一种弱溶蚀酸液在砂岩储层酸化中的应用研究

为避免触发酸化储层改造中使用强溶蚀酸液体系造成的二次伤害和储层出砂,通过酸-岩溶蚀能力、抑制二次沉淀、天然岩心酸化模拟和单轴抗压分析研究了一种弱溶蚀酸液体系。该酸液体系溶蚀能力只有常规土酸酸液溶蚀能力的30%左右,对各种二次沉淀物质抑制能力均强于标准土酸。弱溶蚀酸液处理后岩心抗压强度下降率为土酸处理后的35.4%,综合酸化性能评价实验中弱溶蚀酸液体系能将被污染的岩心渗透率恢复到107.1%。弱溶蚀酸液体系实际应用海西部某油田某井W_(3)段Ⅵ、Ⅶ_(上)、Ⅶ_(下)油组砂岩储层,恢复该井产能且增油133.28 m^(3)/d,后期生产过程中未出现二次伤害和储层出砂,取得良好酸化增产效果。

酸性溶液对花岗岩残积土物理力学特性的影响

花岗岩残积土是华南地区进行工程建设时的常见地层之一,它的工程性质易受到周围环境的影响。采用人工方法制备了4种不同浓度的硫酸溶液浸泡后的试样,同时与原状试样进行对比,系统研究了不同浓度的硫酸溶液、不同的酸液溶蚀时间对花岗岩残积土试样物理、力学特性的影响。试验结果表明:(1)随着酸液浓度及酸液溶蚀时间的增大,试样的土粒比重减小、孔隙比增大、颗粒粒径级配变差;(2)试样的剪应力-剪切位移关系曲线类型会随着法向压力及酸液溶蚀作用而发生变化;(3)硫酸溶液浸泡后,试样的抗剪强度参数粘聚力和内摩擦角都降低了,但粘聚力的降低效果更明显。

Corrosion behavior of Hastelloy C22 coating produced by laser cladding in static and cavitation acid solution

The Hastelloy C22 coatings on Q235 steel substrate were produced by high power diode laser cladding technique. Their corrosion behaviors in static and cavitation hydrochloric, sulfuric and nitric acid solutions were investigated. The electrochemical results show that corrosion resistance of coatings in static acid solutions is higher than that in cavitation ones. In each case, coating corrosion resistance in descending order is in nitric, sulfuric and hydrochloric acid solutions. Obvious erosion-corrosion morphology and serious intercrystalline corrosion of coating are noticed in cavitation hydrochloric acid solution. This is mainly ascribed to the aggressive ions in hydrochloric acid solution and mechanical effect from cavitation bubbles collapse. While coating after corrosion test in cavitation nitric acid solution shows nearly unchanged surface morphology. The results indicate that the associated action of cavitation and property of acid solution determines the corrosion development of coating. Hastelloy C22 coating exhibits better corrosion resistance in oxidizing acid solution for the stable formation of dense oxide film on the surface.

Corrosion properties of stainless steel 316L/Ni-Cu-P coatings in warm acidic solution

In order to improve corrosion resistance of stainless steel 316L in warm acidic solution, Ni？Cu？P coatings with high copper and phosphorus contents were deposited onto stainless steel 316L substrates via electroless plating. The structure of the film and its resistance to corrosion in a warm acidic environment were investigated using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction spectrometry （XRD）, polarization curves, electrochemical impedance spectroscopy （EIS）, and dipping corrosion tests, respectively. The results demonstrate that Ni？Cu？P coatings consist of two types of nodules, which are 19.98% Cu and 39.17% Cu （mass fraction） respectively. The corrosion resistance of the 316L substrate when subjected to a warm acidic solution is significantly improved by the addition of the new type of the Ni？Cu？P coating. The as-plated coatings demonstrate better corrosion resistance than annealed coatings. As-plated coatings and those annealed at 673 K are found to corrode selectively, while pitting is observed to be the main corrosion mechanism of coatings annealed at 773 and 873 K.

Corrosion Behavior of a Titanium Alloy in Hot Nitric Acid Condensate

The corrosion behavior of a titanium-5% tantalum alloy （Ti-STa） in hot nitric acid condensate was investigated to understand aging behavior ofreprocessing equipments. On the basis of long-term immersion tests, it was determined that the corrosion of Ti-STa in nitric acid condensate is accelerated with an increase in the concentration. The corrosion rate was nearly constant during the immersion test and the coupons suffered from uniform corrosion. In addition, it is important to note that the nitric acid concentration in the condensate increased on addition of metal salts to the heated nitric acid solution. The larger valence of metal ions was contributed to the increase in the concentration of nitric acid condensate. Consequently, the metal salt in the heated nitric acid solution accelerates the corrosion of Ti-STa in the condensate. Therefore, the nitric acid condensate condition should be carefully considered for the corrosion environment of titanium and its alloys.

