In stimulation and injection treatments for removing or preventing formation damage, placement of the injected fluids is essential. Throughout the years, several diversion and placement techniques have been applied to obtain a desired fluid placement. A recent development is the application of distributed temperature sensing (DTS) to monitor the temperature profiles along the wellbore in real time during these treatments. Recent case histories showed that fluid placement can be quantified. Quantification of fluid distribution enables one to determine the flow distribution both before and after a diverter stage so that the diversion effect can be quantified.
This paper discusses several case histories where DTS was applied to quantify the effectiveness of different diverters. The effects of chemical diverters, such as relative permeability modifiers (RPM) and in-situ crosslinked acids (ICAs), and more traditional diverters, such as rock salt, are discussed. Because of the advanced monitoring used with the temperature profiles, both the immediate and the sustained effect of the diverters can be measured. The changes in the flow distribution are not limited to diverters. Reactive fluid or changes in flow rate can change the flow distribution as well. These effects were measured during the stimulation treatments.
The post-treatment analysis of the measured temperature profiles in combination with treatment pressures and flow rate information resulted in accurate knowledge of the effectiveness of the different diverters and stimulation effects over time. This knowledge will be used in future treatments to help optimize volumes, rates, fluid systems, and the selection of the appropriate diverter.
Effective fluid placement and full zonal coverage has been a challenge to the industry. The applications where fluid placement and zonal coverage is important include but are not limited to:
Scale-inhibitor squeeze treatments
Water injection for enhanced recovery
Injection of sand-consolidation materials
This paper focuses on matrix-acidizing treatments, but several of the techniques discussed can also be applied to some of the other applications. During matrix-acidizing treatments, the goal is to remove or bypass damage in the near-wellbore area. Throughout the long history of acidizing, several fluid-diversion and placement techniques have been applied to ensure this goal is achieved over the entire zone of interest. Without effective fluid diversion, the injected fluids will follow the path of least resistance and will only stimulate the zones with the highest permeability, lowest reservoir pressure, or the least damage.