Experimental study of sand production and permeability enhancement of unconsolidated rocks under different stress conditions

Production of sand is a common issue in oil and gas fields causing various production problems. However, as a result of sand production, rock permeability can also be increased at near-wellbore areas, which is considered to be an advantage of solid particles production. Therefore, this study aims to investigate sand production behavior and permeability changes during sand production experimentally. To do so, a specific core flooding system capable of applying different radial and axial stresses has been designed which is equipped with a special fluid distributer at the outlet to prevent any sand particle blockage during fluid production. As part of this study, eleven unconsolidated synthetic core samples were made and used during the experiments. The flooding experiments were carried out under various radial to axial stress ratio conditions to see how the stress ratio could affect the sand production phenomenon. The experimental results showed that the mass of produced sands was strongly depended on the stress ratio such that at higher ratios, the lower amounts of sand were produced. A correlation was developed to predict the mass of sands produced as a function of the stress ratio and the volume of fluid injected. The results also revealed that the original core sample permeability values were enhanced due to sand production. As a result of this study, a new model has also been introduced to predict the permeability enhancement as a function of the cumulative mass of sand produced as well as the initial permeability of the samples which can be used by petroleum engineers for better planning of production programs.