Constructing Ultra-Strong SERS Tags in the Cellular Raman-Silent Region by Orthogonal Array Testing Strategy.

Surface-enhanced Raman spectroscopy (SERS) tags have the advantages of unique fingerprint vibration spectrum, ultranarrow spectral line widths, and weak photobleaching effect, showing great potential for bioimaging. However, SERS imaging is still hindered for further application due to its weak spontaneous Raman scattering, biomolecular signal interference, and long acquisition times. Here, we develop a novel SERS tag of the core (Au)-shell (N-doped graphene) structure (Au@NGs) with ultrastrong and stable Raman signal (2180 cm-1) in the cellular Raman-silent region (1800-2800 cm-1) through base-promoted oxidative decarboxylation of amino acids. Exploring the factors (metal salts, amino acids, catalysts, temperature, etc.) to obtain Au@NGs with the strongest Raman signal commonly requires more than 100,000 separate experiments, while that using an orthogonal array testing strategy is reduced to 56. The existence of deep charge transfer between the Au surface and C≡N-graphene is proved by theoretical calculations, which means the ultrastrong signal of Au@NGs is the joint effect of electromagnetic and chemical enhancement. The Au@NGs have a detection sensitivity down to a single-nanoparticle level, and high-speed and high-resolution cellular imaging (4453 pixels) is obtained within 10 s by global Raman imaging. The combination of Au@NGs-based tags with ultrastrong intrinsic Raman imaging capability and global imaging technology holds great promise for high-speed Raman imaging.

[Analysis of risk factors of urethral stricture and urinary incontinence after transurethral resection of the prostate].

OBJECTIVE: The purpose of this study was to analyze the risk factors for predicting urethral stricture and urinary incontinence after transurethral resection of the prostate (TURP). METHODS: A retrospective study of 261 patients admitted from October 2018 to October 2022 who received TURP for benign prostatic hyperplasia (BPH) with complete postoperative follow-up data of at least 6 months. Patients were divided into urethral stricture group (n =18), non-urethral stricture group (n =243), urinary incontinence group (n = 12) and non-urethral incontinence group (n = 249) according to the presence of urethral stricture and urinary incontinence. Compared two groups of patient's age, course of the disease, hypertension, diabetes mellitus, IPSS score, prostate volume, maximum urine flow rate, whether preoperative urinary retention, total prostate specific antigen levels and whether preoperative status, placing a urinary catheter preoperative whether merger urinary tract infection, operative time, postoperative time, postoperative urine tube drawing time placing a urinary catheter, etc. Univariate and multivariate Logistic regression analyses were used to screen for independent predictors. RESULTS: The incidence of urethral stricture and urinary incontinence after TURP was 6.9% and 4.6%, respectively. Multivariate logistic regression analysis showed that diabetes mellitus (OR = 9.526, 95%CI: 2.824－32.127, P= 0.000); Preoperative urethral infection (OR = 6.500, 95%CI: 1.513－27.925, P = 0.012); Postoperative indwelling catheter time (OR = 2.063, 95%CI: 1.181－3.601, P = 0.011) was an independent risk factor for postoperative urethral stricture. Age (OR = 1.21, 95%CI: 1.027－1.425, P = 0.023); Diabetes mellitus (OR = 37.515, 95%CI: 2.615－538.170, P = 0.008); Postoperative indwelling catheter time (OR = 20.806, 95%CI: 3.090－140.080, P = 0.002) was an independent risk factor for postoperative urinary incontinence. CONCLUSIONS: Urethral stricture and urinary incontinence are common complications after TURP. Diabetes, preoperative urethral infection, and postoperative catheter indwelling time are independent risk factors for urethral stricture after TURP. Age, diabetes mellitus and postoperative catheter indwelling time were independent risk factors for postoperative urinary incontinence. Diabetes mellitus and postoperative catheter indwelling were common and independent risk factors for urethral stricture and urinary incontinence after TURP.

Graft patency and completeness of revascularization in minimally invasive multivessel coronary artery bypass surgery.

