Design of experimental system for supercritical CO₂ fracturing under confining pressure conditions

Abstract

Supercritical CO 2 has the characteristics of low viscosity, high diffusion and zero surface tension, and it is considered as a new fluid for non-polluting and non-aqueous fracturing which can be used for shale gas development. Fracturing refers to a method of utilizing the high-pressure fluid to generate fractures in the rock formation so as to improve the oil and gas flow conditions and increase the oil and gas production. In this article, a new type of experimental system for supercritical CO 2 fracturing under confining pressure conditions is designed, which is based on characteristics of supercritical CO 2 , shale reservoir and down-hole environment. The experimental system consists of three sub-systems, including supercritical CO 2 generation system, supercritical CO 2 fracturing system and data analysis system. It can be used to simulate supercritical CO 2 fracturing under geo-stress conditions, thus to study the rock initiation pressure, the formation of the rock fractures, fractured surface morphology and so on. The experimental system has successfully carried out a series of supercritical CO 2 fracturing experiments. The experimental results confirm the feasibility of the experimental system and the high efficiency of supercritical CO 2 in fracturing tight rocks. K: Overall mechanics design (support structures and materials, vibration analysis etc); Manufacturing 1Corresponding author.

Full-Sample X-ray Microcomputed Tomography Analysis of Supercritical CO2 Fracturing in Tight Sandstone: Effect of Stress on Fracture Dynamics

“…We used a laboratory fracturing system that is designed for multiple fluids (such as CO 2 and water). , The setup consists of a pump, triaxial-loading system, sample holder, constant-temperature water bath system, control/measurement system, etc. (as shown in Figure ).…”

Laboratory Investigation of Cryogenic Fracturing of HDR Wellbores Under Triaxial-Confining stresses

“…Measuring instruments can record changes in pressure and temperature over time. The minimum resolution and accuracy of temperature recording are 1 ℃ and 1% respectively, and the minimum resolution and accuracy of pressure recording are 0.1 MPa and 1% respectively [13].…”

Supercritical Carbon Dioxide Utilization for Hydraulic Fracturing of Shale Reservoir, and Geo-Storage: A Review

“…The fracturing experiments were performed to observe the stress measurement on shale specimen using Sc-CO 2 and slick water as fracturing fluid. , It was reported that Sc-CO 2 requires almost 50% lower breakdown pressure as compared to water. ,,,− The reason behind this is Sc-CO 2 shows low viscosity, low surface tension, and high diffusivity due to which it can easily penetrate in shale and significantly decreases the strength of shale rock by an amount equal to the increase in pore pressure. , But the time required for fracturing shale using Sc-CO 2 was 20 times more under same experimental condition due to CO 2 compressibility. ,, Moreover, the fracturing fluid is continuously injected, the loading rate of Sc-CO 2 pressure gradually increases, while the loading rate of water pressure rises rapidly until the fracturing process reaches its maximum value. ,,, There are various parameters that influence the breakdown pressure of the shale specimen while using Sc-CO 2 and water as fracturing fluid as discussed in Figure :…”

“…As shown in (Table ) a number of researchers have conducted a comparative analysis of water and supercritical carbon dioxide (Sc-CO 2 ) to examine how they affect the fracture characteristics of shale . The findings from their studies indicate that Sc-CO 2 creates a larger number of branches around the main fracture, resulting in slightly curved and deviated fractures, whereas water tends to produce straight or slightly straight fractures. ,,,, This disparity can be attributed to the significant expansion of Sc-CO 2 , which is facilitated by its unique properties of low viscosity and high diffusivity. These properties enable Sc-CO 2 to easily penetrate the small pores of shale specimens and generate multiple complex fractures …”

“…Currently, there is a need for the development of specialized surface and downhole tools to accommodate the unique characteristics of Sc-CO 2 in the fracturing process. The number of the design have been proposed for fracturing operation by using Sc-CO 2 fracturing fluid. , Interaction between shale, brine and Sc-CO 2 and CO 2 geostorage: The properties of shale are noticeably affected by the physical and chemical interactions between CO 2 and shale, as well as CO 2 and water/brine in shale . The long-term impact of these interactions on CO 2 geostorage and shale gas recovery is still not fully understood by researchers.…”