Comprehensively evaluating the relationships between marital status and other family factors with cardiovascular disease and long-term overall mortality in the elderly: a study of 48 510 Chinese individuals.

BACKGROUND: Marital status is associated with cardiovascular disease (CVD) incidence and overall mortality, yet limited research on this topic in elderly individuals is available. Our aim was to comprehensively assess the impact of marital status and other family factors on CVD incidence and long-term mortality among elderly people. METHODS: Data from the Chinese Longitudinal Healthy Longevity Survey (2002/2005/2008-2018) for participants aged ≥60 years were analysed. A cross-sectional study initially examined the correlation between spouses, offspring, living arrangements, and CVD using logistic regression. Subsequently, a retrospective cohort study investigated the long-term associations of these factors with overall mortality via Kaplan-Meier and Cox regression analyses. RESULTS: The study involved 48 510 subjects (average age: 87 years). The cross-sectional analysis revealed a correlation between living with a spouse and an increased incidence of heart disease (adjusted OR 1.27, 95% CI 1.04-1.55) and cerebrovascular disease/stroke (adjusted OR 1.26, 95% CI 1.11-1.42). According to the retrospective cohort analysis, living with a spouse significantly reduced overall mortality (adjusted HR 0.84, 95% CI 0.80-0.87), irrespective of marital relationship quality. Conversely, living with offspring (adjusted HR 1.12, 95% CI 1.08-1.16), having more children (adjusted Pnonlinearity = 0.427) or cohabitants (adjusted Pnonlinearity < 0.0001) were associated with increased overall mortality. CONCLUSION: In the elderly population, being married and living with a spouse were not significantly associated with a decrease in CVD incidence but were associated with a reduction in long-term overall mortality. Living with offspring, having more children, or having a larger family size did not replicate the protective effect but indicated greater overall mortality.

The management of non-culprit vessel(s) in patients with unstable angina/non-ST elevation myocardial infarction and chronic kidney dysfunction.

BACKGROUND AND AIMS: The clinical effects of multivessel interventions in patients with unstable angina/non-ST-segment elevation myocardial infarction (UA/NSTEMI), multivessel disease (MVD) and chronic kidney disease (CKD) remain uncertain. This study aimed to investigate the safety and effectiveness of intervention in non-culprit lession(s) among this cohort. METHODS: We consecutively included patients diagnosed with UA/NSTEMI, MVD and CKD between January 2008 and December 2018 at our centre. After successful percutaneous coronary intervention (PCI), we compared 48-month overall mortality between those undergoing multivessel PCI (MV-PCI) through a single-procedure or staged-procedure approach and culprit vessel-only PCI (CV-PCI) after 1:1 propensity score matching. We conducted stratified analyses and tests for interaction to investigate the modifying effects of critical covariates. Additionally, we recorded the incidence of contrast-induced nephropathy (CIN) to assess the perioperative safety of the two treatment strategies. RESULTS: Of the 749 eligible patients, 271 pairs were successfully matched. Those undergoing MV-PCI had reduced all-cause mortality (hazard ratio (HR): 0.67, 95% confidence interval (CI): 0.48-0.67). Subgroup analysis showed that those with advanced CKD (estimated glomerular filtration rate (eGFR) ≤ 30 mL/min/1.73 m2 ) could not benefit from MV-PCI (P = 0.250), and the survival advantage also tended to diminish in diabetes (P interaction < 0.01; HR = 0.95, 95% CI = 0.65-1.45). Although the staged-procedure approach (N = 157) failed to bring additional survival benefits compared to single-procedure MV-PCI (N = 290) (P = 0.460), it showed a tendency to decrease the death risk. CIN risks in MV-PCI and CV-PCI groups were not significantly different (risk ratio = 1.60, 95% CI = 0.94-2.73). CONCLUSION: Among patients with UA/NSTEMI and non-diabetic CKD and an eGFR > 30 mL/min/1.73 m2 , MV-PCI was associated with a reduced risk of long-term death but did not increase the incidence of CIN during the management of MVD compared to CV-PCI. And staged procedures might be a preferable option over single-procedure MV-PCI.

Simulation Study on Molecular Behavior of Rhamnolipids and Biobased Zwitterionic Surfactants at the Oil/Water Interface: Effect of Rhamnose Moiety Structures.

