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This study investigates corrosion of carbon steel balls and the valve seat during acid cleaning in inhibited HCL(1) solution. The ball and seat were electro less nickel plated followed by tungsten carbide and Inconel 625 via HVOF(2) technique respectively. Weight-loss testing showed that corrosion rate was 137.4 MPY(3) over an exposure period of 6 hours in 10 Vol % (Volumetric) inhibited HCl solutions at 35 °C for Inconel 625 coupons. The 32 inch valves were exposed to inhibited HCl solution with different concentrations (3 Vol%, 8 Vol%, 12 Vol% and 15 Vol% with maximum pH=2) accordingly. Exposure time varies from one to ninety hours. Due to poor sealing of some ball valves after chemical cleaning, corrosion resistance of eighteen coupons were evaluated by EIS(4). The coupons were coated under similar conditions to that of balls. In this case study, corrosion mechanism affecting the extent of damage on each coating along with surface properties and material is discussed.
One of the most prominent concerns in the oil and gas production industry is the behavior of materials in an aggressive environment which contributes to corrosion of the surface. This effect plays a major role in equipment reliability and maintenance costs, especially when the equipment is in operation at off-shore industries where internal components are exposed to corrosive environments. The erosion and corrosion resistance of metallic alloys available in a wide range of such equipment can be improved in an effective and economical way by means of HVOF coatings. This thermal spray process has been developed to produce extremely high spray particle velocities 1The reason HVOF process is widely used is because it produces low porosity surface (<1%), low oxide content (< 1%), and highly adherent coatings.23Some defects such as porosities, micro cracks and oxide phases that could be in the coatings serve as sources for corrosion attack. These defects can be minimized or partially eliminated by a careful study of coating microstructures and control of processing parameters and thus improving the corrosion resistance.4The binder material provides toughness and adhesion for a coating. A binder with poor corrosion resistance in a service environment can cause delamination between coating and substrate.5 Zhao investigated the corrosion mechanism of HVOF sprayed NiCrBSi coatings in 3.5 Vol% NaCl(5) with pH(6) adjusted to 3 by addition of acetic acid and founded that the main failure mechanism of the coating is exfoliation or laminar peeling off.6 So, it is required to have a good understanding of the coating corrosion properties on the component before subjecting it to a potentially corrosive service environment. Then, the risk of malfunction of the component from corrosion attack is greatly reduced. Another way to improve corrosion resistance is application of Ni-based alloys in engineering applications such as pressure vessels, pipe, and valve because of their corrosion-resistant properties. They have been widely used in high-temperature and high-pressure H2S environments.7Nickel-based alloy coatings are often used by thermal spraying with novel mechanical properties such as improved hardness, toughness, corrosion and wear resistance to meet many functional requirements in advanced engineering applications.8,9,10,11 The corrosion and wear resistance can be provided by chromium as a consequence of its passivation ability in super alloys. The present study was conducted in order to investigate the corrosion properties of steel substrate coated with the Inconel 625 alloy(7), and tungsten carbide applied by HVOF thermal spray on ENP(8) coated 32 inch carbon steel ball valve and also eighteen coupons in plate format in HCl solution. The 32 inch valves were exposed to inhibited HCl solution with different concentrations (3 Vol%, 8 Vol%, 12 Vol% and 14.5 Vol% with maximum pH=2) during chemical cleaning to remove internal scale. Exposure time varies from 1 to 90 hours. Exposure time and acid power varies in each operation. This real case study was established because of poor performance of some ball valves after acid cleaning. So this was conducted with the aim of determining the corrosion performance of the mentioned coating in HCl aqueous solution. Regarding that, polarization and EIS test were performed according to ASTM(9) G312 and ASTM G513 on the eighteen coated substrates samples immersed in 5%, 10% and 15% HCl solution as an electrolyte.
Unwanted water production is becoming a matter of much concern in oil industry. The existence of an aquifer in a reservoir with thin producing layers and also in the situations that producing mechanism is relied on water, this issue becomes more noticeable due to water coning phenomenon. During this phenomenon, the water phase moves towards producing well in a conical shape. As water cone reaches the well, water cut increases instantly. High water cuts have negative effect on total recovery factor and cause extra pressure drops. This would also result in corrosion problems, environment issues, water disposal costs and in the end speed up well abandoning operation. So far, several methods and techniques have been proposed to combat water coning. In this paper, we compare efficiency of gel injection, oil barrier and DWS methods using simulation. We also consider the variables in each method that may alter the efficiency of the method and determine the most effective and applicable combination for each method individually with the help of Eclipse simulator.
The results show that more diffused gels and less injection intervals would improve the gel injection and oil barrier methods efficiencies, respectively. However, these methods have shown to have injection pressure limitations. DWS efficiency improves with increased water production rate but it is limited to bottom hole pressure and reverse coning. DWS and gel injection are the most effective methods against water coning in conventional and tight reservoir, respectively.
