Recovery Degree Research Articles

Effects of Two Quinolone Antibiotics on Growth of Four Species of Planktonic Algae

Quinolone antibiotics, especially enrofloxacin and ciprofloxacin, are currently found to be at high levels commonly in natural waters. Studying the effects of these two quinolones on the growth of common microalgae in water is valuable for understanding the ecological effects of quinolones in the aquatic environment. Therefore, the effects of different concentrations of enrofloxacin and ciprofloxacin hydrochloride on the population growth of four species of planktonic microalgae (Chlorella vulgaris, Tetradesmus obliquus, Scenedesmus quadricauda, and Microcystis aeruginosa) were studied. The results showed that there was a significant effect-dose regression relationship between the concentration of nofantibiotic and the growth inhibitory rate of the algae population. The 96h half maximal inhibitory concentration (96h-IC50) of enrofloxacin on T. obliquus, S. quadricauda, M.aeruginosaI and C. vulgaris were 195.6, 88.8, 56.1, and 22.6 mg/L respectively, and the order of sensitivity of the four microalgae to enrofloxacin was T. obliquus＜S. quadricauda＜M. aeruginosa＜C. vulgaris. Another 96h-IC50 of ciprofloxacin hydrochloride to S. quadricauda, T. obliquus, M. aeruginosa, and C. vulgaris were 588.6, 546.3, 49.8, and 44.7 mg/L respectively. The sensitivity of the four microalgae to ciprofloxacin hydrochloride was ranked as follows: S. quadricauda＜T. obliquus＜M. aeruginosa＜C. vulgaris. Among the four species of planktonic microalgae, two species of Scenedesmus were less sensitive to the quinolone antibiotics. Therefore, these two species of Scenedesmus were more resistant to the two quinolone antibiotics, while C. vulgaris was the most sensitive to them. According to the data of IC50, the toxicity of enrofloxacin to three green microalgae was higher than that of ciprofloxacin, while the toxicity of enrofloxacin to M. aeruginosa was lower than that of ciprofloxacin. The population growth of the four planktonic microalgae was inhibited in the first 4 days after being treated by these two quinolone antibiotics, but the microalgae could gradually detoxify and restore their population growth after 96 h. Moreover, the toxicity of enrofloxacin to the four algae increased with time. The toxicity of ciprofloxacin hydrochloride to T. obliquus and S. quadricauda increased, and the toxicity to M. aeruginosa and C. vulgaris decreased. The recovery degree of ciprofloxacin hydrochloride was at least 39% higher than that of enrofloxacin. Low concentrations of enrofloxacin (<36mg/L) provoked a higher density of M. aeruginosa than that of the control group after 10 days of exposure. In this case, the algal density of M. aeruginosa could be more than 107 cells/L when the concentration of enrofloxacin was below 36mg/L.

Influence of micro-heterogeneity of fractured-porous reservoirs on the water flooding mobilization law

The storage space of fractured-porous reservoirs includes a variety of primary pores, secondary pores and fractures and has strong micro-heterogeneity. When water injection is used for development, the development effects of different development areas are significantly different. In order to clarify the influence of micro-heterogeneity on the water flooding mobilization law, three types of glass etching models were designed according to actual oilfield. Water flooding experimental research was conducted on the models. The results show that the mobilization mode changes from a uniform mobilization mode to a network mobilization mode as the heterogeneity of the pore system increases. The recovery degree of pore throat structure I model is 31.8% lower than that of pore throat structure II model. The fracture system of fractured-porous reservoirs is shown as a finger-like mobilization mode along with the fractures. This model has a 19.8% lower recovery degree than pore throat structure II model but 12% higher than pore throat structure I model. The water flooding law was studied from the utilization order of large and small pore throats, and the shape of water flooding front was compared and analyzed, which provides a guiding significance for the enhanced oil recovery of fractured-porous reservoirs.

