Numerical study of supercritical CO₂ and proppant transport in different geometrical fractures

Abstract

Supercritical CO2 (SC‐CO2) fracturing, as a kind of waterless fracturing method, is an effective treatment in the unconventional oil and gas industry. Due to its characteristic lower viscosity, supercritical CO2 fracturing is likely to create thin and long fractures that connect pre‐existing natural fractures and generate complex fractures. It is therefore very challenging to predict how far supercritical CO2 carrying proppant can go and how proppant will be transported in natural fractures, when natural fractures are contacted or penetrated by induced fractures. In this paper, proppant transport with supercritical CO2 in fractures was analyzed using the computational fluid dynamics method. Three types of fractures – planar fractures, T‐shape fractures and crossing‐shape fractures – were modeled. Five parametrical cases were studied using the T‐shape and crossing‐shape models. Results show that, for T‐shape fracture cases, a turbulent flow regime might develop at a fracture junction, which can make proppant propagate to natural fractures. For crossing‐shape fractures, a turbulent flow takes place behind the fracture junction, which causes a little sand dune to form downstream of the induced fracture. With the reduction in the width of the natural fracture, the height of the sand bank at the thinner natural fracture is higher than that at the wider natural fracture. Using a proppant whose density and diameter are respectively less than 1540 kg/m3 and 0.25 mm, as well as a sand‐carrying fluid whose sand ratio ranges from 8% to 10% and injection rate exceeds 2 kg/s, is beneficial to prop natural fractures. Moreover, the larger the intersection angle of the crossing‐shape fracture is, the more difficult it is for proppant to enter natural fractures. This study reveals the influence of fracture geometry on proppant transport with SC‐CO2. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

Review of fundamental studies of CO2 fracturing: Fracture propagation, propping and permeating

“…Proppant transport in Sc-CO 2 follows a similar rule to that for the mobilization of proppant in slickwater (Wang et al 2018, Huo et al 2017. Particle movement (Fig.…”

Numerical Study on Proppant Transport in Supercritical Carbon Dioxide under Different Fracture Shapes: Flat, Wedge-Shaped, and Bifurcated

“…Since the factors such as proppant radius, density, and flow rate have been deeply studied by scholars, − these parameters will not be analyzed in this paper. Different from conventional slickwater, supercritical carbon dioxide is extremely sensitive to pressure and temperature.…”

“…Song et al 33 used the mixture model in the Euler−Eulerian method to study the properties of supercritical carbon dioxide fluid transport proppant but did not perform temperature and pressure sensitivity analysis. Wang et al 34 studied plane fractures, T-shape fractures, and Xshape fractures but ignored the influence of the bypass angle and wedge fractures. Zheng et al 14 studied the effects of proppant concentration, injection temperature, and velocity on proppant migration using the CFD-DEM method, but he did not conduct in-depth studies on temperature and pressure that affect the physical parameters of supercritical carbon dioxide.…”

Wear Mechanism of Abrasive Gas Jet Erosion on a Rock and the Effect of Abrasive Hardness on It

“…When more abrasives simultaneously impact the rock surface, the cracks formed by the impact of each abrasive intersect with each other, which leads to rock damage. 6 Geofluids…”

“…Abrasive gas jets are widely used in surface treatment engineering such as in drilling and lacquer and rust removal from metals and ceramics [1][2][3]. In recent years, they have been introduced in unconventional oil and gas production [4][5][6]. In particular, the abrasive gas jet can assist in drilling coalbed methane, can avoid problems that often occur in water jet-assisted drilling such as borehole collapse, and have broad application prospects [7,8].…”