Investigation of Slug Suppression System in Deepwater Scenario

In pipeline-riser systems, pressure fluctuations which result from the formation of large liquid slugs and gas surges due to operational changes or low mass flow rate from production wells and the profile of pipeline-riser systems often lead to trips at the inlet of the separator; and thereby, the problem causes a a loss of the production.In this study, on a sample deep-water oil field off the coast of West Africa is focused. The field lies in water depths greater than 1000 m. Moreover, the wells are connected via a pipeline-riser system to the topside. The slug suppression system (S3) was changed as a control structure on the field case study.S3 comprises of a mini separator coupled with dynamically controlled valves at the liquid and gas outlets. This control structure was modeled on OLGA, a one-dimensional, and two-fluid equations based commercial multiphase flow simulation tool. In implementing the S3, it was transformed into a parallel configuration of two proportional-integral (PI) controllers (the separator level and pressure controllers) which controls the total volumetric flow and liquid flow respectively by subsequent opening of the valves at the outlets while stabilizing the riser base pressure. In addition, separator sizing was based on the volume of multiphase fluid at the riser-top. Also, controller-tuning parameters were obtained from parametric studies with pressure and liquid level set point at 20.5 bar and 0.5 m.Finally, it is found out that S3 is able to stabilize the riser base pressure and flow rate at the outlet of the mini-separator. Moreover, the comparison of production rates before and after the implementation of the control structure indicated an increase of 12.5% in the production rate

Investigation of Slug Suppression System in Deepwater Scenario

In pipeline-riser systems, pressure fluctuations which result from the formation of large liquid slugs and gas surges due to operational changes or low mass flow rate from production wells and the profile of pipeline-riser systems often lead to trips at the inlet of the separator; and thereby, the problem causes a a loss of the production. In this study, on a sample deep-water oil field off the coast of West Africa is focused. The field lies in water depths greater than 1000 m. Moreover, the wells are connected via a pipeline-riser system to the topside. The slug suppression system (S 3 ) was changed as a control structure on the field case study. S 3 comprises of a mini separator coupled with dynamically controlled valves at the liquid and gas outlets. This control structure was modeled on OLGA, a one-dimensional, and two-fluid equations based commercial multiphase flow simulation tool. In implementing the S 3 , it was transformed into a parallel configuration of two proportional-integral (PI) controllers (the separator level and pressure controllers) which controls the total volumetric flow and liquid flow respectively by subsequent opening of the valves at the outlets while stabilizing the riser base pressure. In addition, separator sizing was based on the volume of multiphase fluid at the riser-top. Also, controller-tuning parameters were obtained from parametric studies with pressure and liquid level set point at 20.5 bar and 0.5 m. Finally, it is found out that S 3 is able to stabilize the riser base pressure and flow rate at the outlet of the mini-separator. Moreover, the comparison of production rates before and after the implementation of the control structure indicated an increase of 12.5% in the production rat

Turbulence modelling and role of compressibility on oil spilling from a damaged double hull tank

The viscosity plays an important role, and a multiphase solver is necessary to numerically simulate the oil spilling from a damaged double hull tank (DHT). However, it is uncertain whether turbulence modelling is necessary, which turbulence model is suitable; and what the role of compressibility of the fluids is. This paper presents experimental and numerical investigations to address these issues for various cases representing different scenarios of the oil spilling, including grounding and collision. In the numerical investigations, various approaches to model the turbulence, including the large eddy simulation (LES), direct numerical simulation and the Reynolds average Navier-Stokes equation (RANS) with different turbulence models, are employed. Based on the investigations, it is suggested that the effective Reynolds numbers corresponding to both oil outflow and water inflow shall be considered when classifying the significance of the turbulence and selecting the appropriate turbulence models. This is confirmed by new lab tests considering the axial offset between the internal and the external holes on two hulls of the DHT. The investigations conclude for numerically simulating oil spilling from a damaged DHT that when the effective Re is smaller the RANS approaches should not be used and LES modelling should be employed; while when the effective Reynolds numbers is large, the RANS models may be used as they can give similar results to LES in terms of the height of the mixture in the ballast tank and discharge but costing much less CPU time. The investigation on the role of the compressibility of the fluid reveals that the compressibility of the fluid may be considerable in a small temporal-spatial scale but plays an insignificant role on macroscopic process of the oil spilling

Effect of Temperature and Contamination on the Surface Tension of Niger Delta Crude Oils

