PETROLEUM RESEARCH
Year:2010 | Volume:20 | Issue:63|Papers Count:8

Internal corrosion in pipelines is a significant problem in oil and gas transmission systems. Corrosion severely affects pipeline operations, leading to loss of production, unscheduled downtime for maintenance or repair, and even catastrophic failure, which impacts health, environment, and safety. This paper presents pulsed eddy current method as an advanced, non-destructive technique in corrosion detection on unburied gas pipelines. Moreover, this method provides promising results in internal corrosion detection of gas pipelines without removing insulation from the pipe. In this paper, first, the principals of pulse eddy current method are pointed out. Then, the pulsed eddy current test on a pipe is simulated by Maxwell software to obtain test parameters. Finally, corrosion on an isolated gas pipe is measured using pulsed eddy current test and the results obtained are verified.

Shales are found in over 75% of drilled profiles and create 90% of wellbore stability problems. During drilling in shale formation using numerical and analytical methods and considering correct and logical parameters, one can decrease the costs of wellbore walls instability. This study has been performed on the effect of physical and geomechanical properties of shale on wellbore stability in one of Iranian oil fields. In this study, a stability analysis of unstable shales has been done in a well section by numerical (FESTO3 software) and analytical methods. The mud weight window for different states of in situ stresses was suggested using analytical method. One of these states was studied and the optimum mud weights were proposed by numerical method and the results were compared. The research shows that understanding the state and magnitude of principal stresses can drastically affect the analyses.

High formation pressure is the most critical problem hindering formation of gas hydrates in industrial scale for storage and transportation of natural gas. The effects of tetrahydrofuran (THF) and tetrahydropyran (THP) on the phase equilibrium of methane hydrate have been studied. The addition of THF at different concentrations of 1, 2.5 and 6 mol % and THP at 6 mol % aqueous solutions caused hydrate equilibrium pressure to drastically reduce at a specified temperature. While the equilibrium pressure of methane hydrate is about 34 MPa at 293K, this equilibrium pressure decreased to about 2.5 MPa using 2.5 mol % of THF. Furthermore, the hydrate equilibrium temperature greatly increased at a specified pressure. The equilibrium temperature of methane hydrate at 5 MPa is about 278K. This equilibrium temperature increased to about 306K using 6 mol % of THF.

In this study, using the results of performed shale formation Characterizatins and the history of drilling in Iranian oil fields, an environmentally friendly water based drilling fluid is designed to replace the oil based drilling fluids. This drilling fluid has desirable properties in drilling water sensitive formations. New drilling fluid additives including shale inhibitors, new polymers and sized solid particles have been used to prepare this new drilling fluid. The most important properties of this new drilling fluid are controlling the mud filtrate and pressure invasion to the formation, clay mineral alteration and activity reduction, improvement of the integrity of drilling cuttings, reduction in formation damage, stability at high temperatures, stability in acidity changes and the compatibility by drilling fluids dilution during drilling operation. The lubricity and shale cuttings recovery of this new drilling fluid are better than those of other similar water based drilling fluids. Replacing this drilling fluid by oil based drilling fluids in drilling industry will be a great means to protect the environment and drilling personnel in addition to being economically advantageous.

Forces of drilling bit cause a lot of changes in rock characteristics, especially in rock mechanical properties. Changes of reservoir lithology cause pressure drop around wellbore during production procedure. Routine tests were carried out in all the wells after completion and unexpectedly high Darcy skins were estimated from the test data for all of the wells. In order to prepare prevention and remediation plans, it is crucial to understand the source of the skin. Determination of skin factor due to changes in drilling process (force and tension of drilling bit) around wellbore is very critical. The main purpose of determination of drilling bit effects is to control and prevent formation damage around wellbore. A lot of research has been performed regarding skin factor around wellbore. However, given the effects of drilling process such as stress on skin factor, attempt has been done to determine the effects of these parameters on skin factor around wellbore. The results of these analyses prove effective and controllable influence of drilling and skin factor around wellbore. The research shows controlling and reducing of skin factor around wellbore by appropriate planning of drilling and drilling bit. Another aim of this research is the explanation of the relation among different processes in petroleum industry to prevent formation damage. By careful examination of the structure before drilling planning and drilling bit selection, formation damage will reduce dramatically and destructive pressure drop in reservoir can also be prevented.

