Optimizing acid microemulsions for cleaner gas production: A study on enhanced adsorption characteristics and implications in retardation.

The ultralow interfacial tension between the oil and aqueous phases and the solubilization characteristics in microemulsion systems make them useful for surface cleaning and enhanced oil recovery applications. Microemulsions can form an adsorbed barrier on rock, reducing the acid-rock reaction rate. However, as acid retardation additives, the adsorption patterns of microemulsions are not clearly defined. In this study, microemulsions composed of various electrical surfactants, oil cores, and oil core additives were obtained, and their phase behaviors were investigated. Through adsorption and reaction experiments, cleaning microemulsions that enhance adsorption effects were identified, and their adsorption patterns and adaptability under flow conditions were evaluated. The results demonstrate that incorporating negatively charged polar compounds forms an enhanced adsorption microemulsion characterized by an average droplet size of less than 30 nm after mixing with the acid. The introduction of negatively charged polar compounds resulted in a 177 % increase in adsorption and an 81 % improvement in static retardation effect. Dynamic adsorption tests indicate that the pseudo-second-order model more accurately describes the kinetics of dynamic adsorption of microemulsions on rock surfaces. Under a fixed flow rate, the dynamic retardation rate increased with the concentration of the microemulsion. In practical acidification, the adsorption of microemulsions results mainly from combined electrostatic forces and fluid scouring, characterized by a continuous process of adsorption and desorption. Scanning electron microscope also confirmed that microemulsions can form an adsorptive film on the rock, reducing the acid-rock reaction rate. This study offers practical guidelines for the selection and application of retardation additives, aiming to enhance the ecological compatibility of chemical treatments in low-permeability limestone reservoirs.

High-Temperature-Resistant Profile Control System Formed by Hydrolyzed Polyacrylamide and Water-Soluble Phenol-Formaldehyde Resin.

To realize the effective profile control of a heavy oil reservoir, hydrolyzed polyacrylamide (HPAM) and water-soluble phenol-formaldehyde resin (PR) were chosen to prepare the profile control system, which gelled at medium or low temperatures and existed stably at high temperatures in the meantime. The effects of phenolic ratios, PR concentration, and HPAM concentration on the formation and strength of the gels were systematically studied by the gel-strength code method and rheological measurements. And the microstructure of the gels was investigated by scanning electron microscope measurements. The results showed that the gelling time of the HPAM-PR system was 13 h at 70 °C. The formed gel could stay stable for 90 days at 140 °C. In addition, the gels showed viscoelastic properties, and the viscosity reached 18,000 mPa·s under a 1.5 s-1 shearing rate due to their three-dimensional cellular network structure. The formation of the gels was attributable to the hydroxyl groups of the PR crosslinking agent, which could undergo the dehydration condensation reaction with amide groups under non-acidic conditions and form intermolecular crosslinking with HPAM molecules. And the organic crosslinker gel system could maintain stability at higher temperatures because covalent bonds formed between molecules.

Preparation and Performance Study of Microemulsion Acid for Comprehensive Plugging Removal in Carbonate Reservoir.

Matrix acidification is one of the most effective stimulations to dissolve scales and remove damage in carbonate reservoirs. However, existing acid systems are difficult to dissolve organic and inorganic scales simultaneously, and complex multi-stage alternative injection often introduces new precipitation and damages the reservoir. Here, based on the retardation ability of emulsified acid and the stable structure of microemulsion, an oil-phase solvent was preferably selected, and the surfactant and cosurfactant were optimized to prepare an acid-in-oil type microemulsion acid capable of dissolving both organic and inorganic scales and high solubilizing for hydrochloric acid. Based on the rotating disc experiment, scale dissolution experiment and acid driving experiment, the acid-rock reaction kinetics, scale dissolution ability and acidizing and plugging removal performance of microemulsion acid in a carbonate reservoir were systematically studied and compared. The results show that Solvesso 150 (aromatic solvent) has the advantages of low toxicity, high flash point and high-scale dissolving ability. At NP-4: OP-10: A (cosurfactant) = 3:3:4, the microemulsion acid system has the strongest ability to solubilize hydrochloric acid and can solve the problem of low H+ concentration. The particle size of microemulsion acid is smaller compared to emulsified acid. At 60 °C, the mass transfer coefficient of microemulsion acid is 3.2 × 10-8 cm2/s, which is one order of magnitude less than that of emulsified acid. Microemulsion acid shows good solubility performance in dissolving organic and inorganic scales, and the comprehensive solubility of mixed scales can reach 98.28%. The stronger scale solubilization ability and lower acid-rock reaction rate enable microemulsion acid to form a thin and straight main wormhole, thus enhancing the acidizing and plugging removal effect. This study can solve the problem of poor hydrochloric acid solubilization ability of microemulsion acid to a certain extent, which provides theoretical and data support for the research and development of microemulsion acid and the efficient plugging removal technology for carbonate reservoirs.

