Enhancing stimulation treatments in carbonate reservoirs is a continuous process that includes input from previous operations and production results. Individually, stimulation provides an opportunity to improve the treatment design by means of various factors, such as changes to rates and volumes, new fluid designs, use of nitrogen to increase energy and recover additional fluid after the operation, changes to the well completion, novel diversion techniques, and additional additives. These factors affect overall optimization of fluid distribution. This paper discusses the use of particulate diverter systems during acidizing treatments and highlights how such treatments have progressed. A case study of a carbonate formation in northern Mexico is also presented.
A carbonate field in northern Mexico was analyzed in 2010 to implement a stimulation treatment. The operations ranged initially from reactive and nonreactive stimulation treatments at low-pumping rates to hydraulic acid fracturing in a single formation. After understanding the use of hydraulic acid fracturing in a single zone, multiple formation zones were fractured to improve production while introducing changes in the well completion to enable a faster operation. Multiple acid fracturing treatments during a single intervention were performed with a particulate diversion material to increase the zonal coverage. The successful diversion application has been documented using diagnostics, such as temperature profiles and radioactive tracers.
When a reactive and nonreactive stimulation treatment was performed, the average production in the field was 30 BOPD. Later, with the implementation of hydraulic acid fracturing in a single interval (more than 20 fracturing operations), the average production per well increased to 100 BOPD. More recently, in the last 15 wells, the application of fracturing improvements and the stimulation of two to three zones using particulate diversion to distribute the fluid achieved average production results of approximately 300 BOPD. These results represent a threefold increase since the initial fracturing operations and a tenfold increase since stimulation operations began in the field.
Improvements in acid diversion techniques using particulate diverters has provided significant advantages by enabling effective treatment of several zones in one step, without stopping the operation. This paper describes the design and implementation of the diverting system used during the case study to improve production in a carbonate formation.