Experimental Study on the Adverse Effect of Gel Fracturing Fluid on Gas Sorption Behavior for Illinois Coal

Abstract

Hydraulic fracturing is an effective technology for coal reservoir stimulation. After fracturing operation and flowback, a fraction of fracturing fluid will be essentially remained in the formation which ultimately damages the flowability of the formation. In this study, we quantify the gel-based fracturing fluid induced damages on gas sorption for Illinois coal in US. We conducted the high-pressure methane and CO2 sorption experiments to investigate the sorption damage due to the gel residue. The infrared spectroscopy tests were used to analyze the evolution of the functional group of the coal during fracturing fluid treatment. The results show that no significant chemical alteration of coal due to the fracturing fluid injection, and the damage of sorption is attributed to the physical blockage and interactions. As the concentration of fracturing fluid increases, the density of residues on the coal surface increases and the adhesion film becomes progressively denser. The adhesion film on coal can apparently reduce the number of adsorption sites for gas and lead to a decrease of gas sorption capacity. In addition, the gel residue can decrease the interconnectivity of pore structure of coal which can also limit the sorption capacity by isolating the gas from the potential sorption sites. For the low concentration of fracturing fluid, the Langmuir volume was reduced to less than one-half of that of raw coal. After the fracturing fluid invades, the desorption hysteresis of methane and CO2 in coal was found to be amplified. The impact on the methane desorption hysteresis is significantly higher than CO2 does. The reason for the increasing of hysteresis may be that the adsorption swelling caused by the residue adhered on the pore edge, or the pore blockage caused by the residue invasion under high gas pressure. The results of this study quantitatively confirm the fracturing fluid induced gas sorption damage on coal and provide a baseline assessment for coal fracturing fluid formulation and technology.

Study on Gas Adsorption–Desorption and Diffusion Behaviour in Coal Pores Modified by Nano Fracturing Fluid

“…Huang Qiming used 13 C NMR experiments and combined them with ACD Labs software to optimize the construction of the molecular structure model of a coal sample from the Illinois Basin, USA. This coal sample belongs to the high-rank coal, and we compared the waveform diagram of the mapped coal sample with the waveform diagram obtained from the actual NMR experiments, both of which are in good agreement, and concluded that the mapped coal molecular structure is consistent with the structure of coal in the real coal seam . In this paper, the molecular structure of Illinois Basin coal constructed by Huang Qiming was used for molecular simulation studies.…”

Study on Expansion Characteristics and Expansion Potential of Gypsum Rock

“…In recent years, with the further study of expansive rock and soil from macro to micro, the specific surface area has been more focused [49,[58][59][60][61][62][63][64][65][66], which can reflect the expansion characteristics and expansion potential of expansive rock and soil. At present, there are many studies on the specific surface area of expansive soil [49,58,59,63,67,68], while there are few studies on expansive rocks [60], especially the specific surface area of the first type of expansive rocks.…”

Prediction of methane adsorption capacity in different rank coal at low temperature by the Polanyi‐based isotherm model

“…The isothermal adsorption experiments targeted at the organic‐rich coal from different formations are commonly used to investigate the methane adsorption behavior on coal, which reveals the influences of various factors on the methane adsorption capacity, including gas pressure, 8,9 temperature, 10 moisture, 11,12 organic matter, 13 clay minerals, 8 pore structure, 14,15 and fracturing fluid, 16,17 and so forth. The pressure and temperature of CBM reservoirs are both increased with the increased depth.…”

“…Thus, it is significant to understand the adsorption characteristics of methane on coal not only for CBM resource evaluation and productivity prediction but also for evaluating the potential severity of gas disasters in new mines or in unmined areas of existing mines. 7 The isothermal adsorption experiments targeted at the organic-rich coal from different formations are commonly used to investigate the methane adsorption behavior on coal, which reveals the influences of various factors on the methane adsorption capacity, including gas pressure, 8,9 temperature, 10 moisture, 11,12 organic matter, 13 clay minerals, 8 pore structure, 14,15 and fracturing fluid, 16,17 and so forth. The pressure and temperature of CBM reservoirs are both increased with the increased depth.…”