Molecular behavior of rhamnolipid mixed with a biobased zwitterionic surfactant at an n-hexadecane/water interface has been studied, and the effects of a rhamnose moiety and composition are evaluated. Results showed that rhamnolipid abundantly interacts with biobased surfactant EAB by means of hydrophobic interactions between aliphatic tails and electrostatic interactions between headgroups, including the attractive interaction between COO- of rhamnolipids and N+ of biobased surfactants and the repulsive interaction between COO- of both surfactants. Dirhamnolipid has a larger number of bound Na+ and a more stable bound structure of COO- ∼ Na+, which screens the repulsive interaction between two kinds of surfactants and shows a more homogeneous distribution with biobased surfactants. The interfacial tension between n-hexadecane and water has been synergistically reduced by dirhamnolipids mixed with biobased surfactants at a higher molar ratio of biobased surfactants. Monorhamnolipids show a strengthened interaction with N+ of biobased surfactants and a more stable hydrogen bond with water relative to that of dirhamnolipids, and there is no synergistic effect in lowering the interfacial tension for the mixture of monorhamnolipids and biobased surfactants. The present work provides details of the molecular behavior of biosurfactant rhamnolipids mixed with biobased surfactants and obtains the key factor in affecting the interfacial properties of the binary system.

Allopurinol for Secondary Prevention in Patients with Cardiovascular Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

BACKGROUND: The effects of allopurinol in patients with cardiovascular disease are not well defined; therefore, the latest evidence is summarized in this study. METHODS: PubMed, Embase, Cochrane Library, and ClinicalTrials.gov databases were searched for randomized controlled trials (RCTs) of allopurinol in patients with cardiovascular disease published up to 11 February 2023. The primary outcome was cardiovascular death. RESULTS: We combined the results of 21 RCTs that included 22,806 patients. Compared to placebo/usual care, allopurinol treatment was not associated with a significant reduction in cardiovascular death (RR 0.60; 95% CI 0.33-1.11) or all-cause death (RR 0.90; 95% CI 0.72-1.12). However, evidence from earlier trials and studies with small sample sizes indicated that allopurinol might confer a protective effect in decreasing cardiovascular death (RR 0.34; 95% CI 0.15-0.76) across patients undergoing coronary artery bypass grafting (CABG) or having acute coronary syndrome (ACS). In comparisons between allopurinol and febuxostat, we observed no difference in cardiovascular death (RR 0.92; 95% CI 0.69-1.24) or all-cause death (RR 1.02; 95% CI 0.75-1.38). CONCLUSION: Allopurinol could not reduce cardiovascular (CV) death or major adverse CV outcomes significantly in patients with existing cardiovascular diseases. Given the limitations of the original studies, the potential advantages of allopurinol observed in patients undergoing CABG or presenting with ACS necessitate further confirmation through subsequent RCTs. In the comparisons between allopurinol and febuxostat, our analysis failed to uncover any marked superiority of allopurinol in reducing the risk of adverse cardiovascular incidents.

Difference in Step-Wise Production Rules of SP Binary Flooding for Conglomerate Reservoirs with Different Lithologies.