Experimental Study on Plugging Behavior of Degradable Diverters in Partially Open Fracture in Temporary Plugging and Diverting Fracturing.

Temporary plugging and diverting fracturing technology (TPDF) has been successfully applied to improve reservoir productivity. In real reservoirs, a considerable number of fractures have relatively rapidly decreasing fracture widths and closed ends. However, the plugging behavior of diverters in this typical fracture called the partially open fracture (POF) is still unclear because of the few related studies. This paper aims to investigate the plugging behavior of diverters at the fracture tip. The 3D-printed fracture model was used to reproduce the partially open fracture, and the morphological characteristics of the partially open fracture and the open fracture were compared based on the scan data. A series of plugging experiments were conducted to monitor the transport behavior of the diverter in partially open fractures through multiple pressure sensors on the fracture model and to investigate the influence of diverter formula and fracture type on plugging behavior. Finally, based on the experimental results, the plugging mechanism of diverters in partially open fractures was analyzed. The plugging experiments show that a higher-pressure distribution appears at the fracture tip when using a combination of fibers and particles, indicating that it is beneficial for the diverter to transport to the tip and form plugging in the fracture, and it should be noted that small changes in particle size and concentration had a significant influence on the plugging performance. Therefore, it is recommended to use a combination of fibers and particles of multiple sizes (maximum particle size not exceeding half of the fracture width) to achieve a better plugging effect. In addition, the plugging behaviors of partially open fractures and open fractures are different. For partially open fractures with widths of 1, 2, and 4 mm, the recommended formula of the diverter is 1 wt % fibers + 1 wt % 0.15 mm particles, 1 wt % fibers + 1 wt % 0.15 mm particles + 1 wt % 1 mm particles, and 1 wt % fibers + 1 wt % 0.15 mm particles + 1 wt % 1 mm particles + 1 wt % 2 mm particles, respectively. The above experimental results provide an experimental and theoretical basis for the application of TPDF in the field.

Spectro-spatial analysis of elastic wave propagation in nonlinear elastic metamaterial systems with damping.

Different from the linear counterpart, elastic wave propagation in nonlinear elastic metamaterials with damping (EMD) systems has much more novel behaviors. It is little work that reveals the nonlinear wave propagation mechanism in the nonlinear EMD in the literature. In this paper, nonlinear EMD systems with different configurations for the nonlinear elements are constructed to study the nonlinear wave propagation characteristics based on the analytical formulation. Nonlinear wave propagation attenuation characteristics in nonlinear EMD systems are studied in the frequency-domain. Spectro-spatial characteristics of nonlinear traveling wave packet in space- and time-domain are also analyzed to reveal space frequency-domain characteristics. Influences of different configurations for the nonlinear elements on wave propagation in nonlinear EMD systems are discussed. Results shown that locations of band structures can be tuned by changing intensities of nonlinearities in the nonlinear EMD systems, which are not found in the linear system. Moreover, different configurations for the nonlinear elements can lead to localization feature emerged in a nonlinear EMD system, which indicates solitary waves causing from the interaction between dispersion and nonlinearity exist in the nonlinear systems. This interesting wave propagating properties can be used to design new devices for acoustic switches, energy harvesting, and broadband vibration control.