OBJECTIVES: Graft patency and completeness of revascularization were analyzed in patients who underwent off-pump minimally invasive coronary artery bypass grafting via a left small thoracotomy. METHODS: We retrospectively reviewed the invasive angiography findings and clinical data of 186 consecutive patients who underwent off-pump minimally invasive coronary artery bypass grafting via a left small thoracotomy. The left internal thoracic artery and saphenous vein were used to bypass two or more of three coronary artery systems: the left anterior descending artery, left circumflex artery, or right coronary artery. Before hospital discharge, invasive angiography was performed to assess graft patency. Clinical variables during hospitalization and follow-up were collected and analyzed. RESULTS: All 186 patients successfully underwent off-pump minimally invasive coronary artery bypass grafting without conversion to sternotomy or assistance of cardiopulmonary bypass. The mean graft number was 2.81 per patient (range, 2-5), and the total number of grafts was 522. The in-hospital mortality rate was 1.6% (3 of 186). A total of 181 of 186 (97.3%) patients underwent postoperative invasive angiography. Among the 510 grafts assessed by angiography, the total graft patency rate was 96.3% (491 of 510) (98.3% [171 of 174] for left internal thoracic artery grafts and 95.2% [318 of 334] for saphenous vein grafts). The rate of complete revascularization was 99.5% (185 of 186). CONCLUSIONS: Minimally invasive coronary artery bypass grafting using left internal thoracic artery and saphenous vein grafts provides acceptable graft patency and completeness of revascularization for selected patients with multivessel disease.

Efficacy of amisulpride on postoperative nausea and vomiting: a systematic review and meta-analysis.

AIM AND BACKGROUND: Postoperative nausea and vomiting (PONV) remains a significant clinical problem for surgical patients. Amisulpride is a well-studied D2/D3 antagonist that has the potential to be used for preventing and treating PONV. Our aim was to assess the efficacy and safety of amisulpride for prevention and treatment of PONV through a systematic review and meta-analysis. METHOD: A systematic literature search was performed using MEDLINE, EMBASE, PUBMED, clinicaltrials.gov, and the Cochrane Central Register of Controlled Trials from their inception to Feb 15th, 2019. The efficacy outcome was the incidence of complete response, defined as no emesis and no rescue antiemetic use in a 24-h period after study drug administration. The safety outcomes were the adverse effects associated with amisulpride. RESULTS: Five studies comprising 3243 patients met inclusion critieria. Compared with placebo, amisulpride showed a significantly improved incidence of complete response [relative risk (RR): 1.30; 95% confidence interval (CI): 1.20-1.41; P < 0.00001, I2 = 0%] with firm evidence from the trial sequential analysis. Particularly, the amisulpride at 5 mg dose indicated a significant benefit than placebo [relative risk (RR): 1.28; 95% confidence interval (CI): 1.18-1.39; P < 0.00001, I2 = 4%]. The adverse event profile of amisulpride was generally similar to the placebo. CONCLUSION: Based on our findings, low-dose, intravenous amisulpride is safe and efficacious for the prevention and treatment of PONV compared to placebo. Further studies are needed to explore the optimal dose and timing. CLINICAL TRIAL REGISTRATION: PROSPERO: CRD42019121483.

Interaction-Transferable Graphene-Isolated Superstable AuCo Nanocrystal-Enabled Direct Cyanide Capture.

Noble metals with strong plasmons have been widely used as enhancement substrates for molecule identification. However, cyanide, a toxic and important signaling molecule with a corrosive nature to noble metals, makes direct recognition challenging. Herein a novel superstable magnetic graphene-isolated AuCo nanocrystal (MACG) has been designed. Such graphene isolation enables superior stability without corrosion. Moreover, unexpectedly, although graphene isolated direct contact between Au and cyanide, their interaction was transferable and remained, which gifted MACGs direct cyanide capture capability with no specific ligands needed. Density functional theory calculations and natural bond orbital analysis indicated that the graphene isolation only slightly affected the charge transfer and that a relatively strong interaction was maintained between Au and cyanide. MACGs were utilized for efficient cyanide capture and clearance in various hydrologic environments and sensitive in vivo cyanide capture in C. elegans infected with P. aeruginosa, a pathogen with cyanide as the biomarker, indicating promise for various applications.

