk. The potential drilling troubles due to this failure include significant loss of circulation, formation damage, reduction in rate of penetration (ROP), aquifer water contamination, and stuck pipe.