Optimization of Fracturing Fluid and Retarded Acid for Stimulating Tight Naturally Fractured Bedrock Reservoirs.

In tight naturally fractured bedrock reservoirs, hydrocarbons are typically stored in fractures, where hydraulic fracturing is needed to connect these fractures to the wellbore. The cross-linked gel is used as the fracturing fluid to reduce the fluid leak-off through natural fractures; however, it can cause formation damage due to its high content of residues after breaking. A synthetic polymer is introduced and evaluated that can maintain a high viscosity to minimize the leak-off , while having a low residue content after breaking. To further enhance the conductivity of the created fracture network, acid is applied to etch and roughen the created fracture faces. Because the target reservoir has a complex mineral composition, a three-step coreflood sequence using reservoir rock samples with controlled fracture widths is established to quantify the enhancement of different retarded acids and to reveal the mechanism behind it. The results indicate the synergy effect of reducing the acid concentration and surfactant adsorption on rock surfaces can lead to an obvious enhancement of the fracture permeability after acidizing, while the mud acid or hydrofluoric acid is not suitable for the target reservoir where concentrations of silicates and clays are relatively high.

Sports Economic Mining Algorithm Based on Association Analysis and Big Data Model.

With the implementation of national strategies such as sports power and national fitness, the sports economy has become an important element of high-quality national development, and the demand for sports economy and management talents is greatly increased. Particularly in the new area with big data as the typical feature, the teaching content, teaching method, and teaching mode of sports economics and management majors have put forward new requirements. The continuous progress of storage and network technology has prompted the generation of massive multisource spatiotemporal data in various fields. The advantage of association analysis algorithms is that they are easy to code and implement. The relationships found by association analysis can take two forms: frequent itemsets or association rules. We use correlation analysis methods to perform correlation learning between sports economy and related big data and thus improve the development of sports economy. Mining and analyzing the relevant big data can precisely reveal the problems of sports economic development and can realize the fine management of sports, thus contributing to the healthy development of sports. Mastering the skills of acquiring, analyzing, and applying big data is the core content of sports economic analysis. The sports economy has refined and intelligent management means, and its adoption of virtual reality reflects the current situation and development trend of the sports business, which further highlights the status and role of multisource big data in the sports economy. Based on these, this paper proposed a sports economy mining algorithm in view of the correlation analysis and big data model. Then, we verified the effectiveness of the model through experiments, which laid the foundation for the development of the sports economy.

Methods to Improve the Efficiency of Rural Physical Education Teaching Resources Allocation and Utilization in the Context of Artificial Intelligence.

School physical education is an important part of school education, and physical education resources are the overall measure of a school's physical education level. Rural schools are limited by environmental constraints, especially the lack of physical education resources verification. Therefore, the allocation and utilization efficiency improvement of rural physical education resources are an important element of rural physical education construction. With the mature development of artificial intelligence technology, it has great potential for application in the field of cultural education. Artificial intelligence technology has the advantages of ease of use, strong self-adaptation, and excellent generalization ability, and it is selected for data processing in this paper. Using artificial intelligence technology, the study of sports informatization to help rural sports development and rational utilization of resources can help rural sports education development, rural sports industry prosperity, rural sports talent revitalization, rural sports governance system improvement, and governance capacity enhancement. The artificial intelligence raindrop algorithm, which can automate the statistics of all relevant factors and derive results based on data fusion, was selected as the core algorithm of this paper. Therefore, this paper proposes an intelligent algorithm for allocating and improving the efficiency of rural sports teaching resources so as to improve the informatization level of the rural sports industry, promote industrial integration based on local needs, accelerate the "online urban-rural integration" in rural sports education, rural fitness guidance, and rural recreation and medical care, and rely on multiple entities. We will support the new model of sports informatization to empower rural sports teaching development by relying on the collaboration of multiple entities.

Prediction of Refracturing Effect of Tight Gas Reservoirs Based on Bayesian Inversion Algorithm.

