Computation of local permeability in granular soils using spatial time domain reflectometer

This letter proposes semi-analytical methods to obtain the local permeability for granular soils based on indirect measurements of the local porosity profile in a large coaxial cell permeameter using spatial time domain reflectometry. The porosity profile is used to obtain the local permeability using the modified Kozeny-Carman and Katz-Thompson equations, which incorporated an effective particle diameter that accounted for particle migration within the permeameter. The profiles of the local permeability obtained from the proposed methods are compared with experimentally obtained permeability distributions using pressure measurements and flow rate. The permeabilities obtained with the proposed methods are comparable with the experimentally obtained permeabilities and are within one order of magnitude deviation, which is an acceptable range for practical applications.

Internal Instability in Soils: A Critical Review of the Fundamentals and Ramifications

Seepage-induced fine-particle migration that leads to a change in the conductivity of a soil matrix is referred to as internal instability. This could jeopardize the structural integrity of the soil matrix by initiating suffusion (or suffosion), a form of internal erosion. Susceptibility to suffusion has been studied mostly under extreme laboratory conditions to develop empirical design criteria, which are typically based on the particle size distribution. The physics governing the process have not been comprehensively uncovered in the classical studies because of experimental limitations. Mainstream evaluation methods often over-idealize the suffusion process, holding a probabilistic perspective for estimating constriction sizes and fines migration. Prospective studies on constitutive modeling techniques and modern computational techniques have allowed a more representative evaluation and deeper insight into the problem. Recent advances in sensing technologies, visualization, and tracking techniques have equally enriched the quality of the data on suffusion. This paper sets out to present the long-standing knowledge on the internal instability phenomenon in soils. An attempt is made to pinpoint ambiguities and underscore research gaps. The classical empirical studies and modern visualizing techniques are integrated with particle-based numerical simulations to strengthen the theoretical understanding of the phenomenon.

Study on Particle-Size Process on Internal Erosion of Grap-Graded Soil--Rock Mixtures of Different Fine Contents

Soil–rock mixtures are widely encountered in geotechnical engineering projects. The instability and failure mechanism of grap-graded soil–rock mixtures under rainfall conditions has always been the focus of geological disaster research. To deeply explore the mechanism of seepage deformation of soil–rock mixtures, an indoor physical permeability test that considers soil–rock mixtures with different fine contents was conducted, and a particle-scale numerical simulation test of the permeability evolution was carried out using the coupling model of PFC3D and ABAQUS. The test results showed that the spatial distribution of fine particle loss along the height direction could be divided into three areas: top loss, middle uniform, and bottom loss area. The “island” effect of coarse particles, which is caused by excessive fine content and makes the fine particles bear more load, was eliminated with the loss of fine particles. In this preset working condition of coarse and fine particle diameters, setting FC to 35% may be the best way to fill the voids between the coarse particles. Particle migration leads to a change in the load-bearing skeleton structure, thereby causing seepage deformation. Therefore, the particle-scale numerical test method can better reproduce the seepage deformation process of grap-graded soil–rock mixtures.

A comprehensive research in chemical consolidator/stabilizer agents on sand production control

Sand or fine is a typical product in many processing of oil production from unconsolidated and weakly consolidated formations. High variation of in situ stress, fluid production rate above maximum sand-free rate, and water production are main primary sources of the sand production. Sand production can cause hazardous operational problems to the facilities, pipes, and wellbore. Hence, it is a significant problem that requires to be managed and studied. To minimize the operational impacts of particle migration, chemical consolidators/stabilizers can be utilized to alter surface properties of sand and formation particles. The decreasing zeta potential besides increasing the cohesion between sand and formation particles could result in controlled sand production. However, understanding the mechanism and application of chemical methods to alleviate sand production is not well-discussed. This study presents and discusses chemical consolidator/stabilizer agents, which may be applied for managing sand production in the petroleum industry. This was achieved through a comprehension review of the literature and the application of chemical consolidators/stabilizers in other fields such as bauxite residue (red mud and red sand) control, desert sand, mine reclamation, wind erosion control, unpaved road modification, and enhancement of water retention and soil infiltration properties that are similar to formation sand. Standard experimental methods in various fields, for performance analysis of chemical consolidator/stabilizer agents, are compared and summarized. The consolidation/stabilization mechanisms of various types of chemical consolidator/stabilizer agents are discussed and compared. This review potentially can be used to inhibit blind usage of chemicals and functions as a reference to additional research in sand production control in petroleum engineering. The results are appropriate for extending quantitative approaches for performance evaluation of sand consolidator/stabilizer agents.