Surfactant-Free Interface Suspended Gold Graphitic Surface-Enhanced Raman Spectroscopy Substrate for Simultaneous Multiphase Analysis.

Simultaneous multiphase detection of multiplex analytes is important, albeit challenging, especially in pharmaceuticals analysis since drugs with lipid and water solubility were often administrated together for synergistic therapy. Surface-enhanced Raman spectroscopy (SERS) is a label-free and sensitive tool for multiplex analytes detection at multiphase interfaces. However, the requirements of inducers or surfactant surface modification of the SERS substrate have restricted extensive applications. Herein, we developed a graphene-isolated-Au-nanocrystal based multiphase analysis system. Unexpectedly, the gold graphitic SERS substrate can simply suspend at the interface of the different phase without the involvement of any surfactant. Therefore, the proximity of substrate with analyte molecules remains unaffected. Such suspended substrate not only ensures sensitive SERS detection but also enables the enrichment of analytes from the different phase simultaneously without interference. Moreover, the graphitic shell of the SERS substrate has a unique vibration band located in the Raman biological silence region which is utilized as the internal standard and improves the SERS quantification accuracy. Efficient ex vivo multiphase enrichment and detection of mimic lipid- and water-soluble drugs injected into mice were demonstrated with such gold graphitic substrate, showing the potential of this simultaneous multiplex pharmacokinetic analysis.

Localization of Interacting Dirac Fermions.

Using exact quantum Monte Carlo calculations, we examine the interplay between localization of electronic states driven by many-body correlations and that by randomness in a two-dimensional system featuring linearly vanishing density of states at the Fermi level. A novel disorder-induced nonmagnetic insulating phase is found to emerge from the zero-temperature quantum critical point separating a semimetal and a Mott insulator. Within this phase, a phase transition from a gapless Anderson-like insulator to a gapped Mott-like insulator is identified. Implications of the phase diagram are also discussed.

Design and analysis of tubular permanent magnet linear wave generator.

Due to the lack of mature design program for the tubular permanent magnet linear wave generator (TPMLWG) and poor sinusoidal characteristics of the air gap flux density for the traditional surface-mounted TPMLWG, a design method and a new secondary structure of TPMLWG are proposed. An equivalent mathematical model of TPMLWG is established to adopt the transformation relationship between the linear velocity of permanent magnet rotary generator and the operating speed of TPMLWG, to determine the structure parameters of the TPMLWG. The new secondary structure of the TPMLWG contains surface-mounted permanent magnets and the interior permanent magnets, which form a series-parallel hybrid magnetic circuit, and their reasonable structure parameters are designed to get the optimum pole-arc coefficient. The electromagnetic field and temperature field of TPMLWG are analyzed using finite element method. It can be included that the sinusoidal characteristics of air gap flux density of the new secondary structure TPMLWG are improved, the cogging force as well as mechanical vibration is reduced in the process of operation, and the stable temperature rise of generator meets the design requirements when adopting the new secondary structure of the TPMLWG.

Study on the effect of completely preserving the ejaculatory duct during prostatectomy on reducing postoperative retrograde ejaculation in benign prostatic hyperplasia patients.