As a key technology for tight gas stimulation, refracturing plays an important role in tight gas development. In the production process of tight gas wells, the reservoir or fracturing process may cause the hydraulic fractures to gradually fail and the production to continuously decrease. In order to restore the productivity of a single well, it is necessary to refract the well to reopen the failed fractures or fracturing. Reasonable refracturing timing and optimization of refract fracture parameters are important guarantees to ensure the benefits of refracturing in tight gas wells, and relevant research on it can provide theoretical and technical guidance for field construction design. Based on the inverse problem of the dynamic prediction model of tight gas well productivity, this paper proposes an inversion method of formation and fracture parameters before refracturing based on Bayesian inversion algorithm. Finally, based on the geology and development data of the fractured wells in the Sulige gas field, the field application of refracting well selection, determination of refracting reasonable timing, and prediction of refracting effect is carried out. The actual production data are compared, and it is shown that this method can provide theoretical guidance for high-efficiency production-increasing construction on-site.

High-Temperature-Resistant, Low-Concentration Water-Controlling Composite Cross-Linked Polyacrylamide Weak Gel System Prepared from Oilfield Sewage.

The polyacrylamide weak gel is an effective system to block a high-permeability layer, realize water control, and enhance oil recovery. However, its application is limited by poor temperature resistance and high polymer dosage. In this paper, an inorganic-organic composite cross-linking agent was synthesized by using Cr(III) and phenolic resin. The composite cross-linking agent can cross-link low concentrations of polyacrylamide to obtain a high-temperature-resistant weak gel system in oilfield sewage. By adjusting the ratio of Cr(III), phenolic resin, and polyacrylamide, an optimum formula MF-7 can be obtained according to the gel strength. Results from evaluation experiments show that the strength of MF-7 can reach H grade even at polyacrylamide concentrations as low as 0.3%. The temperature resistance of the weak gel system is up to 100 °C, and no syneresis occurs after 330 h at 95 °C. Scanning electron microscopy (SEM) results show that MF-7 has a three-dimensional network structure with spherical nodes. The spherical node is composed of polyacrylamide, and its structure size is completely matched with the hydrodynamic radius of the used polyacrylamide. When combined with the network structure formed by Cr(III), the dense cross-linking network structure with nodes can greatly improve the strength and thermal stability of the gel system. The higher the molecular weight of the polyacrylamide used, the higher the strength of the gel obtained. Overall, the composite cross-linking agent can synergistically improve the mechanical properties of the gel, and this weak gel system formed by oilfield sewage is more economical and tolerant.

Experimental Investigation on the Fracture Conductivity Behavior of Quartz Sand and Ceramic Mixed Proppants.

In this paper, a series of fracture conductivity experiments were designed and conducted by an American Petroleum Institute (API) standard fracture conductivity evaluation system. The mixing proportion of quartz sand and ceramic was optimized. By the evaluation of the proppant breakage rate and sphericity analysis of mixed proppant with different sand volume proportions (P S), the proppant mixture conductivity evolution behavior was analyzed. Results of this study showed that the conductivity of mixed proppant was between that of pure ceramic proppant and pure quartz sand proppant under the same conditions. For 20/40 mesh mixed proppant, a small amount of ceramic (25%) in mixed proppant could obtain 1.27-3 times higher conductivity than pure sand, while 40/70 mesh mixed proppant required the addition of 50% or more ceramic. The crushing resistance of mixed proppant determined the decrease of conductivity with the increase of effective closure stresses. A logarithmic empirical model was further derived from the results, which could be used to forecast the performance of fracture conductivity at different effective closure stresses and sand volume proportions.

Influence Factors of Multifunctional Viscous Drag Reducers and Their Optimization for Unconventional Oil and Gas Reservoirs.