Study on CO2–Water Co-Injection Miscible Characteristics in Low-Permeability Near-Critical Volatile Oil Reservoir

Low-permeability near-critical volatile reservoirs are characterized by light oil, complex fluid phase, and strong reservoir inhomogeneity, etc. Purely injecting CO2 will create a series of problems, such as serious gas channeling, low sweep efficiency, and low oil recovery. Therefore, in this paper, through a combination of experiments and simulations and in the process of studying the problem from simple to complex, we carried out phase equilibrium experiments for CO2-near-critical volatile oil and CO2-near-critical volatile oil-formation water, as well as experiments for minimum miscible pressure of slim-tube with pure CO2 and CO2–water co-injection to the comparative study of the miscible characteristics and displacement oil efficiency between pure CO2 injection and CO2–water co-injection. It provides an important reference for improving oil recovery by CO2–water co-injection in low-permeability near-critical volatile reservoir. The results of CO2-near-critical volatile oil/CO2-near-critical volatile oil-formation water phase equilibrium experiments show that the saturation pressure, density, and gas–oil ratio of the system increase, and the viscosity decreases with the increase in CO2 injection. In the three-phase system of CO2-near-critical volatile oil-formation water, the CO2 content in the flash gas of crude oil, gas–oil ratio, and gas–water ratio are negatively correlated with the water saturation. The results of slim-tube experiments and simulations on the miscible characteristics and displacement oil efficiency of pure CO2 injection and CO2–water co-injection show that the recovery degree of crude oil under CO2–water co-injection is higher than that of pure CO2 injection, and the CO2 dissolved transition section in oil and gas is shorter and the gas breakthrough time is later under CO2–water co-injection, which effectively increases the sweep efficiency and improves the degree recovery of crude oil. When CO2–water co-injection, the ratio of water is higher, the later the gas–oil ratio rises, the later the CO2 breakthrough, and the higher the degree of crude oil recovery. It indicates that when CO2–water co-injection, the ratio of water is higher, the more CO2 is dissolved in water, which effectively inhibits the occurrence of gas channeling and increases the sweep area, thus improving the degree recovery of crude oil. The research results of this paper provide an experimental basis and theoretical foundation for CO2–water co-injection for enhanced crude oil recovery in low-permeability near-critical volatile reservoirs.

Experimental Study on the Seepage Characteristics of Multilayer Commingled Production and Influencing Factors of the Development Effect in Low-Permeability Tight Sandstone Gas Reservoirs.

For low-permeability tight sandstone gas reservoirs, multilayer commingled production technology is usually adopted by a large number of production wells. This production method can significantly increase the productivity of a single well, thereby improving the efficiency of gas field development. To have a better understanding of the seepage characteristics of multilayer commingled production of the SXM (ShaXiMiao) Formation tight sandstone gas reservoirs, an indoor physical simulation experiment of commingled injection and separate production using double-pipe parallel long cores was designed under influencing factors such as formation pressures, permeability contrast, and water saturations. Finally, the contribution of high- and low-permeability reservoirs to the total production capacity under different conditions is clarified, which provides a reference for formulating reasonable development strategies for gas reservoirs. Through the experimental study, we found that the recovery degree of the high-permeability formation is higher than that of the low-permeability formation during the depletion production process. The combination of depletion development and water flooding can greatly increase the recovery degree of gas reservoirs. Under the same production pressure difference condition, the higher the formation pressure and the permeability, the higher the production capacity. If the water saturation increases, the production contribution rate of the high-permeability layer gradually increases, and the production contribution rate of the low-permeability layer gradually decreases.

Deformation and seepage properties of raw coal during the simultaneous loading and unloading of axial stress and confining pressure

The mining of coal resources causes the stress on the front and both sides of the working face to be in a complex loading and unloading process, and the gas contained in the coal body migrates, which can cause gasdynamic disasters in severe cases. Therefore, this study designed a three-dimensional stress path based on the in situ stress distribution characteristics of the No. 2461 working face and conducted the experiment on the deformation and seepage characteristics of raw coal under simultaneous unloading (loading) axial stress and loading (unloading) confining pressure. It is considered that in the process of loading axial stress, the volumetric strain increases gradually with the increase in effective stress, and the permeability decreases exponentially with the increase in effective stress. In the process of simultaneous unloading axial stress and loading confining pressure, the volumetric strain of coal sample increases with the increase in effective stress, and the permeability decreases exponentially with the increase in effective stress. However, the processes of simultaneous loading axial stress and unloading confining pressure are opposite, and the variation curves of the two do not overlap, indicating that the coal sample undergoes elastic-plastic deformation after cyclic loading, the permeability cannot be restored to the initial state, and the volumetric strain further expands. The permeability damage rate and maximum permeability damage rate are used to evaluate the recovery degree and reduction range of coal samples' permeability. The volume expansion rate and maximum volume expansion rate are used to evaluate the expansion degree and increase range of coal samples' volume.