Introduction: Preserving the sexual function of benign prostatic hyperplasia (BPH) patients and reducing the incidence of postoperative retrograde ejaculation are critical for BPH patients with sexual needs. Aim: To explore the effect of complete preservation of the seminal tract during transurethral prostatectomy (TURP) on reducing retrograde ejaculation in BPH patients. Material and methods: BPH patients meeting the inclusion criteria were randomly divided into the Control group (traditional TURP) and the Experimental group (complete reserved ejaculatory duct) in a ratio of 1 : 1. Finally, data of 64 BPH patients - 34 in the Control group and 30 in the Experimental group - were analyzed. We measured the preoperative and postoperative maximum urinary flow rate (Qmax), International Prostate Symptom Score (IPSS), Quality of Life (QOL) score, semen volume, and ejaculation function. Results: Compared with pre-operation values, patients in the two groups exhibited increased Qmax and decreased IPSS and QOL scores after the operation. However, there was no significant difference in Qmax, IPSS, or QOL between the Control and Experimental groups after the operation. The two groups of patients had a significant reduction in postoperative ejaculation. Compared with the Control group, the semen volume of patients was higher, and the incidence of retrograde ejaculation was lower in the Experimental group. Conclusions: Prostatectomy with complete preservation of the seminal tract is not different from conventional electrosurgical resection in improving urination symptoms, while the incidence of retrograde ejaculation is significantly lower.

Fracability Evaluation Method of a Fractured-Vuggy Carbonate Reservoir in the Shunbei Block.

The fracability of carbonate reservoirs is a key indicator for evaluating whether reservoirs can be effectively fractured. Taking the fractured-vuggy carbonate reservoir in the Shunbei block as an example, the microscopic characteristics and mechanical properties of this reservoir were analyzed. The test results showed that the core microstructure is relatively dense, the micropores and microfractures are developed, and the mineral composition is characterized by "high carbonate and few impurities". The compressive strength, Young's modulus, and Poisson's ratio of the rock increased with the increase in the confining pressure. Poisson's ratio is more sensitive to confining pressure than Young's modulus and shows the ductile transformation tendency from a low confining pressure to a high confining pressure. Considering the difficulty of forming a complex fracture network, we put forward a "fracture propagation factor" equation constructed with five main factors, including brittleness, fracture toughness, natural fracture, hole size, and horizontal stress difference, and then the fracture propagation factor of Yijianfang formation is calculated to be greater than 0.5. It is known that the Yijianfang formation has higher fracability. On this basis, combined with the construction parameters, a model for evaluating the fracability of a fractured-vuggy carbonate reservoir was established. The comprehensive fracability of four wells in the Shunbei block was calculated by the model. From the calculation results, the comprehensive fracability index of SHB43X was 0.5406 and greater than that of the other three wells, which has a high correlation with the production after fracturing.

Peroxisome proliferator-activated receptor-γ agonists prevent in vivo remodeling of human artery induced by alloreactive T cells.

BACKGROUND: Ligands activating the transcription factor peroxisome proliferator-activated receptor-γ (PPARγ) have antiinflammatory effects. Vascular rejection induced by allogeneic T cells can be responsible for acute and chronic graft loss. Studies in rodents suggest that PPARγ agonists may inhibit graft vascular rejection, but human T-cell responses to allogeneic vascular cells differ from those in rodents, and the effects of PPARγ in human transplantation are unknown. METHODS AND RESULTS: We tested the effects of PPARγ agonists on human vascular graft rejection using a model in which human artery is interposed into the abdominal aorta of immunodeficient mice, followed by adoptive transfer of allogeneic (to the artery donor) human peripheral blood mononuclear cells. Interferon-γ-dependent rejection ensues within 4 weeks, characterized by intimal thickening, T-cell infiltrates, and vascular cell activation, a response resembling clinical intimal arteritis. The PPARγ agonists 15-deoxy-prostaglandin-J(2), ciglitazone, and pioglitazone reduced intimal expansion, intimal infiltration of CD45RO(+) memory T cells, and plasma levels of inflammatory cytokines. The PPARγ antagonist GW9662 reversed the protective effects of PPARγ agonists, confirming the involvement of PPARγ-mediated pathways. In vitro, pioglitazone inhibited both alloantigen-induced proliferation and superantigen-induced transendothelial migration of memory T cells, indicating the potential mechanisms of PPARγ effects. CONCLUSION: Our results suggest that PPARγ agonists inhibit allogeneic human memory T cell responses and may be useful for the treatment of vascular graft rejection.

Long noncoding RNA LOC100911498 is a novel regulator of neuropathic pain in rats.

