Iranian Journal of Oil & Gas Science and Technology
Volume:9 Issue: 3, Summer 2020

The organic geochemical characterization of crude oil samples from the oil fields of the Niger delta was carried out using gas chromatography–-mass spectrometry (GC–-MS) to genetically characterize the oil samples in terms of their biomarker composition. Geochemical characteristics such as depositional environments, kerogen type, and source of organic matter were analyzed using aliphatic biomarkers as a supporting tool. Five samples were randomly collected from Tebidaba, Clough Creek and Azuzuama fields in Bayelsa State, Nigeria. The saturated hydrocarbons were analyzed using GC–MS. The n-alkanes, isoprenoids, biomarkers hopanes, and steranes fingerprints were extracted from chromatogram for m/z 57, 191, 217 values respectively. The results revealed that the five studied samples were characterized by C29 sterane predominance and the presence of oleanane, depicting organic matter with vascular land plant material inputs and a deltaic contribution. Ternary plots showed that the oils were deposited in an estuarine environment. The pristane (Pr) /nC17 versus phytane (Ph)/nC18 showed that TEB 08 and WELL 2 are in the anoxic environment inferring kerogen II and a mixture of types I and II respectively. TEB 12, CCST, and AZU ST has kerogen type III deposited in an oxic environment.

The imbibition process is known as one of the main production mechanisms in fractured reservoirs where oil/gas-filled matrix blocks are surrounded by water-filled fractures. Different forces such as gravity and capillary play a role in production from a fractured reservoir during imbibition and complicate the imbibition process. In previous works, single-parameter models such as the Aronofsky model and Lambert W function were presented to model imbibition recovery from matrix blocks. The Aronofsky model underestimates early time recovery and overestimates late time recovery, and Lambert W function is suitable for water wet cases. In this work, a data bank of different experimental and numerical imbibition recovery curves at various rock and fluid properties were collected. Then, a rigorous analysis was performed on the models utilized to describe oil/gas recovery during the imbibition process. In addition to investigating the single-parameter models, two-parameter models used for dose-response modeling, including Weibull, beta-Poisson, and Logit models were examined. The results of this work demonstrate that using two-parameter models can improve the prediction of imbibition behavior. Moreover, among the two-parameter models, the Weibull has the capability to describe the imbibition process better. The Aronofsky model underestimates early time recovery and overestimates late time recovery, and Lambert W function is suitable for water wet cases. In this work, a data bank of different experimental and numerical imbibition recovery curves at various rock and fluid properties were collected. Then, a rigorous analysis was performed on the models utilized to describe oil/gas recovery during the imbibition process. In addition to investigating the single-parameter models, two-parameter models used for dose-response modeling, including Weibull, beta-Poisson, and Logit models were examined. The results of this work demonstrate that using two-parameter models can improve the prediction of imbibition behavior. Moreover, among the two-parameter models, the Weibull has the capability to describe the imbibition process better.

A device is designed and constructed for measuring the equilibrium surface tension of water and a number of other solutions. The measured equilibrium surface tension of water, as a reference fluid, has good consistency with literature data. Moreover, the equilibrium surface tension of the aqueous solutions of surfactants and polymer composed of sodium dodecyl sulphate (SDS), Triton CG-110, dimethyl di-dodecyl-ammonium bromide (DDAB), and polyethylene glycol (PEG) with different molecular weights of 200, 300, 400, and 600, as well as that of the ternary solutions of SDS/PEG/water, Triton CG-110/PEG/water, and DDAB/PEG/water at 293.15 K and atmospheric pressure are measured. The equilibrium surface tension of the aqueous solutions of PEG 600 are measured at 296.15 K because PEG 600 is solid at 293.15 K. The measured data are compared with the predictions of thermodynamic models, and the results show that Redlich-Kister (RK) model has the lowest error in predicting the experimental data.

