Mechanics of light weight proppants: A discrete approach

Abstract

Proppants are a specific application of granular materials used in oil/gas well stimulation. Employment of hard and soft particle mixtures is one of the many approaches availed by the industry to improve fracture resistance and the stability of the granular pack in the hydraulic fracture. Current industrial practices of proppant characterization involve long term and expensive conductivity tests. However, the mechanics governing the proppant pack response, in particular the effects due to material, shape and size of particles on the pack porosity, stiffness and particle fragmentation are not understood clearly.The present research embodies analytical and experimental approach to model hard (ceramic) and soft (walnut shell and/or pure aluminum) proppant mixtures by taking into account polydispersity in size, shape and material type of individual particles.The hydraulic fracture condition is represented through confined compression and flowback loads. The particle interactions clearly illustrate changes in pore space as a function of pressure, mixture composition and friction. Single particle compression tests on individual particles are carried out to obtain mechanical properties which are incorporated into the finite element models and are further correlated with the compression/crush response of the mixture. The proppant pack stiffness and particle fragmentation depends strongly on the mixture composition as illustrated in the models and experiments. The flowback models demonstrated that the formation of a stable arch is essential to pack stability. Additional variables that enhance flowback resistance are identified as; addition of softer particles to a pack, softer rock surfaces and higher interparticle friction. The computational studies also led to the discovery of better, and more iv efficient pack compositions such as -short and thin pure Al needles/ceramic and the pistachio shells/ceramic mixtures. These analytical results have generated great interest and are engaged in the design of experiments to formulate future proppant pack mixtures at Baker Hughes Pressure Pumping, Tomball, TX. v

Optimizing the Lightweight Ceramic Proppants Properties

“…The range of sintering temperature for the proppants with a proposed content are relevant for a more effective industrial process of their production. The measurements proved correlation between the light ceramic proppants sintering and high sphericity coefficient and bulk density below 2 g/cm 3 . Lower density of propping agents is relevant for financial expenditures during shale gas production.…”

“…The light ceramic proppants characterized by a spherical shape are classified as a natural or synthetic propping agent with a chemical neutrality and a bulk density value below 2 g/cm 3 having a fundamental impact on a hydraulic fracturing process [1][2][3][4]. With decreasing density of proppant -approximate to density of a fracturing fluid, pumping proppants into the borehole proceeds easier [5,6].…”

Investigation of the Basic Properties of Ceramic Proppants in Raw State Obtained by the Method of Mechanical Granulation

“…Roundness and sphericity of proppants * corresponding author; e-mail: d.zarzycka@inmat.pw.edu.pl has a direct influence on the arrangement of the material in rock crevices and affects the efficiency of extraction of hydrocarbons [5]. The more grain size is less varied and are spherical, the more optimum is the positioning in the gap and better gas flow [5]. Gravity is very important because of the need to suspend the proppants in hydraulic fracturing fluid.…”

“…Homogeneity of the particles is important, as the obtained medium (gas, liquid) flows more easily between particles of the same size [10]. Roundness and sphericity of proppants * corresponding author; e-mail: d.zarzycka@inmat.pw.edu.pl has a direct influence on the arrangement of the material in rock crevices and affects the efficiency of extraction of hydrocarbons [5]. The more grain size is less varied and are spherical, the more optimum is the positioning in the gap and better gas flow [5].…”

“…After completion of the fracturing process and the ceasing of pumping the fracturing fluid into the wellbore, remaining in the deposit is solely proppant. Its quality and distribution [5] determines the efficiency of the flow of a resource [4,6]. Therefore, the choice of material for filling the role of the particular physical and mechanical proppant requires properties of: a suitable specific gravity, high crush strength, a suitable particle size, uniformity, sphericity and smoothness [7].…”