INTRODUCTION: Neuropathic pain (NP) is the most debilitating of all clinical pain syndromes and may be a consequence of dysfunction in the somatosensory nervous system. Unfortunately, the pathogenesis of NP is not fully understood yet and it cannot be cured totally. Long noncoding RNA (lncRNA) is a type of RNA molecule greater than 200 nucleotides, and dysregulated expression of lncRNAs play a critical role in the facilitation of NP. Previous study showed the expression level of LOC100911498 in the spinal cords of spared nerve injury (SNI) rats were increased. This research was aimed at exploring what role LOC100911498 plays in the pathophysiological process of NP. METHODS: The mechanical withdrawal threshold (MWT) of rats was measured by the von Frey test. The expression levels of P2X4 receptor (P2X4R), ionized calcium-binding adaptor molecule 1 (Iba-1), p-p38 and brain-derived neurotrophic factor (BDNF) in spinal cords were detected, respectively. RESULTS: Our results suggested that the level of LOC100911498 in SNI rats was markedly higher than that in the sham group; the MWT values in rats were treated with LOC100911498siRNA were increased, and the expression levels of P2X4R, Iba-1, p-p38 and BDNF in SNI+ LOC100911498siRNA group were reduced compared with those in the SNI group. CONCLUSION: Our study indicated the effects lncRNA LOC100911498 siRNA exerted on NP were mediated by P2X4R on microglia in the spinal cords of rats. Further, LOC100911498 may be a novel positive regulator of NP by regulating the expression and function of the P2X4R.

Combining Intravoxel Incoherent Motion Diffusion Weighted Imaging and Texture Analysis for a Nomogram to Predict Early Treatment Response to Concurrent Chemoradiotherapy in Cervical Cancer Patients.

This study aimed to predict early treatment response to concurrent chemoradiotherapy (CCRT) by combining intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) with texture analysis (TA) for cervical cancer patients and to develop a nomogram for estimating the risk of residual tumor. Ninty-three cervical cancer patients underwent conventional MRI and IVIM-DWI before CCRT. We conducted TA using T2WI. The patients were allocated to partial response (PR) and complete response (CR) groups on the basis of posttreatment MRI. Multivariate logistic regression analysis on IVIM-DWI parameters and texture features was employed to filter the independent predictors and construct the predictive nomogram. Its discrimination and calibration performances were estimated. Multivariate analysis on the IVIM-DWI parameters showed that D and f were independent predictors (OR = 4.029 and 0.889, resp.; p < 0.05). However, the multivariate analysis on the texture features indicated that GLCM-correlation, GLRLM-LRE, and GLSZM-ZE were independent predictors (OR = 43.789, 9.774, and 23.738, resp.;p < 0.05). The combination of IVIM-DWI parameters and texture features exhibited the highest predictive performance (AUC = 0.975). The nomogram to identify the patients with high-risk residual tumors exhibited an acceptable predictive performance and stability with a C-index of 0.953. Decision curve analysis demonstrated the clinical use of the nomogram. The results demonstrate that D, f, GLCM-correlation, GLRLM-LRE, and GLSZM-ZE were independent predictors for cervical cancer. The nomogram combining IVIM-DWI parameters and texture features makes it possible to identify cervical cancer patients at a high risk of residual tumor after CCRT.

In vivo activation of pH-responsive oxidase-like graphitic nanozymes for selective killing of Helicobacter pylori.

Helicobacter pylori infection is a major etiological factor in gastric diseases. However, clinical antibiotic therapy for H. pylori is limited by continuously decreased therapeutic efficacy and side effects to symbiotic bacteria. Herein, we develop an in vivo activatable pH-responsive graphitic nanozyme, PtCo@Graphene (PtCo@G), for selective treatment of H. pylori. Such nanozymes can resist gastric acid corrosion, exhibit oxidase-like activity to stably generate reactive oxygen species only in acidic gastric milieu and demonstrate superior selective bactericidal property. C18-PEGn-Benzeneboronic acid molecules are modified on PtCo@G, improving its targeting capability. Under acidic gastric pH, graphitic nanozymes show notable bactericidal activity toward H. pylori, while no bacterial killing is observed under intestinal conditions. In mouse model, high antibacterial capability toward H. pylori and negligible side effects toward normal tissues and symbiotic bacteria are achieved. Graphitic nanozyme displays the desired enzyme-like activities at corresponding physiological sites and may address critical issues in clinical treatment of H. pylori infections.