Abstract Geological sequestration of carbon dioxide through enhanced oil recovery operation has been recognized as one of the more viable means of reducing emissions of anthropogenic CO2 into the atmosphere. The objective of this paper is to find the best EOR scenario for a compositional grading Iranian oil reservoir to be fed by a giant power plant which produces huge amount of CO2 emission, through simulation study. For this purpose a three-dimensional simplified yet realistic model of the reservoir considering compositional grading was built based on long term production data. Various simulation cases to combine different injection schemes and examining the effect of injection rate were conducted to propose an injection-production strategy that can optimize the oil recovery along with CO2 storage. This study is the first attempt to investigate technical and economic aspects of simultaneous CO2-EOR and sequestration for the nominated reservoir. Besides, this approach could be used for any gas cycling and natural gas storage process into this reservoir. The results presented in the study clearly demonstrated that continuous CO2 injection scheme through one injection and one production well, is the best scenario for simultaneous EOR and sequestration/gas storage which lead to higher CO2 storage and oil recovery efficiency. Through continuous CO2 injection, this reservoir has potential for large scale CO2-EOR and storage projects (injection of more than 240 thousand metric tons of CO2 per year with only one injection well without any field development plan). Finally an economic study is performed to confirm the best scenario.
You, Z.. (University of Adelaide) | Kalantariasl, A.. (Shiraz University) | Schulze, K.. (DEA Deutsche Erdoel AG) | Storz, J.. (DEA Deutsche Erdoel AG) | Burmester, C.. (DEA Deutsche Erdoel AG) | Künckeler, S.. (DEA Deutsche Erdoel AG) | Bedrikovetsky, P.. (University of Adelaide)
Abstract Compressibility needs to be accounted for when estimating injectivity decline for water disposal in gas reservoirs and in closed aquifers, and for waterflooding of gas-condensate fields. The problem with given wellbore pressure at the injector aims avoiding the reservoir fracturing. An analytical model is developed that provides well injectivity index decline with time. Under this model, the solution of damage-free compressible flow in a closed reservoir is asymptotically matched with the impedance growth formulae for incompressible flow in the well vicinity. For the well regime of a given wellbore pressure, the injection rate decline is described by a nonlinear integro-differential equation that is solved iteratively. The solution under the field conditions investigated shows that well impedance grows faster during deep bed filtration than during external cake formation. This unusual pattern is explained by low permeability of the reservoir. Well impedance is more sensitive to the effect of formation damage than to the compressibility effect of rock and water. Lower formation damage, higher compressibility, or lower injected particle concentration results in larger total injection volume into a closed reservoir.
Abstract The objective of this paper is to present a co-precipitation technique with calcium carbonate for removal of heavy metals ions from oil field brine. Metals such as Mercury, Copper and Lead can be removed by the co-precipitation technique. In this work, parameters such as pH, injection time and concentration of reactants were optimized in other to obtain maximum removal efficiency. The results showed that pH has a significant effect while the injection time and reactant concentrations were less effective to remove the metals. Based on the SEM, ICP and hydrometer analysis, the optimum experimental conditions were the pH of 10, the injection time of 20 min and the reactant concentration of 0.5 mol percent. Approximately, more than 90 percent of mercury, lead and copper was removed employing co-precipitation techniques with calcium carbonate. Scanning Electron Microscopy analysis indicates that 200 rpm is the optimum rotational speed which leads to the formation of small particles. Finally, this study showed especially that the co-precipitation technique is a good alternative to remove the heavy metals especially mercury from the contaminated oil field brine.
The pdf file of this paper is in Russian.
The objective of this paper is to present a co-precipitation technique with calcium carbonate for removal of heavy metals ions from oil field brine. Metals such as Mercury, Copper and Lead can be removed by the co-precipitation technique. In this work, parameters such as pH, injection time and concentration of reactants were optimized in other to obtain maximum removal efficiency. The results showed that pH has a significant effect while the injection time and reactant concentrations were less effective to remove the metals. Based on the SEM, ICP and hydrometer analysis, the optimum experimental conditions were the pH of 10, the injection time of 20 min and the reactant concentration of 0.5 mol percent. Approximately, more than 90 percent of mercury, lead and copper was removed employing co-precipitation techniques with calcium carbonate. Scanning Electron Microscopy analysis indicates that 200 rpm is the optimum rotational speed which leads to the formation of small particles. Finally, this study showed especially that the co-precipitation technique is a good alternative to remove the heavy metals especially mercury from the contaminated oil field brine.
In the present paper physical model tests are carried out in order to further understanding of hydrodynamic processes that surround a Middle-Rubble Mound structure when it has been subject to irregular waves. Particularly, the transmission coefficient, as well as the spectrum transformation has been analyzed. This analysis suggests that with an increase of wave height around a Middle-Rubble Mound, the transmission coefficient extremely increases at each water level (SS, HHW, MSL and LLW). Moreover, when the water level changes from SS to LLW, transmission coefficient suddenly reduces.