Owing to the problems of guar gum fracturing fluid and conventional slickwater fracturing fluid systems in hydraulic fracturing of tight oil reservoirs, such as bad fracture network capacity, high damage, and low sand-carrying performance, researchers are actively looking for new alternative fracturing fluids. This study takes four commonly used additives for hydraulic fracturing of tight oil and gas reservoirs in western China, including the conventional polyacrylamide friction reducer EM30S, bioglue, thickener CHS-1, and high-viscosity friction reducer HVFR-1. By testing the water solubility, rheological properties, drag reduction, sand-carrying performance, imbibition oil displacement effect, and residue content of the four additives, the best additives suitable for hydraulic fracturing of tight oil and gas reservoirs were selected, and a set of indoor evaluations and the experimental method of screening hydraulic fracturing additives for tight oil and gas reservoirs were established. The research results show that the high-viscosity slickwater system composed of CND + HVFR-1 is more suitable for hydraulic fracturing of tight oil and gas reservoirs. Compared with the other three types of additives, CND + HVFR-1 fracturing fluid has good water solubility, and the dissolution time is less than 30 s. Therefore, in order to save construction time, the CND + HVFR-1 high-viscosity slickwater system is first recommended for field application. The research results of rheological properties show that although the apparent viscosity of high-concentration HVFR-1 + CND is low, the cross value of G' and G″ is the smallest (0.006 Hz) and the elastic modulus is the largest (4.554 Pa) corresponding to 1 Hz. HVFR-1 + CND has better sand-carrying performance when used as a sand-carrying liquid. CND + HVFR-1 not only achieves a friction reduction rate of more than 60% but also has the effect of imbibition oil displacement to improve oil recovery; it can easily break gels, and its low residue content can ensure rapid flowback after construction is completed, and the lower residue content also causes the least damage to the reservoir. At the same time, the establishment of this evaluation method provides a certain reference for other researchers who select fracturing fluids for tight oil and gas reservoirs.

Performance Evaluation of the Multifunctional Variable-Viscosity Slick Water for Fracturing in Unconventional Reservoirs.

The traditional guar gum fracturing fluid system has the drawbacks of the fracturing process of unconventional oil and gas deposits, such as high drag resistance and large residuum harm, which is gradually replaced by the system of the slick water fracturing fluid. The conventional slick water system, however, still has the features of low sand-carrying capability. Therefore, high-viscosity slick water is often used in fracturing operations, but most of the high-viscosity slick water is difficult to prepare, dissolve, and break gels, which needs to be improved. Based on the abovementioned problems, a new type of multifunctional variable-viscosity slick water is proposed in this paper. The self-made loop drag test unit, a dynamic crack sand-carrying model, a multifunctional core flow device, and other equipment were used for testing, and a set of systematic evaluation methods for the performance of multifunctional variable-viscosity slick water are established. In addition, the mechanism of improving sand-carrying capacity and increasing viscosity and solubilization was explained through the macroevaluation experiment of polymer properties and the analysis of the polymer microstructure. The experimental results show that compared with high-viscosity slick water, the multifunctional variable-viscosity slick water has good drag-reducing performance, the drag-reducing rate can reach more than 75%; the intersection value of viscoelastic modulus is about 0.01 Hz, the sand carrying capacity is higher; the gel-breaking time is faster, the residue content is lower, 38.5 ppm; it has the characteristics of low harm, the harm rate to the core is 18.30%; and it also has the performance of enhancing oil recovery.

A New Intermittent Pumping Design for Fluid Shortage Wells.

Low oil price requires oil companies to reduce costs and increase benefits. The wells with deficient fluid supplies approximately account for 20-30% of all producing wells, and this situation is even worse in the old oilfields. Intermittent production is an effective way to reduce the cost and increase the system efficiency to overcome the shortage of oil supply from the reservoir. The key is to optimize the intermittent pumping scheme, i.e., to design reasonable shut-in and operating periods. In this study, this is achieved using the dynamic change of the fluid level in the wellbore. From the electrical power curve to the dynamometer card, the dynamic drop of the fluid level can be obtained, and thus the optimal operation time of the well; at last, from the inflow performance of the well, the optimal shut-in period can be obtained. This method shows a good application in the field through a case study.

Study on the Mechanism of Nanoemulsion Removal of Water Locking Damage and Compatibility of Working Fluids in Tight Sandstone Reservoirs.