Abstract Although the hydrogen induced cracking (HIC) is recognized as one of the destructive modes for pipeline and component steels serving in sour environments, the behavior of the HIC is still not fully understood. On the other hand, although many efforts have been made to identify the effects of hydrogen on laboratory steel specimens, the study of actual industrial samples has received less attention. In this paper, we have studied the mechanism of the HIC in a damaged pipe of a real case study of the oil and gas industry (finger type slug catcher) using detection, characterization, and microstructural investigation methods. The detection of the HIC in the specimens by advanced ultrasonic techniques, failure analysis using tensile tests, chemical composition analysis, optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), and energy-dispersive spectroscopy (EDS) techniques and their correlation with the microstructure, type, and morphology of the inclusions were conducted. The results indicated that the value of elements, especially carbon (0.13 wt %) and manganese (1.44 wt %), satisfies the requirement of API 5L specification. Furthermore, the inclusions, such as elongated manganese sulfide and spherical aluminum oxide, and the pearlite grains or the interfaces of the ferrite–pearlite phases played an essential role in the HIC phenomenon as nucleation and propagation places of cracks. It was also observed that HIC cracks were mostly initiated and propagated through the center or near the center of a cross-section of specimens. This region was a segregated zone where the center segregation of elements has occurred. Finally, we recognized a linear correlation between the HIC susceptibility and hardness value in steel, where by moving away from the cracks (1800 µm) to the crack edges, the hardness value increased significantly (179–203 HV), confirming the diffusion of hydrogen into hydrogen traps.

A novel friction stir welding method called projection friction stir spot welding (PFSSW) was introduced to produce safe and reliable welds by using a pinless tool and a specially-designed projection on the surface of a backing anvil. This projection along with the tool rotation speed plays an important role in having a reliable joint with excellent mechanical properties and good surface appearance. This welding technique can be widely developed in oil and gas, as well as in automotive, aerospace, and transportation, industry. The effect of tool rotation speed (1000, 1600, 2000 rpm) on the hardness, microstructure, and mechanical properties of 2024 aluminum alloy sheets was investigated. The surface appearance of the welding zone showed that the keyhole was not formed, and the appearance of the weld was almost smooth. Fracture surfaces of the failed specimens present the interfacial fracture at the tool rotation speed of 1000 rpm and circumferential fracture at tool rotation speed of 1600 and 2000 rpm.

In this research, the rate of CO2 absorption into methyl diethanolamine–piperazine (MDEA–PZ) solution was investigated. To model the mass transfer flux in the reactive absorption processes, the dimensionless parameters of the process were obtained using the Buckingham Pi theorem and considering the effective parameters in mass transfer. The CO2 mass transfer flux in the reactive absorption process depends on the mass transfer parameters of both the liquid and gas phases. Based on the dimensionless parameters obtained, a correlation is proposed to calculate the mass transfer flux of acidic gases in MDEA–PZ solutions. The mass transfer flux in the reactive absorption process is modeled based on the four laws of chemical equilibrium, phase equilibrium, mass balance, and charge balance. Experimental data from the literature were used to determine the constants of the derived correlation as a function of dimensionless parameters. In the provided correlation, the effects of dimensionless parameters including film parameter, CO2 loading, ratio of diffusion coefficients in the gas–liquid phase, CO2 partial to total pressure, and film thickness ratio as well as factors such as temperature, the number of free amines in the solution, the partial pressure of CO2, on the CO2 mass transfer flux were investigated. According to the results, the absorption rate decreases with increasing CO2 loading and film parameter, and the mean absolute deviation is about 3.6%, which indicates the high accuracy of the correlation.

It is difficult to identify the carbonate reservoirs by using conventional seismic reflection data, especially in cases where the reflection coefficient of the gas-bearing zone is close to that of the carbonate background. In such cases, the extended elastic impedance (EEI) as a seismic reconnaissance attribute with the ability to predict fluids and lithology can be used. It allows for a better distinction between seismic anomaly caused by lithology and the one caused by the fluid content. The EEI attribute extends the available reflection angles and applies different weights to the intercept and gradient values so as to extract the petrophysical properties of the rock at a specific incident angle. Using the EEI attribute, we can estimate the elastic parameters such as shear impedance; the ratio of the compressional velocity to shear velocity; Poisson’s ratio; and bulk, Lame, and shear moduli, and petrophysical properties, including porosity, clay content, and water saturation. The known reservoirs in the study area are three oil-bearing formations namely, Surmeh (Arab), Gadvan (Buwaib), and Dariyan (Shuaiba), and three gas-bearing formations, including Kangan, Dalan, and Faraghan. The Dehram group is composed of Kangan (Triassic), Dalan, and Faraghan (Permian) formations. Permian carbonates of Kangan–Dalan and its equivalent Khuff have regionally been developed as a thick carbonate sequence in the southern Persian Gulf region. In this paper, parameters 𝜆𝑝 and 𝜇𝜌 extracted from the EEI method are used to characterize a carbonate reservoir. Our results show that the EEI can highlight the difference between the reservoir and non-reservoir formation to identify the gas-bearing areas.