Using Advance Modelling Techniques to Design Diversion for Acidizing, Fracturing & Re-Fracturing

Abstract

Stimulation fluids injected into a reservoir generally take the path of least resistance, i.e., zones of high permeability where often the stimulation is not as important as other critical under-stimulated areas. This leads to under-stimulated zones, which negatively impacts the production, or over-stimulated zones, which might lead to softening of the wellbore rock and, with time, might have also a negative effect on production. The efficiency of a fracturing, acidizing, or re-fracturing treatment depends on maximizing its contact with the zone of interest and uniform distribution in the reservoir. To achieve this goal, existing fluid paths must be efficiently and temporarily blocked, therefore diverting the treatment towards under-stimulated areas, a process known as diversion. The main goal of diversion is to distribute the stimulation fluid across the reservoir uniformly.

An analytical model based on computational fluid dynamics and discrete element modelling has been developed to optimize the different parameters that affect an optimum diversion. The parameters that effect the efficiency of plugging are flow rate, PSD (Particle Size Distribution), concentration, carrier fluid, and the displacement rate during diverter injection. The modelling can be customized depending upon the type of application.

This paper will summarize an engineering workflow to optimize diversion design and present successful cases globally of biodegradable, bi-particulate diversion applications in matrix acidizing enabling a production increase of 140%, re-fracturing applications (which led to the formation of new fractures in the new zones not previously stimulated), and uniform fracture growth from horizontal wells.

We believe that an engineering approach is critical to the success of matrix acidizing, fracturing, and re-fracturing. The results demonstrate the effectiveness of advance modelling and bi-particulate diverters in minimizing the formation damage, evenly distributing the stimulation fluid, and thereby increasing its effectiveness and retarding the softening of rock, and to enhance the production across the target zone. The lessons learned from various applications of these engineered bi-particulate diverters can be applied for stimulation design and planning.