A sustainability anti-infective pharmaceutical wastewater treatment technology: multi-stage vertical variable diameter membrane bioreactor with DO online controlling.

The proper choice of dissolved oxygen (DO) is important in aerobic treatment. In this paper, a multi-stage vertical variable diameter membrane bioreactor was developed to treat pharmaceutical wastewater containing 6-APA and ceftriaxone sodium. In the 180 days of operation, the performance of COD, BOD5, 6-APA, ceftriaxone sodium removal, sludge index, and microbial enzyme activity under different DOs (from 0.5 to 6.0 mg/L) were investigated. The results showed that the optimal range of DO was 1.5-2.1 mg/L, and the highest removal rates of COD and BOD5 were observed 87.3%±2.4% and 95.3%±1.8%, the corresponding effluent COD and BOD5 were 189 mg/L and 24 mg/L, respectively. To reduce the energy consumption and ensure stability of DO in the reactor, a control strategy based on an improved differential evolution BP fuzzy neural network was built and found that the performance and cost of the controlled DO were improved effectively than that of uncontrolled DO.

Multiple draft tubes airlift loop membrane bioreactor as an efficient system for acidic 7-amino cephalosporanic acid (7-ACA) wastewater treatment.

In this study, a lab-scale multiple draft tubes airlift loop membrane bioreactor (Mt-ALMBR) was used for treating acidic 7-amino cephalosporanic acid (7-ACA) wastewater under different pHs (3.54-6.20) and hydraulic retention time (HRT) (48 h, 36 h, 24 h and 16 h). During about 200 days operation, under HRT of 48 h and pH condition about 6.0, the optimum average COD and BOD5 removal rates were reach to 84.4 ± 2.1% and 94.9 ± 0.8%, and the highest 7-ACA removal rate also observed as 77.6%. Biodegradation, membrane rejection, hydrolysis and sludge adsorption were the four main pathways of 7-ACA removal. With the increase of pH, biodegradation, membrane rejection and hydrolysis had significant positive impacts on 7-ACA removal, while adsorption had a negative impact. Moreover, mathematical models for 7-ACA removal rate and pH were calculated to guide the operation of Mt-ALMBR. Biodegradation was the main pathway to remove 7-ACA when pH was >4.17.

Performance of an up-flow anaerobic bio-electrochemical system (UBES) for treating sulfamethoxazole (SMX) antibiotic wastewater.

This paper focused on the feasibility and performance of an up-flow anaerobic bio-electrochemical system (UBES) for treating sulfamethoxazole (SMX) antibiotic wastewater at different COD loading rates (LRs) from 2.02 ± 0.13 to 6.09 ± 0.14 kgCOD/(m3·d). Open-circuit UBES had a lower average COD removal rate of 62.4 ± 4.7% in Run2, and the accumulation of volatile fatty acid (VFA) was occurred. However, closed-circuit UBES can alleviate the accumulation of VFA (which was decreased from 720.4 to 102.4 mg/L), the highest average COD, SMX removal rates were 85.7 ± 3.2% and 73.7 ± 2.0%, respectively. The closed-circuit UBES can withstand more than 3 times LR than open-circuit UBES, which proved that the ability of microorganisms to resist toxic substance stress was strengthened. And the mathematical models for pollutants removal rate were established and well interpreted the results, which also can guide the operation of UBES.

Antiferromagnetically ordered Mott insulator and d+id superconductivity in twisted bilayer graphene: a quantum Monte Carlo study.