The invasion of external fluids, because of hydraulic fracturing for tight sandstone gas reservoirs, will cause the decrease of fracture conductivity and rock matrix permeability and decrease the flow of oil and gas. The nanoemulsion has a smaller molecular size and is used in combination with the fracturing fluid. After entering the formation, it can reduce the surface tension of gas/water, change the wettability of the rock surface, and improve the flowback rate of the fracturing fluid. In this study, a set of systematic evaluation methods was established in the laboratory to evaluate the mechanism and effect of removal of water locking additive in tight sandstone gas reservoirs. The adsorption experimental results of the nanoemulsion on the rock surface show that the adsorption of the nanoemulsion on the solid-phase particle surface is from strong to weak in the order of smectite, kaolinite, DB105X well rock powder, quartz sand, illite, chlorite, and ceramsite proppant. The experiment on the influence of the nanoemulsion on the spontaneous imbibition of reservoir rocks shows that when the gas permeability of reservoir rocks is K g < 5.0 mD, adding a nanofluid in the working fluid to change the wettability of reservoir rocks can effectively reduce the imbibition and retention of external fluids in reservoir rocks, thus reducing the "water locking damage". When the gas permeability of reservoir rocks is 5.0 mD < K g ≤ 1.0 D, the effect of changing the reservoir wettability to prevent the "water locking damage" is reduced. At the same time, the nanoemulsion has good compatibility with different types of fracturing fluid and is beneficial for improving the flowback rate.

Build-up of double carbohelicenes using nitroarenes: dual role of the nitro functionality as an activating and leaving group.

The construction of double carbohelicenes is highly fascinating yet challenging work. Disclosed herein is a streamlined and simplified synthetic route to double carbohelicenes starting from nitroarenes through sequential nitro-activated ortho-C-H arylation, denitrative alkenylation and intramolecular cyclodehydrogenation. In this synthetic strategy, the nitro group plays a dual role namely as a leaving group for the denitrative alkenylation and as an activating group for ortho-C-H arylation, which is distinct from those of aryl halides in a conventional coupling reaction. In this work, the palladium-catalyzed Heck-type alkenylation of nitroarenes has been presented, in which the conventionally inert Ar-NO2 bond is cleaved. This work provides a novel synthetic strategy for polycyclic aromatic hydrocarbons (PAHs).

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.

[A multi-center survey of hypertension and its treatment in patients with maintenance hemodialysis in Shanghai].

OBJECTIVE: To study the prevalence, treatment policy and control of hypertension in patients with maintenance hemodialysis, and to analyze the influencing factors of hypertension control. METHODS: We studied the current status of 1382 patients with maintenance hemodialysis in 11 dialysis centers in Shanghai, among them 809 were male, and 573 were female. Hypertension was defined as systolic blood pressure (SBP)≥140 and/or diastolic blood pressure (DBP)≥90 mm Hg (1 mm Hg=0.133 kPa). Those who had a history of hypertension and requiring antihypertensive therapy were also diagnosed as hypertension though their blood pressure was within normal range during the survey. Hypertension control was defined as blood pressure<140/90 mm Hg before each dialysis session. RESULTS: The prevalence of hypertension in the hemodialysis patients was 86.3%. The treatment rate and control rate in those patients were 96.8% and 25.5% respectively. More than half (50.4%) of patients were treated with only one kind of anti-hypertensive drug, and 34.4% with 2 kinds, 14.2% with 3 kinds, 1.0% with 4 kinds or more. Calcium channel blocker (CCB) was the most frequently prescribed drug (61.0%), followed by angiotensin II receptor blockers (56.4%), centrally acting anti-hypertensive agent (26.4%), beta blockers and alpha, beta-blockers (14.0%). The control rate of hypertension in those hemodialysis people was aggravated by the existence of coronary artery disease. The patients who need more kinds of antihypertensive agents have a poorer control rate of hypertension. The hypertension control rate elevated significantly with the adequate hemodialysis. CONCLUSIONS: There is a very high prevalence of hypertension in maintenance hemodialysis patients. Although the treatment rate is high, the control rate is unsatisfactory. So the control of hypertension in hemodialysis patient is still a clinical challenge. Appropriate dialysis adequacy, reasonable use of erythropoietin, treatment of heart disease and judicious use of antihypertensive drugs may be helpful to improve the clinical outcome.