The purpose of this study is to clarify the difference in oil production rules of conglomerate reservoirs with different pore structures during surfactant-polymer (SP) binary flooding and to ensure the efficient development of conglomerate reservoirs. In this paper, the full-diameter natural cores from the conglomerate reservoir of the Triassic Kexia Formation in the seventh middle block of the Karamay Oilfield (Xinjiang, China) are selected as the research objects. Two schemes of single constant viscosity (SCV) and echelon viscosity reducing (EVR) are designed to displace oil from three main oil-bearing lithologies, namely fine conglomerate, glutenite, and sandstone. Through comprehensive analysis of parameters, such as oil recovery rate, water content, and injection pressure difference, the influence of lithology on the enhanced oil recovery (EOR) of the EVR scheme is determined, which in turn reveals the differences in the step-wise oil production rules of the three lithologies. The experimental results show that for the three lithological reservoirs, the oil displacement effect of the EVR scheme is better than that of the SCV scheme, and the differences in recovery rates between the two schemes are 9.91% for the fine conglomerate, 6.77% for glutenite, and 6.69% for sandstone. By reducing the molecular weight and viscosity of the SP binary system, the SCV scheme achieves the reconstruction of the pressure field and the redistribution of seepage paths of chemical micelles with different sizes, thus, achieving the step-wise production of crude oil in different scale pore throats and enhancing the overall recovery of the reservoir. The sedimentary environment and diagenesis of the three types of lithologies differ greatly, resulting in diverse microscopic pore structures and differential seepage paths and displace rules of SP binary solutions, ultimately leading to large differences in the enhanced oil recoveries of different lithologies. The fine conglomerate reservoir has the strongest anisotropy, the worst pore throat connectivity, and the lowest water flooding recovery rate. Since the fine conglomerate reservoir has the strongest anisotropy, the worst pore throats connectivity, and the lowest water flooding recovery, the EVR scheme shows a good "water control and oil enhancement" development feature and the best step-wise oil production effect. The oil recovery rate of the two schemes for fine conglomerate shows a difference of 10.14%, followed by 6.36% for glutenite and 5.10% for sandstone. In addition, the EOR of fine conglomerate maintains a high upward trend throughout the chemical flooding, indicating that the swept volume of small pore throats gradually expands and the producing degree of the remaining oil in it gradually increases. Therefore, the fine conglomerate is the most suitable lithology for the SCV scheme among the three lithologies of the conglomerate reservoirs.

Adaptive control for downhole nuclear magnetic resonance excitation.

Nuclear magnetic resonance (NMR) measurements are performed with the pulse sequence and acquisition parameters set by the operator, which cannot be adjusted in real time according to sample characteristics. In one acquisition cycle, usually thousands of high-power pulses are transmitted and thousands of echo points are acquired. The power consumption cause the RF amplifier to overheat, and large amounts of acquired data may be invalid. Therefore, the optimization of excitation and acquisition processes is necessary to improve measurement efficiency. We explore a scheme for the real-time measurement of the samples by adaptively regulating the pulse sequence, which adapts the variable TE pulse sequence as the reconnaissance mode. The appropriate pulse sequence and reasonable parameters (NE, TE) can be selected according to the relaxation characteristics of the samples.This adaptive control strategy has great significance in guiding both dynamic and static measurements, and it is especially suitable for occasions where low magnetic field gradients and diffusion terms can be ignored. We also design a test circuit for adaptive control, which has the function of automatic parameter adjustment. By adjusting parameters such as the number of refocusing pulses, echo spacing, etc., the effective measurement of the samples can be achieved in practice.

A study on multi-exponential inversion of nuclear magnetic resonance relaxation data using deep learning.

Nuclear magnetic resonance (NMR) is a powerful tool for formation evaluation in the oil industry to determine parameters, such as pore structure, fluid saturation, and permeability of porous materials, which are critical to reservoir engineering. The inversion of the measured relaxation data is an ill-posed problem and may lead to deviations of inversion results, which may degrade the accuracy of further data analysis and evaluation. This paper proposes a deep learning method for multi-exponential inversion of NMR relaxation data to improve accuracy. Simulated NMR data are first constructed using a priori knowledge based on the signal parameters and Gaussian distribution. These data are then used to train the neural network designed to consider noise characteristics, signal decay characteristics, signal energy variations, and non-negative features of the T2 spectra. With the validation from simulated data, the models introduced by multi-scale convolutional neural network (CNN) and attention mechanism outperform other approaches in terms of denoising and T2 inversion. Finally, NMR measurements of rock cores are used to compare the effectiveness of the attention multi-scale convolutional neural network (ATT-CNN) model in practical applications. The results demonstrate that the proposed method based on deep learning has better performance than the regularization method.

In situ micro-emulsification during surfactant enhanced oil recovery: A microfluidic study.