Abstract: Surface tension is an important property that affects the behavior and characteristics of reservoir fluids.. It impacts the capillary pressure and fluid dynamics in porous media. This study, investigated the surface tension of Contaminated Niger Delta crude oil at varying temperatures. Laboratory tests were carried out on samples from four fields in the Niger Delta using DuNouy Tensiometer under standard conditions. The results show that for Niger Delta Crudes of gravity between 25 -49 API, Surface Tension varies between 25.8 -31.2 dynes/cm at 29 o C and decreases to between 21.5-26.6 dynes/cm at 90 o C. Surface Tension of the crudes was also affected by salt contamination, bentonite and mud filtrate and surfactant contamination. Contamination by bentonite also increased the surface tension from about 28 to 34 dynes/cm. predictive models have been developed as a quick-look tool for estimating surface tension of Niger Delta crude oil and similar reservoir fluids

Oilfield produced water assessment from onshore treatment facilities in Niger Delta: Water quality susceptibility and suitability for soil irrigation

The abundance of natural fossil fuel in the Niger Delta of Nigeria has instituted generation of oilfield produced water (PW) in large volume. This constitutes environmental pollution when discharged outside the permissible limit given by Nigerian Upstream Petroleum Regulatory Commission (NUPRC). PW can be used for soil irrigation if its constituents are remediated after treatment. This research assessed the physicochemical properties of untreated and treated samples of oilfield PW from Awoba, Imo River and Kolo creek oil fields of Niger Delta using electrometric, argentometric, colorimetric, titration, atomic absorption spectroscopy, APHA and HACH standard methods. Oil-treatment facilities effectiveness was investigated by comparing laboratory results for treated-PW with the permissible regulatory values of NUPRC. The pH, salinity hazard, sodium hazard, boron, chloride, TDS, carbonate and nitrate of treated-PW were measured to check the suitability of treated-PW quality for soil irrigation. Measured values were compared with the permissible standard of US EPA. Sodium adsorption ratio (SAR) and electric conductivity (EC) were used to determine the level of sodium and salinity hazards respectively. The results indicated that none of the untreated-PW samples complied with NUPRC permissible limit. Physicochemical properties of treated-PW revealed samples to be close to or within approved NUPRC standards except in few cases. All the measured parameters of treated-PW from Awoba and Imo River oil fields conformed to the US EPA standard value except their ECs and SAR of Imo River oil field which measured 2.46 and 2.93 ds m−1, and 2.57 respectively. However, all other parameters measured for treated-PW from Kolo creek oil field did not conform to the standard except pH and nitrate which measured 7.7 and 4.86 mg/L respectively. In conclusion, oil treatment facilities should be more robust to degrade a wide range of recalcitrant compounds in PW pollutants in order to minimize the impacts of toxic compounds in PW on the environment

Treatment of produced water from Niger Delta oil fields using simultaneous mixture of local materials

Abstract Produced water (PW) from petroleum reservoirs often contains heavy metals and other contaminants that are harmful to the environment. Most of the commonly used treatment techniques have been reported to be ineffective in reducing some of the contaminants’ concentrations to recommended disposal levels. This study evaluated the effectiveness of four selected bio-adsorbents combined for treating PW from Niger Delta oil fields. In this study, orange peels (I), banana peels (II), sponge gourd (Luffa cylindrica) (III) and palm kernel fibers (IV) were washed with distilled water, sun-dried (24 h) and dried in the oven at 105 ± 5 °C (3 h, I and II), 150 °C (30 min, III) and 80 °C (3 h, IV). They were ground into powder, sieved (150 μ, Group A) and (300 μ, Group B), washed with 0.4 mol/L HNO3, filtered and rinsed with distilled water. Samples of PW were obtained from fields R, X, and Y in the Niger Delta and analysed for heavy metals using an atomic absorption spectrophotometer (AAS). Samples were treated in adsorption column over 6 h using the adsorbents simultaneously. Treated samples were analysed with AAS and characterised. Adsorption of heavy metals were assessed using Langmuir and Freundlich models. Data were analysed using regression and other statistical methods. For the 150 μ size of sample R, the percentage reductions for the metal concentrations (Pb, Ni, Cd, Cu, Fe, Mg, Cr, Zn, Mn, Ca, Ar, B, Sn and Ba) were found to be 100%, 52.7%, 100%, 100%, 85.87%, 19.48%, 100%, 92.8%, 17.74%, 98.86%, 22.32%, 29.56%, 78.06% and 44.74%, respectively, while the reduction in 300 μ size were 1.52%, 97.2%, 71.4%, 17.1%, 43.8%, 45.6%, 7.04%, 89.6%, 35.4%, 99.6%, 0.0001%, 1.19%, 14.19% and 0.002%, respectively. The finer adsorbents were more effective. Similar results were obtained for PW samples from the other fields. Produced water from Niger Delta oil fields was effectively treated of contaminants using four selected bio-adsorbents mixed simultaneously