Dominant Role of Fluid Flux on Sanding

Abstract The paper is about why and how to transition to the fluid-flux based parameters from the conventional drawdown based parameters in optimizing sandface completion design and production in wells without an active sand control from the sanding risk viewpoint. Two field cases involving a high local fluid-flux induced casing failure and insensitivity of sanding severity to drawdown respectively in cased and perforated wells are presented to illustrate the dominant role of fluid flux for sanding. Then the fluid velocity at the perforation entry hole location within the commonly encountered fluid flux ranges in fields is compared to the wind speed of tropical storms and hurricanes to provide an intuitive appreciation of the fluid flux impact. The corresponding viscous drag, which is a function of rock aggregate size and fluid velocity, is calculated and compared to pressure drag, which is a function of drawdown. The former generally is orders of magnitude higher than the latter within the average size of individual grains of reservoir formations. Therefore, the calculations confirm the dominance of fluid flux over drawdown as sanding at scale is the outcome of fluid drag (the sum of pressure drag and viscous drag) overcoming rock aggregates’ frictional resistance. Thereafter, a fluid-flux based approach to sanding risk assessment and management is summarized to transition to the fluid-flux based parameters from the widely used drawdown based ones. It has two essential components: how to establish sanding severity vs. fluid flux relations and how to identify downhole conditions and their dynamic changes. In addition to empirical relations built upon field observations and rooted in sanding mechanisms, a finite element numerical model used to quantify sanding severity is described. The model consistently considers effects of reservoir pressure depletion, drawdown, rock disaggregation and fluid flux. As well specific sanding responses are dictated by well's downhole conditions and their dynamic changes, a data integration procedure within the framework of sanding fundamentals is described to get them identified or range bounded for the practical purpose of taking the right course of action. Also, a numerical strategy is illustrated to estimate well specific sanding in a timely manner to help address "what if" questions in the sanding related decision making process. The fluid-flux based approach directs completion and production engineers to focus on critical aspects and leads to a safer and more consistent operation and better business outcomes. These benefits include reserve access increase through enhancing technical and economic viability of simpler and cheaper sandface completions in developing marginal sand-prone fields; cost reduction through simplifying well sandface completions and eliminating / optimizing sanding-related interventions; heightened assurance for well reliability and longevity to protect base production; and incremental production add. The last benefit is illustrated through a well in a low-moderate oil flux regime.