Investigation of Carbon Dioxide Foam Performance Utilizing Different Additives for Fracturing Unconventional Shales

Abstract

The application of CO2 foam has caught overwhelming attention for fracturing shales. In applications, high foam deterioration and insufficient viscosity at operating conditions are the major concerns associated with foam fracturing process. In this study, polymer-free CO2 foam possessing high stability has been presented through chemical screening and optimization under HPHT conditions. Initial screening was performed by conducting a series of foam stability experiments considering different commercial anionic surfactants, concentration, and foam stabilizer addition using FoamScan instrument. Foam rheology study was then performed by considering the similar investigated factors under fracturing conditions using HTHP foam rheometer. All the tested solutions were prepared in fixed brine salinity and HPAM polymers with different molecular weights were used in evaluation of the performance of the designed polymer-free foam in term of foam strength. In comparison with other types of surfactant, alpha olefin sulfonate (AOS) exhibited the best foam stability and viscosity at testing conditions. The optimum AOS concentration providing the best performance was found to be 5000 ppm and its combination with 5000 ppm of foam booster (betaine) further increased AOS foam longevity. An improved result on foam stability and viscosity was not obtained by increasing surfactant concentration. Results on foam rheology reveals that CO2 foam generated in the presence of different molecular weight classical HPAM polymers could not provide significant increment in foam viscosity under experimental conditions. It was observed that these types of polymer underwent degradation due to some unfavorable mechanisms which will be expected to negatively affect its performance during fracturing process. On the other hand, polymer-free CO2 foam was found to produce a higher stability and relatively equally high viscosity compared to polymer-stabilied CO2 foam without experiencing degradation at high pressure and temperature conditions. Therefore, based on this study, it is recommended to use polymer-free foam for fracturing shales application. The use of formulated polymer-free CO2 foam which has high stability and viscosity will lead to improved fracture cleanup, minimized formation damage and pore plugging, and efficient proppant placement which will ultimately enhance gas recovery from unconventional shales.

An Experiment and Molecular Dynamics Simulation of Synergistic Foaming between a Surfactant and CO2 and the Structure–Activity Effect

“…The surfactants utilized in the experiments were commercially available and widely employed in the industry. The materials consisted of Sodium alpha-olefin sulfonate (AOS) [15], Sodium dodecyl benzene sulfonate (SDBS) [16], Sodium alcohol ether sulfate (AES) [17], Sodium laureth sulfate (SLES) [15], N-laurylamidopropyl-N,N-dimethylbetaine (CHSB), and APG0814. All of these surfactants were procured from China National Pharmaceutical Group Chemical Reagent Co., Ltd. (Shanghai, China).…”

Data-driven prediction of in situ CO2 foam strength for enhanced oil recovery and carbon sequestration

“…Experimental data on the CO 2 apparent foam viscosity under the flow loop were selected from various sources, 38–42 creating a dataset containing 157 examples. In all experiments, a mixture of alpha olefin sulfonate (AOS) surfactant and cocamidopropyl betaine was used.…”

Highly Stable Polymer-Enhanced Pickering Foams for Hydraulic Fracturing Applications

“…Hydraulic fracturing is one of the most effective and well-proven techniques for stimulating reservoirs, which involves the high-pressure injection of “fracking fluid”, typically a water–sand slurry, into the deep-rock formations to create and enlarge cracks that provide pathways for shale gas and oil recovery. − However, such a substantial water injection inevitably results in a number of issues, such as high water consumption, low flowback efficiency, potential groundwater contamination, and possible reservoir damage, especially for the water-sensitive formations. − In this regard, foamed fluids have been utilized as an alternative to water-based fracking fluids, as they consume less water while achieving favorable fracking performance, and their high viscosity guarantees a good proppant-carrying capacity with less chemical addition. , In spite of this, the use of foam-based fluids as fracking fluids is still restricted, primarily due to their thermodynamic instability, especially under a high-temperature reservoir condition. Indeed, the foam is a typical two-phase fluid and tends to readily degrade into water and gas through liquid drainage, bubble coarsening, and coalescence, , and the increased temperature would quicken these phenomena resulting from the reduced viscosity of the liquid phase .…”