Study on the Compatibility between Combined Control of Channel Plugging and Foam Flooding and Heterogeneous Reservoirs—Taking Bohai Z Oilfield as an Example

With the oilfield developed to a later stage and its heterogeneity gradually becoming more serious, the adaptability of conventional profile control technologies for the reservoir becomes worse and worse. Therefore, the fitness of compatibility between combined patterns of profile control and target reservoir becomes an important factor for the efficient development of the oil field. Due to the importance of compatibility between the profile control and reservoir property, research on the remaining oil recovery with combined patterns of profile control and foam flooding were carried out. The experimental results showed that the combined profile control is highly consistent with the target reservoir. With a little lower initial viscosity (28.3–40.9 mPa·s), the channel plugging system is easy to inject. Due to the addition of a polymer, the reinforced foam is not easy to defoam when transporting in the pore throats of the core sample, and its spontaneous adaptability makes it match with the porous media of the formation automatically, which effectively prolongs the transporting distance for the foam in the deep part of the core sample. The segment plug with a gel-type profile control agent injected at the front stage is of great significance to the non-homogeneous reservoir, so it is necessary to inject a sufficient gel-type profile control agent into the high permeability layer to make it produce a seal. When the permeability differential was equal to 10, the maximum increase of oil recovery degree was 29.69%, and the development effect became worse after increasing or decreasing the permeability differential.

Risk factors of adjacent vertebral refracture after percutaneous vertebroplasty for osteoporotic vertebral compression fractures in super-old patients

To analyze the risk factors for refracture of adjacent vertebrae after percutaneous vertebroplasty (PVP) in super-old patients with osteoporotic vertebral compression fractures(OVCFs). A retrospective analysis was performed on 40 patients(age≥90 years) with OVCFs who underwent PVP between June 2012 and June 2019. There were 7 males and 33 females, age from 90 to 101 years old with an average of (94.6±1.6) years. Patients were divided into two groups according to whether adjacent vertebral refracture occurred after PVP. Among them, 20 patients occurred refracture after PVP (refracture group) and 20 patients did not occur it(control group). The general information, radiological data and pelvic parameters of the two groups were collected. The items included age, gender, body mass index (BMI), fracture site and bone mineral density(BMD) T-value, fracture to operation time, compression degree of injured vertebra, recovery degree of anterior edge of injured vertebra, bone cement injection amount, bone cement leakage, pelvic index(PI), pelvic tilt angle (PT), sacral angle(SS), et al. Factors that may be related to refracture were included in the single-factor study, and multivariate Logistic regression analysis was performed on the risk factors with statistical significance in the single-factor analysis to further clarify the independent risk factors for refracture of adjacent vertebral bodies after PVP. There were no significant differences in age, gender, fracture site, fracture to operation time, compression degree of injured vertebra and recovery degree of anterior edge of injured vertebra between two groups (P>0.05). There were significant differences in BMI, BMD T-value, bone cement injection amount and bone cement leakage rate between two groups(P<0.05). The PI and PT values of the refracture group were higher than those of the control group(P<0.05). There was no significant difference in SS between two groups (P>0.05). Multivariate Logistic regression analysis showed that decreased BMD T-value, bone cement leakage, increased PT and PI values increased the risk of recurrence of adjacent vertebral fractures in OVCFs (P<0.05). There are many risk factors for the recurrence of adjacent vertebral fractures in super-old patients with OVCFs. Patients with high PI and PT values may be one of the risk factors.