Inhibition effect of 2-amino-5-ethyl-1,3,4-thiadiazole on corrosion behaviour of austenitic stainless steel type 304 in dilute HCl solution

The corrosion inhibition of type 304 austenitic stainless steel by 2-amino-5-ethyl-1, 3, 4-thiadiazole(TTD) compound and the electrochemical behaviour in dilute HCl solution were investigated through potentiodynamic polarization test, mass loss techniques and potential measurements. The results show that the organic derivative is highly effective with a maximum inhibition efficiency of 70.22% from mass loss analysis, while 74.2% is obtained from polarization tests. Observation of the scanning electron micrographs shows the absence of corrosion products due to electrochemical influence of TTD on the surface morphology of the steel. X-ray diffractometry reveals the absence of phase compounds and complexes on the steel samples after exposure. TTD adsorption on the steel surface obeys the Langmuir, Frumkin and Freundlich adsorption isotherms. Corrosion thermodynamic calculations reveal the inhibition mechanism occurs through chemisorption process and results from statistical analysis depict the strong influence of inhibitor concentration on the electrochemical performance of the TTD.

Effects of KMnO_4 on microstructure and corrosion resistance of microarc oxidation coatings on 2024 aluminum alloy

Microarc oxidation （MAO） coatings were prepared on 2024 aluminum alloy in a Na2SiO3-KOH electrolyte with KNinO4 addition varying from 0 to 4 g/L. The microstructure and phases of the coatings were characterized by scanning electron microscopy （SEM） and X-ray diffractometry （XRD）, respectively. The corrosion resistance of MAO coatings was evaluated by electrochemical potentiodynamic polarization in 5% （mass fraction） NaCl solution. The results show that when KMnO4 is added into base electrolyte, the growth speed of oxide coatings is increased obviously. The main phase of oxide coatings is Al2O3, and the contents of MnO2 and MnEA104 phases are increased at the top of oxide coatings with increasing the concentration of KMnO4. The solute elements participate in forming the oxide coatings. When a proper concentration of KMnO4 （2.5 g/L） is added into the base solution, the micropores of the MAO coatings are small and compact, and the corrosion resistance of oxide coatings is increased largely.

New Synthesized （3-（3,4-dimethoxyphenyl）isoxazole-5- yl） Methanol as Corrosion Inhibitor on Steel in 1 M HCI

The inhibition of corrosion of steel in molar hydrochloric acid solution by new synthesized DMI （（3-（3,4-dimethoxyphenyl）isoxazole-5-yl） methanol） compound is studied by weight loss and electrochemical polarization measurements. The two methods give consistent results. The polarization curves indicate that the DMI compound acts as mixed-type inhibitor. This compound is efficient inhibitor. The inhibition efficiency increases with the increase of inhibitor concentration to reach 96% at 10-3 M for DMI. The temperature effect on the corrosion behavior of steel in 1 M HCI with and without the DMI compound at 10-3 M is studied in the temperature range from 298 to 318 K. The adsorption of inhibitor on the steel surface is found to obey the Frumkin adsorption isotherm model. From the adsorption isotherm, some thermodynamic data for the adsorption process （f, K and △Gads） are calculated and discussed.

Microstructure characterization and electrochemical corrosion behavior of Zn and Zn/Mg alloys in H_2SO_4 solution

The three systems of pure Zn, Zn-0.10% Mg(mass fraction), and Zn-0.15% Mg(mass fraction) were cast under controlled atmosphere and their microstructures were characterized by SEM/EDS analysis. The electrochemical corrosion behavior of these three samples was examined in the very aggressive solution of 50% H2SO4(mass fraction) using electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization measurements. The results show that magnesium improves in some extent the corrosion resistance of pure Zn in 50% H2SO4(mass fraction) confirmed by EIS test. Results of polarization measurment also demonstrate that small amount of Mg significantly improves the passivation of Zn in the test solution. Results of surface morphology of the samples and EDS analysis reveal that Mg reduced the corrosion attacks to pure Zn.

The compressive strength experimental study of cemented soil under H2SO4 corrosive in earlier period

In order to simulate and study the erosion effect process such as the changes of corrosive depth and unconfined compression strength of cemented soil sample in earlier period from 0 day to 60 days, a series of tests including unconfined compressive tests, measuring the blocks＇ sizes, and taking photos, are conducted on the cemented soil blocks which were cured in different concentrations of H2SO4 solutions. The results of tests show that the corrosive depth is increasing and the unconfined compression strength is decreasing with the increase of H2SO4 solution concentration at the same erosion time, and the corrosive degree is increasing with the corrosive time. In the earlier state, the corrosive effect is serious, but the effect becomes slow in the later state in the same concentrated H2SO4 solution. After take statistics the date, a coefficient a is put forward to predict the reduction of the compressive strength of cemented soil in various concentration of H2SO4 solution, which could be used in practical design.