Anhui Academy of Coal Science

Accurate characterization of water saturation in tight sandstone gas reservoirs is the key to reservoir evaluation and productivity prediction. In view of the limitations of the traditional Archie formula in describing the strongly heterogeneous pore structure and the insufficient consideration of the coupling effect of pore throat geometry and fractal characteristics in the existing models, this paper innovatively combines the fractal theory with the trapezoidal pore throat model to construct a new water saturation interpretation model. By introducing parameters such as fractal dimension (Df), tortuosity fractal dimension (DT) and trapezoidal factor (φi), the model systematically quantifies the control mechanism of microscopic pore throat distribution, capillary force field evolution and stress sensitivity (rock elastic modulus E = 1.05 × 103 MPa) on water saturation. The model was verified by the sealed coring and nuclear magnetic resonance experimental data of 10 groups of typical tight sandstone cores in Sulige gas field, Ordos Basin. The results show that: (1) The absolute error range between the water saturation calculated by the model and the measured value of the closed coring is 0.89–11.27%, indicating that the model has high accuracy and good applicability. (2) There is a significant negative correlation between reservoir water saturation and reservoir temperature and displacement pressure difference: for every 20 °C increase in temperature, water saturation decreases by about 4.5%; when the displacement pressure difference increases by 1 MPa, the water saturation decreases by about 6.3%. (3) The study further shows that under the condition of constant displacement pressure difference, the water saturation of the reservoir is positively correlated with the effective stress and negatively correlated with the maximum/minimum pore throat radius ratio. Rock mechanics parameters also have an impact on water saturation—the lower the elastic modulus, the higher the Poisson’s ratio, the greater the reservoir water saturation. The model can accurately predict the water saturation of the reservoir and provide an effective tool and support for the fluid quantitative evaluation and development scheme optimization of tight sandstone gas reservoirs.

BackgroundRadiotherapy resistance contributes to poor prognosis in esophageal squamous cell carcinoma (ESCC). Retinoblastoma-binding protein 7 (RBBP7) is a nuclear protein, and it can promote or inhibit tumor progression in cancer, but its function in ESCC cells and impact on radiosensitivity remains unclear.MethodsRBBP7 expression in cancer was analyzed using an online website. The expression levels of RBBP7 in ESCC cells (TE-1 and KYSE-150) and tissues were tested. Cells were subjected to RBBP7 gene silencing and irradiation (IR). Assays included CCK-8, clonogenic survival, flow cytometry (apoptosis/cell cycle), ROS detection, and Western blotting for DNA damage (γ-H2AX) and STAT3 signaling. Additionally, pathological tissue specimens and clinical data from ESCC patients were used to explore the expression of RBBP7.and its relationship with the clinical parameters of patients.ResultsRBBP7 was overexpressed in malignant tumors. In ESCC cells, the mRNA and protein of RBBP7 were also highly expressed. After silencing RBBP7 combined with IR treatment, contradictory effects were observed between cell lines: In well-differentiated TE-1 cells, RBBP7 knockdown suppressed proliferation, enhanced radiosensitivity (SER=1.370), increased ROS/DNA damage (γ-H2AX), promoted apoptosis, and reduced STAT3 activation (possibly through STAT3 signaling). In poorly-differentiated KYSE-150 cells, knockdown promoted proliferation, decreased radiosensitivity (SER=0.775), reduced apoptosis, and increased p-STAT3. In addition, knockdown caused S-phase arrest (TE-1) versus G0/G1 arrest (KYSE-150), with divergent CDK4/Cyclin D1 regulation. Clinical analysis confirmed RBBP7 positivity correlated with tumor differentiation, TNM stage, and radiotherapy method.ConclusionRBBP7 is highly expressed in ESCC, and it exerts cell context-dependent dual roles in ESCC, leading to differences in cellular radiosensitivity, possibly mediated through STAT3 signaling. This dichotomy highlights its potential as a differentiation status-specific therapeutic target.