Residual oil retention and stripping mechanism of hydrophilic pore surfaces during CO2 and N2 combined gas flooding

The mixed gas of CO2 and N2 can replace the great mass of the remaining oil in the center of the porous media channel, but the surface of the pore channels still retain more residual oil. Most of the previous studies focused on how to displace the residual oil in the center of the pore passages, while ignoring how to enhance the recovery degree of the residual oil on the pore surfaces. Moreover, there are few research results on the mechanism of residual oil retention and stripping on pore surfaces during CO2–N2 combined gas flooding, which need to be improved and supplemented. In this paper, the microscopic interaction process among gas phase, oil phase and pore surfaces were explored by molecular dynamics, the changes in microstructural between n-decane molecules and the spatial distribution of gas molecules and n-decane molecules in the system was clarified. The interaction energy between gas, n-decane and pore surfaces were analyzed to reveal the mechanism of remaining oil retention and stripping. The results indicated that when only CO2 in the gas phase, the oil films were easily divided by CO2 molecules, and the adsorption layer formed by CO2 molecules on the quartz surface could well detach the oil phase from the quartz surfaces. With the increase of the proportion of N2 in the mixed gas, the interaction energy between the gas and n-decane phase and between the gas phase and pore surfaces decreased, and the capacity of the gas phase to peel off the oil films from the pore surfaces was weakened. When the proportion of N2 in the gas phase exceeded 25%, the gas phase has no ability to peel off the oil films from the quartz surfaces. The research results have guiding significance for the CO2-N2 combined gas flooding to further tap the remaining oil.

Mathematical Methodology in the Seismic Resilience Evaluation of the Water Supply System

Abstract This paper has collected more than one hundred papers about resilience at home and abroad, summarised and analysed the meaning and evaluation methods of resilience and then summarised the key issues. Through research on these papers, we found that the current evaluation method for the water supply system seismic resilience is divided into two aspects: on the one hand, it’s based on the seismic performance of water supply system, where the system itself evaluates the resilience absorbs the earthquake resistance level. On the other hand, the assessment is based on the post-earthquake recovery ability of the water supply system, namely the recovery time, recovery degree, recovery path and the resilience level of resources input. Based on past seismic safety of the water supply system and research on post-earthquake recovery ability, the meaning of water supply system in seismic resilience should include two aspects of seismic safety and post-earthquake recovery ability. From using the seismic safety evaluation method also and post-earthquake recovery ability in two angles, this paper gives a comprehensive multiple evaluation index framework of the evaluation model and points out that water system earthquake state resilience evaluative criteria and the requirements of the current seismic code should match.

A comparison between cisatracurium and rocuronium-induced neuromuscular block on laryngeal electromyography recovery after neostigmine reversal in a porcine model.

BackgroundInducing and reversing neuromuscular block is essential to a positive outcome of thyroid surgery, with intraoperative neuromonitoring (IONM) being used to decrease recurrent and superior laryngeal nerve injuries and improve vocal outcome. Neostigmine is a non-specific broad-spectrum and inexpensive reversal agent for neuromuscular blocking agents (NMBAs). The aim of this porcine study was to explore the effect of neostigmine on electromyography (EMG) signal recovery profile following the commonly used NMBAs, cisatracurium and rocuronium.MethodsTwelve piglets were allocated into two groups with six piglets in each group. When stable baseline EMG signals were obtained, a neuromuscular block was induced by intravenous cisatracurium 0.2 mg/kg (group C) or rocuronium 0.6 mg/kg (group R) for each piglet. We compared laryngeal EMG tracing with spontaneous recovery (control) and neostigmine (0.04 mg/kg) reversal for each group. The time course of real-time laryngeal EMG signals was observed for 30 min from NMBA injection. Effects of neostigmine on EMG signal were assessed at 50% EMG recovery and by the maximum neuromuscular block recovery degree from the baseline value.ResultsNeostigmine shortened the recovery time to 50% EMG amplitude in both group C (16.5 [2.5] vs. 29.0 [2.0] min, P<0.01) and group R (16.5[2.5] vs. 26.5 [1.5] min, P<0.05) compared to spontaneous recovery, respectively. Neostigmine reversal also enhanced the maximum degree of EMG amplitude recovery in both group C (83.6 [5.1] vs. 47.2 [6.1] %, P<0.01) and group R (85.6 [18.2]vs. 57.1 [6.3] %, P<0.05) compared to spontaneous recovery, respectively. The reversal effect of neostigmine did not differ significantly between cisatracurium and rocuronium.ConclusionsThis porcine model demonstrated that neostigmine provides an adequate and timely IONM signal suppressed by both cisatracurium and rocuronium. These results can potentially expand the options for precision neuromuscular block management during IONM to improve vocal outcomes in thyroid surgery patients.