HYPOTHESIS: It is generally believed that the improved efficiency of surfactant enhanced oil recovery (EOR) comes from ultra-low interfacial tension (IFT) between oil and surfactant solution owing to the formation of middle-phase microemulsion. However, hindered visibility in underground porous media prevents direct observation of in situ generation of middle-phase microemulsion during surfactant flooding. Thus, direct visualization of the process is vital, and could clarify its contribution to EOR. EXPERIMENTS: Micro-emulsification of a displacing fluid containing sodium 4-dodecylbenzenesulfonate and alcohol propoxy sulfate with model oil was investigated. Phase diagrams were drawn using salinity scans, and the influence of polymer on emulsification was analyzed. Micro-emulsification was monitored through in situ fluorescent tagging via 2D-microfluidics and ex situ visualization via cryo-electron microscopy and small angle X-ray scattering. Its contribution to the oil recovery factor was quantified by measuring the volume of each phase in the eluates. FINDINGS: On-chip experiments indicated that in situ micro-emulsification occurred when the prescreened surfactant solution flowed in contact with trapped oil. The aqueous phase initially invaded the residual oil, forming a low mobility microemulsion. This microemulsion was then diluted by subsequent displacing fluid, forming a new driving fluid that caused ultra-low IFT in the trapped oil downstream. Under the synergistic effect of micellar solubilization and trapped-oil mobilization, the recovery factor could be increased by up to 40% over waterflooding and 43% on polymer inclusion in the formulation.

Antidyslipidemia Pharmacotherapy in Chronic Kidney Disease: A Systematic Review and Bayesian Network Meta-Analysis.

BACKGROUND AND AIMS: The benefits and safety of antidyslipidemia pharmacotherapy in patients with chronic kidney disease were not well defined so the latest evidence was summarized by this work. METHODS: This systematic review and Bayesian network meta-analysis (NMA) included searches of PubMed, Embase, and Cochrane Library from inception to 28 February 2022, for randomized controlled trials of any antilipidaemic medications administered to adults with chronic kidney disease [CKD: defined as estimated glomerular filtration rate (eGFR) ≤ 60 mL/min/1.73 m2 not undergoing transplantation], using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) tool to assess the certainty of the evidence. RESULTS: 55 trials and 30 works of them were included in our systematic review and NMA, respectively. In comparisons with no antidyslipidemia therapy or placebo, proprotein convertase subtilisin/Kexin type 9 inhibitors plus statin (PS) was the most effective drug regimen for reducing all-cause mortality (OR 0.62, 95% CI [0.40, 0.93]; GRADE: moderate), followed by moderate-high intensity statin (HS, OR 0.76, 95% CI [0.60, 0.93]; I2 = 66.9%; GRADE: moderate). PS, HS, low-moderate statin (LS), ezetimibe plus statin (ES), and fibrates (F) significantly decreased the composite cardiovascular events. The subgroup analysis revealed the null effect of statins on death (OR 0.92, 95% CI [0.81, 1.04]) and composite cardiovascular events (OR 0.94, 95% CI [0.82, 1.07]) in dialysis patients. CONCLUSION: In nondialysis CKD patients, statin-based therapies could significantly and safely reduce all-cause death and major composite cardiovascular events despite the presence of arteriosclerotic cardiovascular disease and LDL-c levels. Aggressive medication regimens, PS and HS, appeared to be more effective, especially in patients with established CAD.

13C Solid-State NMR Analysis of the Chemical Structure in Petroleum Coke during Idealized In Situ Combustion Conditions.

Petroleum cokes with different chemical structures and oxygen-containing functional groups were obtained from two kinds of naphthenic- and paraffin-base crude oils by simulating an in situ combustion (ISC) process with the same reaction atmosphere and different reaction temperatures. 13C wide-cavity solid-state nuclear magnetic resonance (13C NMR) spectroscopy was used to identify and investigate the oxygen-containing functional groups of petroleum cokes obtained under different compositions and reaction temperatures. This study demonstrated that with the increase of coking temperature, the content of alkyl side chain and active oxygen-containing functional groups in naphthenic-base crude coke decreased obviously, while the content of aromatic carbon increased. The 13C NMR analysis of the two kinds of petroleum cokes obtained at 500 °C further revealed that the paraffin-base petroleum coke retained a high content of oxygen- and nitrogen-rich functional groups, while the naphthenic-base petroleum coke had a lower amount of carbonyl groups and oxygen-containing functional groups.

Borehole Nuclear Magnetic Resonance Study at the China University of Petroleum.