Using exact quantum Monte Carlo method, we examine the recent novel electronic states seen in magic-angle graphene superlattices. From the Hubbard model on a double-layer honeycomb lattice with a rotation angle θ=1.08°, we reveal that an antiferromagnetically ordered Mott insulator emerges beyond a critical Uc at half filling, and with a small doping, the pairing with d+id symmetry dominates over other pairings at low temperature. The effective d+id pairing interaction strongly increases as the on-site Coulomb interaction increases, indicating that the superconductivity is driven by electron-electron correlation. Our non-biased numerical results demonstrate that the twisted bilayer graphene shares the similar superconducting mechanism of high temperature superconductors, which is a new and ideal platform for further investigating the strongly correlated phenomena.

Investigation of Water-Sensitivity Damage for Tight Low-Permeability Sandstone Reservoirs.

Tight sandstone reservoir has been characterized by low permeability and porosity, developed micro-nanopore throats, strong capillary forces, and high content of clay minerals. It is vulnerable to damage caused by water sensitivity during the processes of reservoir development, which significantly impedes the hydrocarbon production. Hence, it is important to analyze the damage mechanism of water sensitivity to avoid the production decrease. However, the conventional steady-state method is time-consuming and inaccurate for evaluating the water-sensitivity damage in tight low-permeability reservoirs. Aiming at this problem, this paper introduced pressure transmission test (PTT), a time-saving and accurate method, to quantitatively evaluate the degree of damage by water sensitivity. Moreover, lithofacies analysis methods, consisting of computed tomography (CT) scanning, scanning electron microscopy (SEM), and X-ray diffraction (XRD), are also used to evaluate the reservoir properties, which can provide a basis for analyzing the potential damage factors. The CT scanning results show that the developed micropore throat in the target reservoirs has poor connectivity. The XRD results indicate that the target reservoir mainly consists of a mixed-layer illite/smectite and smectite, which is consistent with the observation by SEM experiments. The results of PTT show that the ultimate average damage rate of water sensitivity is approximately 62.94%, attributed to the medium-strong water sensitivity. Compared with the conventional steady-state method measuring the outlet flow of the core, this method can reduce the experimental errors merely by recording the pressure data varying with time. Moreover, it is also applicable for evaluating other types of formation sensitivity damage, such as alkali and acid sensitivity damage for low-permeability reservoirs.

Transient Pressure Analysis of Volume-Fractured Horizontal Wells Considering Complex Fracture Networks and Stress Sensitivity in Tight Reservoirs.

Tight reservoirs, as an important alternative for conventional energy resources, have been successfully exploited with the aid of hydraulic fracturing technologies. Because of the inherent ultralow permeability and porosity, tight oil reservoirs generally suffer from the effects of stress sensitivity. Both hydraulic fractures with complex geometries and a high-permeability area known as stimulated reservoir volume (SRV) may be generated by the massive hydraulic fracturing operations. All these bring huge challenges in transient pressure analysis of tight reservoirs. Up till now, although many research studies have been carried out on the transient pressure analysis of volume-fractured horizontal wells in tight reservoirs, unfortunately, there is still a lack of research studies that have taken stress sensitivity, complex fracture networks, and the SRV into consideration, simultaneously. To fill up this gap, this paper first idealizes the reservoir after hydraulic fracturing as two radial composite regions, that is, the unstimulated outer region and the inner SRV. The stress sensitivity is characterized by the variable permeability depending on the pore pressure. A linear source with consideration of the stress sensitivity in the composite reservoir is obtained by the perturbation technique, Laplace transformation, and the flow coupling of two regions. Second, the complex fracture networks are discretized into segments to capture their geometries. A semi-analytical model is finally established and validated by the comparison with previous models. On the basis of our model, six flow stages of volume-fractured horizontal well are identified and special features of each regime are analyzed. The stress sensitivity has a great impact on the later stage of production. The mobility ratio and the SRV radius mainly affect SRV pseudo-steady-state flow period and interporosity flow period in the outer region. Fracture number mainly affects the linear flow in the SRV. Fracture geometries mainly affect linear flow and interporosity flow in the SRV. This study has some significance for well test interpretation and production performance analysis of tight reservoirs.