The Identification and Reservoir Architecture Characterization of Wandering Braided River in Nanpu 1-29 Area, Bohai Bay Basin

Nanpu 1-29 Area of Jidong Oilfield in China is currently in the stage of high water cut and low recovery degree. The remaining oil development and adjustment are difficult because of the complex reservoir heterogeneity and the lack of analysis of the reservoir architecture due to the unclear river type. This study first used sedimentary background, granularity, core, and sand body distribution to determine the river type and believed it belongs to the wandering braided river. Combined with core and logging data, four types of sedimentary architectural elements were found in the study area, namely, channel bar, braided channel, floodplain, and basalt. Based on the scale measurement of many similar modern wandering braided rivers, core data, and empirical formulas, the scales of the braided rivers were determined. The quantitative relationships among the scale of the braided river, the channel bar, and the braided channel were established. With this constraint, the reservoir architecture was anatomized. The results showed two filling types of the braided channels, including sandy filling and muddy filling. The combination patterns of the channel bars and the braided channels could be divided into three types, namely, superimposed, standalone, and contact, and the contact type was the primary type. On the whole, it showed the geometric morphological characteristics of the flat top convex at the bottom of the channel bar and the flat bottom convex at the top of the braided river channel. A careful measure of the architectural element was executed. The length of the single braided flow belts was 365.16-1349.72 m, and the width was 270.57-1160.54 m. The channel bar’s length was distributed 158.89-318.32 m, and the width was distributed 75.97-116.41 m. The braided river’s width was distributed 16.81-180.05 m. The length and width ratio of the channel bar was concentrated between 2 and 4, which manifested wide bar and narrow river channel mode. Finally, the static distribution model and dynamic response curve were compared to verify the correctness of the reservoir architecture characteristics to guide the subsequent development of the oilfield.

Effect of Holistic Nursing Intervention Based on Nursing Procedure on Intestinal Function Recovery and Pain Degree after Thoraco-lumbar Spinal Fracture

Effect of Holistic Nursing Intervention Based on Nursing Procedure on Intestinal Function Recovery and Pain Degree after Thoraco-lumbar Spinal Fracture

A Quantitative Relationship between Oxidation Index and Chalcopyrite Flotation Recovery

The surface oxidation of chalcopyrite is one of the most important factors affecting its flotation performance. In this study, a critical oxidation degree is proposed to define “slight” and “significant” oxidation in terms of surface species and chalcopyrite flotation recovery. Slight oxidation enhanced chalcopyrite hydrophobicity, but significant oxidation reduced its recovery apparently. Microthermokinetic measurements indicated that the apparent activation energy (Ea) of chalcopyrite oxidation was reduced from around 173 kJ·mol−1 to 163 kJ·mol−1 when the reaction changed from slight oxidation to significant oxidation when applying H2O2. The surface oxidation degree was defined as the ratio of hydrophilic species to hydrophobic species. The highest recovery (94.8%) and contact angle (93°) were achieved at a concentration of 0.1 vol.% H2O2, with the lowest oxidation degree of 0.388 being observed. The oxidation degree was correlated to the flotation recovery, with a quantitative relationship (y = −298.81x + 213.05, y and x represent flotation recovery and oxidation degree, respectively, 0.388 ≤ x ≤ 0.618) being established, thereby giving a guideline to better manage chalcopyrite flotation by controlling its surface oxidation and SBX adsorption on chalcopyrite surfaces.

Experimental Study of Oil Displacement and Gas Channeling during CO2 Flooding in Ultra—Low Permeability Oil Reservoir

Aiming to solve the problems of poor CO2 displacement efficiency and serious gas-channeling and low well-opening rates in ultra-low permeability reservoirs, we carry out CO2 displacement experiments under different permeability reservoirs by using different development methods, water drive to gas drive procedures, and different fracture positions to clarify the effects of physical formation properties, injection methods, and fracture parameters on CO2 displacement efficiency in C8 ultra-low permeability reservoirs. The experimental results show that the recovery degree of CO2 miscible drive increases with an increase in permeability. When the gas–oil ratio is greater than 2000 m3/m3, serious gas channeling can be observed in both the miscible drive and immiscible drive. In addition, when the water drive is altered to be a gas drive, the water cut of 0.45 mD and 0.98 mD cores decreased, and the recovery degree increased by 13.4% and 16.57%, respectively. A long fracture length will deteriorate gas channeling and lower the CO2 oil-displacement efficiency. However, the fracture location is found to have little impact on the recovery of CO2 displacement.