The research of borehole nuclear magnetic resonance (NMR) began in the 1950 s, but the maturity and large-scale applications of relevant instruments started in the mid-1990. To date, borehole NMR is an important means for borehole in-situ analysis and oil and gas evaluation, which significantly improves the success rate of exploration and the evaluation accuracy of oil and gas reservoirs. Its development has also contributed importantly to low-field and industrial NMR theories and experimental methodologies. Companies and individuals in the United States, China and other countries have developed the capabilities to engineer and deploy borehole NMR instruments and measurements independently. NMR imaging and evaluation of heterogeneous reservoirs and unconventional oil and gas are worldwide problems, involving the innovation of borehole NMR and the advanced manufacture of instruments and equipment. The commercial technology of borehole oil and gas exploration is highly competitive and proprietary. It is difficult to gain full insight into the details of the technologies and development from published literatures. Based on the research of the author's NMR laboratory at the China University of Petroleum (CUP), this paper reviews the core technologies of borehole NMR and its applications, discusses selected important issues that have not been fully solved, and looks forward to the direction and prospects of future development.

Revascularization vs. Conservative Medical Treatment in Patients With Chronic Kidney Disease and Coronary Artery Disease: A Meta-Analysis.

BACKGROUND: As a strong risk factor for coronary artery disease (CAD), chronic kidney disease (CKD) indicates higher mortality in patients with CAD. However, the optimal treatment for the patients with two coexisting diseases is still not well defined. METHODS: To conduct a meta-analysis, PubMed, Embase, and the Cochrane database were searched for studies comparing medical treatment (MT) and revascularization [percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG)] in adults with CAD and CKD. Long-term all-cause mortality was evaluated, and subgroup analyses were performed. RESULTS: A total of 13 trials met our selection criteria. Long-term (with at least a 1-year follow-up) mortality was significantly lower in the revascularization arm [relative risk (RR) = 0.66; 95% CI = 0.60-0.72] by either PCI (RR = 0.61; 95% CI = 0.55-0.68) or CABG (RR = 0.62; 95% CI = 0.46-0.84). The results were consistent in dialysis patients (RR = 0.68; 95% CI = 0.59-0.79), patients with stable CAD (RR = 0.75; 95% CI = 0.61-0.92), patients with acute coronary syndrome (RR = 0.62; 95% CI = 0.58-0.66), and geriatric patients (RR = 0.57; 95% CI = 0.54-0.61). CONCLUSION: In patients with CKD and CAD, revascularization is more effective in reducing mortality than MT alone. This observed benefit is consistent in patients with stable CAD and elderly patients. However, future randomized controlled trials (RCTs) are required to confirm these findings.

Design of a new LWD NMR tool with high mechanical reliability.

Nuclear magnetic resonance (NMR) provides useful information for formation evaluation on pore size and pore volume. Depending on field operations, there are two types of borehole NMR: wireline logging and logging-while-drilling (LWD). The latter type is more convenient. But due to the high mechanical failure risk caused by insufficient mechanical strength of the tool and vibrations during measurement, the quality of LWD NMR measurements are severely affected. In this paper, to enable high reliability and vibration tolerance, we propose a new design and implement a new LWD NMR tool, whose features includes a double hollow cylindric magnet (DHCM) structure and a solenoid-optimized antenna. The DHCM structure greatly reduces the proportion of the magnet in the cross-section of the tool without reducing B0 field strength. Thus, the mechanical strength and the reliability of the tool is greatly improved. The antenna is improved by optimizing the parameters of each coil of the solenoid for finding the generated B1 distribution best matching B0. The new design has a saddle sensing area in the axial and radial plane with a width greater than 50 mm, which is wide enough to ensure the validity of the T2 measurement under strong vibrations. We had demonstrated that this new tool performs well when TE = 0.6 ms, ensuring the measurement richness is suitable for LWD prospecting for unconventional oil and gas reservoirs. Besides, this design is suitable for that in slim holes.

Visualizing in-situ emulsification in porous media during surfactant flooding: A microfluidic study.

