Diversion and Keys to Stimulation Success or Failure

Abstract

The ultimate goal of diversion applications is to enhance contact of the stimulation fluid with the reservoir rock in such a way to maximize the conductive reservoir volume. Unfortunately, intentions to simplify diversions with rule of thumbs, trial and error, and pump and hope have generated uncertainties and slowed the impact in stimulation efficiency and production enhancement that this technique is capable of generating.

Fluids introduced into a reservoir for stimulation typically take the path of least resistance and therefore frequently go into areas where there are open flow paths. In many cases, those existing flow paths are neither the areas you would want to stimulate for increased production, nor areas from which formation damage will need to be removed. The success of a hydraulic fracturing or acidizing operation depends on maximizing the contact between the stimulation fluid and the intact rocks. To achieve this goal, existing fluid paths must be efficiently plugged to divert the fluid towards intact or understimulated rock for efficient application, which in turn maximizes the BOE (barrels of oil equivalent) returned from the stimulation treatment relative to unit cost.

Although industry has been deploying this technology on a more widespread basis recently, they have not been as focused on the underlying mechanisms, physics and controlling parameters which ultimately govern the success of the stimulation event.

This paper will present a comprehensive discussion around missing factors associated with jamming and plugging efficiency, particle size, particle shape, frictional parameters, particle concentration, opening geometry, rate during placement, and particles ratio. It will clearly highlight the importance of understanding the physics and mechanisms associated with a complex diversion process requiring a rigorously engineered approach.

Multiple experiments were reviewed to quantify and understand the effect and importance of the different key factors that dictate the overall goal of a successful diversion treatment. In fact, an analytical model has been developed, verified with advanced numerical simulations and calibrated with experimental results to optimize the operational parameters required for efficient diverter displacement; including adjusting the displacement rate during diverter injection and also determining and adding the required volume of spacer to minimize particle dispersion, which ensures that the diverter pill arrives at the required site intact and as designed. The proposed numerical and analytical engines are presented within the design engineering process to better enable and achieve the necessary pressure buildup required for efficient fluid diversion.