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Composed of multi-strand parallel high-strength wires or steel strands, the stayed cables have been widely used recently in stayed bridges or suspension bridges owing to their light weight and high bearing capacity, especially the steel strands. Meanwhile, chloride-induced corrosion of steel strands is one of the most considerable factors for the durability of the stayed cable exposed to marine environments. The fatigue caused by both cyclic loading and corrosion can affect the life of the steel strands. Besides, the current studies related to the effects of the aforementioned two impact factors on the life of the steel strands either considered the fatigue only, or took the two impact factors into account separately. The coupling effects of fatigue and corrosion on the life of the steel strands are required to be further explored and discussed. Consequently, it is essential to create a model to predict the life of the steel strands with the coupling effects taken into consideration. In this paper, an indoor physical experiment of the steel strand specimens exposed to marine tidal environment was carried out. To avoid accidental errors, the whole specimens were divided into 20 groups, with each group having two steel wires with a 5 days, 10 days, and 15 days cycle for the test. The corrosion of steel strands was observed at various exposure times and it was found that the pits were formed on the surface with the chloride ion erosion to the steel strands. Deeper and sharper pits result in greater pitting-local stress and a shorter fatigue life, which is also the main reason for reducing the carrying capacity of the steel strands. However, a detailed description for this problem is lacking in current domestic and foreign literature, because the pit is hard to predict owing to its complex nature. In order to simulate the evolution of the pits, the stochastic pitting-corrosion model was set up by the neural network method to evaluate the pit evolutions over time. In addition, an empirical formula consisting of length&ndash, width ratios, length&ndash, depth ratios, and depth-to-width ratios of the pits was obtained to determine the stress concentration factor based on the multi-dimensional linear regression method. The fatigue notch factor of components can be deduced by the stress concentration factor, and the life of the steel strands can be deduced by both of them. The findings are expected to be useful in realistically predicting the durability of wire structures.

Abstract A study dealing with formation damage and damage control for horizontal wells drilled in the Shengli and Dagang (both in East China) sandstone formations is reported in this paper. The factors influencing the productivity of horizontal wells were quantitatively analyzed. The results show that formation damage is an important factor affecting productivity, compared with other factors, such as reservoir thickness, horizontal well length and anisotropy ratio of permeability, for the low permeable formations with permeabilities less than 80 md. It was also found that the effect of formation damage on production rate is constantly much higher for a horizontal well than that for a vertical well drilled in the same formation under the similar drilling conditions. To minimize the formation damage during horizontal drilling, three less-damaging drilling and completion fluids (a newly developed polymer mud, SN-1 oil emulsion mud and MMH mud) were used in these horizontal wells. The design criteria, formulation, properties and applications of these fluids were discussed. For each mud system CaCO3 was used as a bridging agent. The particle sizes of CaCO3 were selected based on the average pore sizes of the target formations. It was observed that the three mud system had provided excellent formation protection with much less skin factors and much larger percentages of regained permeability as compared with other commonly used drilling and completion fluids. The oil production rates of most horizontal wells are three to five times higher than that of their adjacent vertical wells, which is highly related to the effective prevention of formation damage. Introduction It is well known that the major purpose of horizontal well drilling is to increase the contact area with reservoir exposed in the well and thereby enhance well productivity. In recent years, the horizontal well technology has been developed quickly in China, and more than fifty horizontal wells with various radii, most of which were located in Shengli field, were drilled in the 90's. It should be noted that the difficulty and cost of drilling and producing increase with the augmentation of well productivity. One of the major concerns is that the drilling-induced formation damage may be more pronounced for a horizontal well than that for a vertical well in the same formation from the point of view of the production loss (i.e economic loss) although it is generally considered that the horizontal well will likely be more tolerant of formation damage than the vertical well since the horizontal completion interval length is much longer. Thus, in order to give a full play to the economic benefit of horizontal well technology, it is necessary to know the characters of damage accounted during horizontal drilling and to develop techniques to minimize the extent of damage caused by drilling muds. The formulations, performance and effectiveness of these drilling muds were discussed. All this work was in connection with the horizontal wells drilled in Shengli and Dagang low-permeable sandstone formations. The test procedures to evaluate drilling-induced damage are similar to those provided in Ref. 2. Both the values of skin factor and regained permeability are mainly used as the measures of damage in this work. Flow tests through field cores were conducted at ambient temperatures. All the core samples were taken from vertical wells in the same formation and saturated with synthetic formation brines. These tests involved comparing the final (regained) permeability, after treated with drilling fluids, to the initial undamaged permeability. P. 739