Assessing the restoration status and potential of ecosystem services on the Loess Plateau

An ecosystem service assessment can directly reflect the effectiveness of ecological restoration, reveal the process and driving mechanism of ecosystem change, and guide the future management. However, most studies have focused on analyzing the historical dynamic changes in ecosystem services (ESs), and few studies have clarified what level the ecosystem should be restored to. Therefore, this study proposed the concept of a zonal climax background based on the ESs in natural reserves, which can present the best state of ecosystem in the same region. We regarded the zonal climax background as the ultimate goal of ecological restoration, and described the recovery process and gap compared with the actual state. Taking the forest, grassland and wetland ecosystems of the Loess Plateau (LP) as the research object, we quantitatively simulated the zonal climax background and actual conditions of carbon fixation, water conservation, soil conservation and sand fixation. The results showed that the annual average carbon fixation of the zonal climax background of the LP was 44.88 MgC/km2/a, the water conservation was 4.39 × 106 m3/km2/a, the soil conservation was 8416.64 t/km2/a and the sand fixation was 1051.97 t/km2/a, which represented the annual average recovery degrees were 94.10%, 38.46%, 64.73% and 87.59%, respectively. In addition, the study categorized the four ESs of the regionalization of comprehensive control of the LP through the superimposed analysis of the recovery space and the recovery degree and clarified the main focus of future ES improvement, such as carbon fixation in the loss hilly and valley region (LHGR) and Loss Plateau valley region (LPGR); soil conservation in the LHGR, LPGR and earth rock mountains area (ERMA); and water conservation in the LHGR and plain area (PA). Water and soil conservation in irrigated regions (IRs) and sandy areas (SAs) were not the main ESs and should not be prioritized over other ESs.

An analytical model to evaluate the resilience of shield tunnel linings considering multistage disturbances and recoveries

The assessment of shield tunnel linings is a key activity for ensuring the operational safety of trains. This paper proposed an analytical model for evaluating the resilience of shield tunnel linings considering multistage disturbances and recoveries on the basis of resilience theory. The resilience metric of the tunnel linings was calculated according to a multistage resilience analysis model established by this paper. The diameter convergence and settlement of the tunnel were chosen as the performance indicators based on the different responses of the tunnel linings under loading and unloading conditions. The classification standard for the resilience of the tunnel linings was suggested according to existing research results. Then, the influences of the performance recovery degree and decision-making time on the tunnel linings resilience were discussed. Finally, the analytical model proposed in this paper was applied to the case of basement excavation beside existing tunnels. The results showed that the resilience metric obtained by different linings performance indicators was obviously different. For excavation beside existing tunnels, only taking diameter convergence as the performance indicator of the tunnel linings caused the calculation results to be high, that is, the linings resilience was overestimated. From the case in this paper, the settlement of the tunnel should be given more attention. In addition, the existence of the evolution stage in the performance degradation curve significantly reduced the resilience of the tunnel linings. The research results in this paper will provide important references for the safety assessment of shield tunnels and the performance recovery of damaged linings.

Microscopic production characteristics of crude oil in nano-pores of shale oil reservoirs during CO2 huff and puff

The parameters such as pore size distribution, specific surface area and pore volume of shale rock samples are analyzed by low-temperature nitrogen adsorption experiment, and then the conversion coefficient between relaxation time (T2) and pore size is calibrated. Nuclear magnetic resonance experiments of CO2 huff and puff in shale samples are carried out to study the effects of gas injection pressure, soaking time and fractures on the oil production characteristics of shale pores from the micro scale. The recovery degrees of small pores (less than or equal to 50 nm) and large pores (greater than 50 nm) are quantitatively evaluated. The experimental results show that the recovery degree of crude oil in large pores increases rapidly with the increase of injection pressure under immiscible conditions, and the effect of injection pressure rise on recovery degree of large pores decreases under miscible conditions; whether miscible or not, the recovery degree of crude oil in small pores basically maintains a linear increase with the increase of injection pressure, and the lower size limit of pores in which oil can be recovered by CO2 decreases with the increase of gas injection pressure; with the increase of soaking time, the recovery degree of crude oil in large pores increases slowly gradually, while the recovery degree of crude oil in small pores increases faster and then decelerates, and the best soaking time in the experiments is about 10 h; the existence of fractures can enhance the recovery degrees of crude oil in small pores and large pores noticeably.