Experimental solubility data for H2S in aqueous solutions of N-methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA) and monothanolamine (MEA) have been measured at various temperatures (40, 55 and 70 oC) and partial pressures of H2S ranging from 20 to 2000 kPa. Solubility data were obtained in a 250 mL autoclave and analyzed by chemical methods. The autoclave was equipped with a pressure transmitter with an accuracy of +/- 0.01 psi and temperature indicator and controller with an accuracy of +/- 1°C. The compositions of liquid phase were analyzed by gas chromatography using a flame ionization detector (FID). All experiments were carried out in triplicate. Solubility data were correlated by M-KE (modified Kent-Eisenberg) model and equilibrium constant of alaknolamine protonation reaction was expressed by correlation in terms of temperature, H2S partial pressure (or loading) and alkanolamine concentration. In all cases, it was found that the models were able to give a relatively good H2S loading over a wide range of operating conditions. Therefore, the M-KE model may easily predict the solubility of acid gases in alkanolamine aqueous solutions. Average Absolute Deviation (AAD) for modeling of these alkanolamines by M-KE method are 1.75, 1.92, 2.48 and 1.27 for DIPA, DEA, MDEA and MEA aqueous solutions, respectively.

Oily wastewaters and oil-in-water emulsions are two major environmental pollutants. However, industrial oily wastewaters, though they may be lower in volume, contain much higher concentrations of pollutants. Treatment of the oily and greasy wastewater of Tehran refinery was experimentally studied using an ultrafiltration (UF) system. In the experiments, a UF membrane Polysulfone (PS) 30 kDa and sample from Tehran refinery outlet wastewater of the API unit were used as feed. Effects of different operating parameters such as transmembrane pressure (TMP), cross flow velocity (CFV), and temperature on permeation flux, fouling resistance and UF rejection were studied. According to the results, permeation flux was found to improve with increasing TMP, CFV and temperature at constant feed concentration. Fouling of the membrane completely follows Hermia’s model (filtration cake mechanism). Analysis of the UF process showed 99.2, 75.4, 63.3, 42.3, 23.1, 100 and 97.9 % decreases in oil and grease content, total organic carbon (TOC), chemical oxygen demand (COD), biological oxygen demand (BOD5), total dissolved solids (TDS), total suspended solids (TSS) and turbidity, respectively. A comparison of the results shows that UF performs better than conventional biological methods. The results showed that refinery wastewater treatment by using UF process is possible. The obtained UF permeates are suitable to discharge into the environment, even in the special regions in accordance with international requirements.

Oil pollution in marine environments is a global problem. Annually, large amounts of oil are released to marine environments. Persian Gulf is a strategic place where approximately 60 % of oil transfer takes place. In order to isolate crude oil degrading bacteria, coastal sand and sea water samples were collected from different zones in Persian Gulf. Crude oil degrading bacteria were then screened in selective media and strains, which showed high growth rate and crude oil removal, and selected for further study. These strains were identified by biochemical and molecular methods. The results showed that these strains belonged to Acinetobacter and Pesudomonas genus. Experiments were designed using Taguchi method by selecting six factors including temperature, nitrogen source, oil concentration, carbon source and degradative bacterium. Five factors had three levels and one (temperature) had two levels and thus L18 experiments were carried out. The results obtained from Taguchi experiments showed that temperature has no effect on biodegradation, although biodegradation can occur between 30-37°C. (NH4)2SO4 had the best effect on biodegradation among nitrogen sources. The rate of biodegradation in the presence of a chemical surfactant is greater than that in the absence of one and of the two surfactants used in this study tween 80 was more effective. Biodegradation dramatically decreased when the concentration of crude oil increased from 1 to 4%. When an additional carbon source was used, the rate of biodegradation increased. Mixed culture and A. calcoaceticus strain BS had the same effect on biodegradation but both levels were greater than P. aeruginosa AS. All factors have 95.3% contributions and the remaining 4.7% percent was the experimental error. Efficiency of Taguchi design was 77%. By using the strains obtained in this investigation and future assessment of the efficiency of these strains on saline water, oil contamination in Persian Gulf can be reduced.