Abstract The oil-in-water emulsion drilling fluids, prepared by adding 5 12% mineral oil (or diesel) to water-based muds, have been widely used for stuck-pipe prevention in Shengli Oilfield. In some cases, the emulsion stability of this kind of mud systems is not strong enough to meet the requirements of drilling operations. To overcome this drawback, a solid emulsifier which is characterized by its very small particle size and the special wetting behavior (slightly water-wet), has been developed and successfully applied to improve the emulsion stability and other performance of these drilling fluids. Prior to the development of this technology, an extensive study dealing with the influence of various kinds of finely divided insoluble solid particles on the emulsification of oil and water was carried out. The substances used include bentonite, organophilic clay, kaolinite, barite, two kinds of calcium carbonate with different particle size, two kinds of silica with different wetting behavior, and the new solid emulsifying agent. Both emulsion stability experiments and drop coalescence experiments were performed to evaluate the contribution of these particles to emulsification. The measured final emulsion volume left after 12 hours and the half-life for water and oil drops were used as the measures of emulsion stability. The experimental data show that the type, size, concentration and wettability of the particles, and the presence of some surfactants control the type and stability of emulsions for a given oil/water system, and the fine particles of the solid emulsifier provide the most effective stabilization to water-continuous emulsions compared with other kinds of particles. Meanwhile, it can be observed that these particles also stabilize oil-continuous emulsions effectively in some cases since their wetting behavior is close to neutral. The newly developed oil-in-water emulsion mud stabilized by the solid emulsifier has become one of the major mud systems used in directional and horizontal well drilling in this oilfield. In addition to its improvement on emulsion stability, this solid emulsifier has proven to enhance wellbore lubrication and to be of benefit to the control of rheological parameters and filtration. The field applications of the emulsifier, and the typical formulation and properties of the mud system are reported in this paper. Introduction It has been well known that the fine solid particles existing in oil/water interfaces can stabilize emulsions. Many investigators presented the results on the effect of various finely divided solids, and the combinations of these solids and surfactants, on the stability of water/oil emulsions. Some of them discussed the mechanism by which particles stabilize emulsions. For example, Gelot et al. observed that water-wet particles such as Ca-bentonite tended to stabilize oil-in-water emulsions, while oil-wet particles such as carbon black tended to stabilize water-in-oil emulsions. Tadros and Vincent concluded that particles will tend to remain at the interface when the three-phase contact angle equals to 90 and play a role in preventing drop-drop coalescence in emulsions. Tambe and Sharma presented the experimental data to show the influence of various colloidal particles, such as calcium carbonate, barium sulfate, bentonite and carbon graphite on the stability of oil/water emulsions and claimed that these solids stabilized emulsions both by providing steric hindrance to the coalescence of oil and water droplets and by modifying the rheological properties of the interfacial region. They also thoroughly summarized the results of previous investigations. Most results described above were derived from fundamental work and did not involve with practical applications. Unlike the previous studies, the main objective of this study is to develop a solid emulsifier to improve the performance of drilling fluids. P. 561^

Objective To study the relationship between carotid arterial atherosclerosis,plaque and various cardiovascular risk factors with hypertension. Methods 490 patients with hypertension undergoing carotid artery ultrasound was used to measure carotid arterial intimae-media thickness and the plaque of carotid artery,then the relationship among cardiovascu lar risk factors,namely hypertension graduation,the course of hypertension gender,pulse pressure,age,gender,TC,TG,HDL-C, LDL-C,UA,CRP,FBG;Choose another 253 patients without hypertension as control group to do relevance index detecting and statistics analysis;Pick out 412 cases of patients with hypertension and neck atherosclerosis and adopt individuation voltage dropping resister treatment and use Aspiring 100mg qd,Sinvastation (20～40)mg qd. Then observe the variation between atherosclerosis degree and the cardiovascular events,all patients were followed -up for one year. Results Carotid atherosclerosis and plaque showed positive correlation with the level of hypertension,systolic pressure,Pulse pressure,and the course of hypertension.The factor is connected with cardiovascular danger such as TC、LDL-C、UA、CRP、FBG equally. The coronary artery disease showed positives correlation with hypertension and carotid arterial atherosclerosis. After consolidating the process of lowering artery pressure,adjusting blood lipid and doing comprehensive treatment,the symptom of atherosclerosis is improved significantly and the clinical coronary artery disease,the cardiovascular events,the death rate and the hospitalizing rate are dropped greatly. Conclusion Carotid arterial atherosclerosis and plaque are closely related to hypertension. Early comprehensive treatment can delay the development of atherosclerosis.