HYPOTHESIS: It is well recognized that crude oil could be emulsified during surfactant flooding process, and recently such an in-situ emulsification was found practically helpful for enhanced oil recovery (EOR). However, no direct proofs are reported yet to unravel how emulsion is formed in porous media and how important to increasing oil recovery factor due to unavailability to visualize the emulsification process, thus it is desirable to verify visibly the formation of emulsion in porous media and the contribution of emulsification to EOR process. EXPERIMENTS: Two types of microfluidic chips with heterogeneous and homogeneous pore geometries respectively were employed to simulate the underground oil reservoir environment. Sodium dodecylbenzenesulfonate (SDBS) was selected as a model surfactant, and its aqueous solution was injected into the paraffin oil-saturated microchip to mimic the displacing process. A series of tests were conducted by varying SDBS concentration, electrolyte content, injection rate, and pore-scale snapshots were captured for qualitative and quantitative analysis of in-situ emulsification during the surfactant flooding. FINDINGS: Both oil-in-water (O/W) and water-in-oil (W/O) emulsions are formed in microchips during the surfactant flooding. Increasing SDBS concentration, migration distance, injection rate, or addition of electrolyte tends to form smaller O/W particles through snapping action at pore throat, and vice versa. Smaller size endows oil with a better mobility to go through the pore throat, and up to 24% extra emulsion can be achieved through emulsification entrainment; bigger droplets can block the dominant paths, thus improving sweep efficiency and increasing oil recovery factor up to 30% compared to waterflooding. Furthermore, W/O emulsification was found to be a time-dependent process influenced by SDBS concentration, and oil was recovered by diffusing surfactant solution into oil phase and replacing the oil-occupied space in porous media.

Inside-out azimuthally selective NMR tool using array coil and capacitive decoupling.

Inside-out nuclear magnetic resonance (NMR) is a unique technique for investigating large in-situ objects outside of tools, to provide pore structure and pore-bearing fluids properties. However, in borehole, objects towards azimuthal orientations pose different properties, referred to as azimuthal spatial heterogeneity. This may lead to ambiguous evaluations by utilizing present inside-out NMR measurement, which hardly resolves azimuthal information and loses the location information of oil/gas. In this paper, we for the first time design and construct an innovative tool to investigate the heterogeneity of large in-situ samples. The most key component, array coil, which performs with azimuthal selection, measurement consistency and interactive isolation, configured in this novel tool to capture heterogeneity information. Whereas, strong coupling between neighboring coil elements largely decrease the coil sensitivity. Capacitive decoupling network is bridged into adjacent ports without segmenting coils to be decoupled and could be easily adjusted by electrical relays. The coil model and numerical simulation are firstly given to demonstrate the array coil configuration, B1 field map and mutual coupling effects on coil sensitivity. Capacitive network is then introduced to be theoretically and practically analyzed to minimize coupling effects. Simulation and experimental results demonstrate that these coil elements have excellent consistency and independence to feasibly acquire the azimuthal NMR data.

Oil solubilization in sodium dodecylbenzenesulfonate micelles: New insights into surfactant enhanced oil recovery.

HYPOTHESIS: The current mechanism of surfactant enhanced oil recovery (EOR) mainly relies on forming middle-phase microemulsions to get ultra-low oil-water interfacial tension. However, residual oil can also be recovered using low concentration surfactant solutions without microemulsion formation, and the interaction between the surfactant solution and crude oil at very early contact has not been studied yet. We hypothesize micelle solubilization of oil as an alternative EOR mechanism. EXPERIMENTS: Sodium dodecylbenzenesulfonate (SDBS), anisole and 1-hexene were used as a model surfactant and model polar and nonpolar compounds in crude oil, respectively. The interaction between SDBS micelles and these two additives was investigated with dynamic light scattering, UV-Vis spectroscopy, 1H NMR spectroscopy, cryogenic transmission electron microscopy, confocal microscope and small angle neutron scattering. FINDINGS: SDBS micelles become larger upon increasing additive concentration to transfer into swollen micelles. 1-Hexene is localized in the micelle core, and retains the spherical micelle shape, while anisole resides in the palisade layer and weakens the electrostatic repulsions among surfactant headgroups, inducing a sphere-rod transition. No emulsion droplets were observed for 0.2 wt% SDBS solution until 1.5 wt% anisole or 1-hexene was introduced. These findings help understanding the role surfactant micelles in EOR and propose a new mechanism for surfactant EOR processes.

A novel two-dimensional NMR relaxometry pulse sequence for petrophysical characterization of shale at low field.