Determination of Reasonable Bottom-Hole Pressure in Unconventional Tight Oil Reservoirs: A Field Case Investigation

Abstract The bottom-hole flow pressure is an important factor affecting the production of the unconventional tight oil well. The reasonable bottom-hole flow pressure has a positive effect on enhancing the production capacity of oilfields and improving the production efficiency of oilfield enterprises. Therefore, a robust method is proposed to determine the reasonable bottom-hole flow pressure in unconventional tight oil reservoirs, sharing the advantages of coupling geological feature and fluid flow behavior. In this method, the geological model and numerical reservoir simulation based on ECLIPSE software are developed firstly. The effects of the stress sensitivity, the PVT properties, permeability damage, fracturing fluid leak-off, and skin coefficient on the single-well productivity are then discussed. The reasonable variation range of the bottom-hole flow pressure in different production stages is then determined. Results show that crude oil viscosity, formation damage, and stress sensitivity are the most sensitive factors to the recovery degree. And, desirable tight oil production performance can be achieved with the application of the optimized bottom-hole pressure.

Triethylene glycol recovery by an energetically intensified thermosyphon-assisted falling film distillation unit: Experimental assessment on a pilot-scale unit and in-silico comparison with a conventional column from natural gas processing

Facing the emerging needs for energy-enhanced separation units, this work evaluated the triethylene glycol (TEG) regeneration, used as a dehydrating agent of natural gas from wells, by a novel thermosyphon-assisted falling film distillation technology, called Destubcal. The pilot-scale device has an innovative heat supply through a two-phase closed thermosyphon, which ensures a uniform energy distribution along the entire distillation tube. Based on current operating data from industrial water-rich TEG streams, different operating conditions were performed in the pilot-scale unit. The best recovery ratio (99.0%) was obtained with an evaporator temperature of 180 °C and a feed flow rate of 15 L/h. However, in order to maximize the bottom TEG composition, the best experimental condition achieved was 17 L/h and bottom temperature of 152.07 °C, due to an evaporator temperature of 170 °C. As a result, the Destubcal unit saved around 38.4% in energy requirement and reduced 49% the column height when compared to a conventional distillation column for the same recovery degree. Therefore, the proposed Destubcal technology can be considered a feasible alternative as recovery column for TEG regeneration in natural gas beneficiation units, with advantages of reduced dimensions and energy-saving operation.

Ultrasensitive fluorescence detection of microRNA through DNA-induced assembly of carbon dots on gold nanoparticles with no signal amplification strategy.

An ultrasensitive fluorescence assay strategy on the basis of carbon dots (CDs) and cDNA-modified gold nanoparticles (AuNP-cDNA) was developed for the determination of microRNA-21 (miRNA-21) via internal filtering effect (IFE). Positively charged CDs (PEI-CDs), the fluorophores in IFE, were synthesized via a hydrothermal method using polyethyleneimine (PEI) as surface ligand. The maximum emission wavelength is located at 500 nm under the excitation of 410 nm. AuNPs, the absorbers, were modified with single-stranded DNA (cDNA), which is completely complementary to miRNA-21. The fluorescence of PEI-CDs is quenched due to the assembly of PEI-CDs and AuNPs-cDNA. In the presence of miRNA-21, the hybridization between miRNA-21 and cDNA causes the release of PEI-CDs and the recovery of fluorescence intensity.The fluorescence recovery degree is linearly correlated with the logarithm of miRNA-21 concentration in the range of 1-1000 fM. This method can be applied to determine miRNA-21 in real serum samples, and the detection results are in well agreement with those of qRT-PCR. The determination of miRNA-21spiked into diluted human serum samples displays satisfactory recovery within the range88.44-112.7%, which confirmed the reliability for miRNAs detection in real samples.