Heidari, Mohammad A (Islamic Azad University Science and Research branch) | Habibi, Ali (University of Tehran) | Ayatollahi, Shahab (Shiraz University) | Masihi, Mohsen (Sharif University of Technology) | Ashoorian, Sefatallah (Sharif University of Technology)
Dilute Surfactant flooding is one of the significant processes in chemical flooding. Many oil reservoirs became appropriate candidates for surfactant/water flooding when screening criteria developed. Injected surfactant tries to mobilize the residual oil that was trapped in interstice. The main contributing mechanism for oil recovery improvement by surfactant flooding is rock wettability alteration. Wettability is a one of the proper index in choosing the best approach for a successful surfactant flooding which tiny change in wettability alteration will lead to improve oil recovery. This experimental study investigated the effect of different aging time and temperature on wettability alteration with exact soaking time to find the optimum condition. Afterwards, coreflooding experiments were performed to determine the impact of dilute cationic surfactant slug with huff ‘n’ puff(cyclic 7 days) method on displacement sweep efficiency in the carbonate core from one of the Iranian oil field. Besides, contact angle and interfacial tension (IFT) measurements were done to provide the supplementary data for a surfactant/waterflooding. The optimum concentrations of C19tab, were determined by measuring interfacial tension values of the crude oil in contact with surfactant solutions, which were prepared from synthetic saline water. The results obtained from laboratory showed a reduction in residual oil saturation by changing contact angle and IFT reduction between oil and water. Aging is known as important parameter for researcher to alter the wettability. Furthermore it proves effect of wettability alteration is more than IFT reduction.
Al-Sulaimani, H.. (Sultan Qaboos University) | Al-Wahaibi, Y.. (Sultan Qaboos University) | Al-Bahry, S.. (Sultan Qaboos University) | Elshafie, A.. (Sultan Qaboos University) | Al-Bemani, A.. (Sultan Qaboos University) | Joshi, S.. (Sultan Qaboos University) | Ayatollahi, S.. (Shiraz University)
Summary In this study, a biosurfactant produced by a Bacillus subtilis strain isolated from oil-contaminated soil from an Omani oil field was tested for its potential in enhancing oil recovery by a series of coreflooding experiments. It was found that the performance of the biosurfactant was increased by mixing with chemical surfactants, by which the maximum production went up to 50% of residual oil at a mixing ratio of (50:50). The second objective of this study was to investigate the effects of the biosurfactant on wettability alteration and to estimate its tendency to loss caused by adsorption. The influence of biosurfactant on wettability was studied by contact-angle measurements, atomic force microscopy (AFM) technique on few-layer graphene (FLG) surfaces, and Amott wettability tests on Berea sandstone cores. Contact-angle measurements showed that the wettability of the biosurfactant solution changes to more oil-wet as the angle decreased from 70.6 to 25.32° when treated with 0.25% (w/v) biosurfactant solution. Amott testing showed a change in wettability index from strongly water-wet in the untreated core toward less water-wet in biosurfactant-treated cores. These results confirmed the ability of the biosurfactant to alter the wetting conditions against different surfaces, thereby serving as a mechanism for enhancing oil recovery. The maximum loss of biosurfactant caused by adsorption was 1.2 mg/g of rock, which is comparable with reported chemical-surfactant values.
ABSTRACT The corrosion inhibition of carbon steel was studied by using an amido-imidazoline derivative and halide ions as an additive in CO2-saturated 3% NaCl solution with electrochemical techniques. The corrosion rate of the steel decreased with increase in the studied inhibitor concentration, while the inhibition efficiency increased and synergistically enhanced on addition of iodide ions. The values of synergism parameter found to be greater than unity. The experimental results revealed that the presence of iodide ions in the solution stabilized the adsorption of imidazoline molecules on the steel surface thereby improving the inhibition efficiency of the inhibitor. Furthermore, the adsorption of amido-imidazoline on the steel surface followed the Langmuir adsorption isotherm and it was chemically adsorbed on the surface of steel. The synergistic effect of iodide ions and amido-imidazoline was due to co-adsorption of iodide ions and amido-imidazoline molecules which was synergistic in nature. INTRODUCTION Carbon steels are widely used in oil and gas industry for numerous purposes. Although their corrosion resistance is limited, these materials are preferred to others due to economical reasons. API 5L(1) is a general carbon steel which is used for fabrication of flow and transition pipelines in oil and gas industry. One of the most frequent and aggressive environments found in the petroleum industry is a fluid with high concentrations of chlorides containing carbon dioxide which leads to CO2 corrosion, usually called sweet corrosion. 1-3 There are many variables associated with CO2 corrosion process including pH, temperature, pressure, flow regime, steel composition, inhibitor, brine chemical composition, the nature of surface films and etc. 4 The use of carbon steel in conjunction with corrosion inhibitors is the most economic option for many oil/gas projects, including in-field flow lines and long, large diameter export lines. Typical corrosion inhibitors used in oil/gas field applications are organic compounds and are employed in small concentrations.