Low field two-dimensional nuclear magnetic resonance (2D-NMR) relaxometry is a powerful probe for the characterization of heterogenous, porous media and provides geometrical, physical and chemical information about samples at a molecular level and has been widely used in shale studies. However, NMR signals of shale decay so rapidly, dry sample for particular, that the conventional two-dimensional pulse sequence is either not sensitive enough to short relaxation components or takes too much measurement time. In this paper, 2D-NMR relaxometry correlation based on partial inversion recovery CPMG (PIR-CPMG) pulse sequence is proposed and illustrated to improve the contrast over saturation recovery CPMG (SR-CPMG) and reduces the T1 encoding time of inversion recovery CPMG (IR-CPMG) for petrophysical characterization of shale. Subsequently, the kernel function and inversion method of this sequence are presented and the reliability of the inversion method is testified by numerical simulation. Next, theoretical analysis is conducted to validate the advantages of PIR-CPMG. Ultimately, experiments on copper sulfate solution, artificial sandstone, and shale samples are performed, respectively, to verify the feasibility and effectiveness of the proposed pulse sequence. The results demonstrate that the PIR-CPMG sequence is time-saving and high-contrast, especially for the short relaxation components. This pulse sequence can be utilized in bench-top NMR core analyzer and downhole well logging, potentially, to achieve integrated petrophysical characterization of shale.

Micellar Aggregation Behavior of Alkylaryl Sulfonate Surfactants for Enhanced Oil Recovery.

Alkylaryl sulfonate is a typical family of surfactants used for chemically enhanced oil recovery (EOR). While it has been widely used in surfactant-polymer flooding at Karamay Oilfield (40 °C, salinity 14,000 mg/L), its aggregation behavior in aqueous solutions and the contribution of aggregation to EOR have not been investigated so far. In this study, raw naphthenic arylsulfonate (NAS) and its purified derivatives, alkylaryl monosulfonate (AMS) and alkylaryl disulfonate (ADS), were examined under simulated temperature and salinity environment of Karamay reservoirs for their micellar aggregation behavior through measuring surface tension, micellar size, and micellar aggregation number. It was found that all three alkylaryl sulfonate surfactants could significantly lower the surface tension of their aqueous solutions. Also, it has been noted that an elevation both in temperature and salinity reduced the surface tension and critical micellar concentration. The results promote understanding of the performance of NAS and screening surfactants in EOR.

NMR characterizing mixed wettability under intermediate-wet condition.

Applying the concept of effective relaxivity to characterize wettability is based on the configuration of fluid distributions in porous media. However, in mixed-wet porous media with intermediate-wet patches (homogeneous wetting region), effective surface relaxivity cannot fully characterize wettability because fluid distributions are not directly corresponding to wetting patch distributions. Patches with different wettability interact with the same fluid differently, which leads to different surface relaxivity. The distribution of this kind surface relaxivity from porous media saturated with single fluid matches mixed wettability distribution. Here, we apply decay due to diffusion in internal field plus Carr-Purcell-Meiboom-Gill (DDIF-CPMG) method to obtain T2 and the pore size distribution correlation. The variation of surface relaxivity obtained from the correlation map is used to characterize wettability distributions of mixed-wet porous media. In this paper, we also redefine a parameter based on surface relaxivity distribution to evaluate mixed wettability under intermediate-wet condition. The experiment results with limestones show that, after wettability alteration of the sample, the distribution of the surface relaxivity is changed and closely correlated with pore size distribution, which demonstrates the features of mixed wettability under intermediate-wet conditions.

The downhole circumferential scanning magnetic resonance imaging tool.

The downhole circumferential scanning magnetic resonance logging is able to image saturation distribution and fluid properties of stratum around a borehole, thus providing relevant and abundant information for formation evaluation. The device employs a phase-controlled excitation device based on combined array structure to accomplish three dimensional data acquisition from axial, radial and circumferential directions. This paper focuses on the design principle of device and the structure of electronic control system. A mutual coupling analysis with array antenna was carried out using inductance coupling principle, and realize the decoupling and energy discharge compensation of array antennas. The circumferential scanning nuclear magnetic resonance technique has a potential of overcoming the weakness of two dimensional measurements and raising new applications that it determines the azimuth of the fluid in the borehole and realizes the imaging measurement of the pore structure and the reservoir fluid.