A popular attenuation velocity model for complete waveform inversion and seismic migration, the visco-acoustic (VA) smooth velocity model has first-order or high-order partitioned continuous derivatives. To compute the gradient scattering field caused by velocity gradient changes in the acoustic smooth velocity, we provide an integral technique in the acoustic F-K domain. We conduct Taylor expansion on the disturbance term and transform the velocity disturbance term into a velocity gradient term, in contrast to the conventional F-K domain integration approach that retrieves the scattering field caused by medium disturbance. Next, we compute the gradient scattering field in the VA smooth velocity model using the phase-shift interpolation (PSPI) technique. We examine the propagation law of gradient scattering waves in VA medium using the F-K domain integration technique in combination with the Futterman model. We provide a simulation approach for velocity gradient scattering wave numbers in the VA smooth medium, based on the numerical simulation technique in the F-K domain. The numerical study’s results demonstrate that the viscosity of VA medium reduces the amplitude of seismic waves in that medium. The thicker seismic wave phase axis indicates the loss of certain high-frequency components. The amplitude of the seismic gradient scattering waves decreases in the smooth velocity model. After smoothing, the velocity gradient shift is relatively small, and the amplitude of the gradient scattering wave signal in the forward modeling of the viscous F-K domain method is greater than that in VA FD and VA Generalized Born approximation (VA GB) methods. The results of the numerical analysis have validated the effectiveness of the method.

Superplasticizers (SPs) are indispensable in modern concrete technology. A novel, cost-effective method for synthesizing a high-performance SP using coal-based humic acid (CHA) derived from lignite is presented. Through oxidative depolymerization of lignite to prepare CHA, followed by sulfomethylation and condensation reactions, a CHA-based SP (called SP(CHA)) was successfully developed. Structural characterization confirmed the successful synthesis of CHA and its transformation into SP(CHA). Notably, the CHA demonstrated superior sulfomethylation reactivity compared with a commercially available sodium humate (NaA). Performance evaluations showed that the synthesized SP(CHA) outperformed both a commercial sulfonated naphthalene–formaldehyde condensate and SP(NaA) in terms of water-reduction efficiency, slump retention, and enhanced long-term compressive strength. Specifically, SP(CHA) achieved a water-reducing rate of 16.4% and a 28-day compressive strength improvement of 23.2%, exceeding the benchmarks for high-efficiency water reducers. By harnessing abundant and low-cost lignite resources, the approach holds substantial promise for advancing sustainable construction practices.

Determining the starting time of the CO2 injection is the key factor affecting the effect of CO2 injection and CH4 production. This study uses the Panyidong mine in the Huainan mining area as an example. First, fully coupled mathematical models are established. Second, the evolution law of the reservoir parameters under different starting times of CO2 injection is visualized. Then, the starting time of the CO2 injection is determined, and the transformation process of CH4 displaced by CO2 is discussed. Finally, the connotation of the continuous fluid process during the CO2-ECBM process is analyzed, and constructive suggestions for CO2 injection are presented. The results show that during the CO2-ECBM process, the reservoir pressure and gas content greatly change near the CO2 injection well, and gradually decrease near the CH4 production well. The competitive adsorption of the gas is exothermic, and the reservoir temperature gradually increases. The competitive adsorption of gas causes matrix expansion, which results in a decrease in permeability. The CH4 production rate can be increased by about 2 times, and the evolution law of the CO2 injection rate shows little difference. If the purpose of CO2 injection is to store CO2, the start time of CO2 injection may be set as the 2000th day. The CO2-ECBM process can be divided into three stages to characterize the importance of displacement and replacement effects in each stage. Determining the starting time of CO2 injection and giving more desorption time to CH4 is conducive to the expansion of pore and fracture spaces, and then gives more competitive adsorption time to gas. This study can promote the engineering implementation of the CO2-ECBM technology.