Real Oilfield Research Articles

Исследование эффективности методов постобработки потоков при решении задач многофазной фильтрации

Methods for post-processing of finite element solutions in the simulation of multiphase flows are considered. To simulate filtration processes, a special method based on the implicit calculation of the pressure field and the explicit calculation of saturations is used. Post-processing of flows is performed using two technologies - the balancing method and the projection method. The method of balancing the numerical flows of the mixture ensures the fulfillment of local conservation laws by finding corrections to the flows of the mixture calculated using the FEM. For the closeness of the modified mixture flows to the original numerical ones, the regularization parameters in the balancing method are calculated using the averaged unbalance. In the projection method, the balanced values of fluxes through the faces of finite elements are corrected by adding constant corrections (constant per element). Computational experiments were carried out on a test problem, a model of a field with a simple structure, and a model of a real oil field in the Republic of Tatarstan. When modeling problems with the appropriate correction of the known mixture flows on the faces of the wells, the solutions obtained using the balancing method and the projection method have little difference. The results of research on problems have shown that both technologies provide conservative solutions for which conservation laws are satisfied. At the same time, the use of the method of balancing the numerical flows of the mixture provides a higher accuracy than the projection method, when the flows in the wells are corrected in the post-processing process (that is, in fact, production/injection is emulated while maintaining a fixed pressure). The projection method can be improved by using the weight functions proposed for the balancing method. However, even in this case, the balancing method allows obtaining more accurate solutions.

Adsorption and photocatalytic degradation of oilfield produced water by visible-light driven superhydrophobic composite of MIL-101(Cr)/Fe3O4-SiO2: Synthesis, characterization and optimization

A visible-light driven superhydrophobic composite of MIL-101(Cr)/Fe3O4-SiO2 was synthesized via hydrothermal method. Various physicochemical techniques were employed for the characterization of the nanoparticles such as XRD, FTIR, FESEM, TEM, EDS, BET, UV–Visible DRS, PL, and pHpzc. The adsorption and photocatalytic performance of the synthesized nanoparticles were evaluated by synthetic and real oilfield produced water (OPW) treatment. The optimal loading amount of Fe3O4-SiO2 was determined by analysis tests and investigation of photocatalytic activity. The results showed that the superhydrophobic composite with 35% weight percent of Fe3O4-SiO2 exhibited the maximum removal efficiency. Effect of operational parameters such as pH, reaction time, and initial concentration of pollutants on the removal efficiency were evaluated. The chemical oxygen demand (COD) removal efficiency of synthetic oilfield produced water (SOPW) achieved 95.17% and 96.6% under visible and UV light irradiation by MIL-101(Cr)/Fe3O4-SiO2 (35%), at the optimum conditions of pH 4, photocatalyst dosage 0.5 g/L, COD initial concentration 600 mg/L, and illumination time 150 min. Moreover, the gas chromatography-mass spectroscopy (GC–MS) analysis results showed 97.7% and 99.2% removal efficiency of total petroleum hydrocarbons (TPH) for real and synthetic OPW, respectively. The results of kinetic and isotherm study showed that the kinetic data followed the pseudo-second-order and equilibrium adsorption was described by the Freundlich model. The high specific surface area, narrow bandgap energy as well as the charge carrier separation based on the Z-scheme heterostructure caused the improvement of binary composite photocatalyst features. The results demonstrated that the MIL-101(Cr)/Fe3O4-SiO2 superhydrophobic composite are promising photocatalyst in the degradation of oilfield produced water pollutants. Synergistic effect of adsorption and photocatalytic degradation of OPW help to enhance the removal performance.

A Continuous-Time-Based MILP Model for Production and Transportation Scheduling in Nonpipelined Wells in Low-Permeability Oil Fields

Abstract The marginal wells in low-permeability oilfields are characterized by small storage size, scattered distribution, large regional span, low production, intermittent production, etc. The production mode of these wells is nonpipeline mode. In our previous work (Zhang et al., 2019), a novel mixed-integer linear programming (MILP) model using a discrete-time representation was presented for the operation scheduling of nonpipelined wells. However, too many discretization time points are required to ensure the accuracy of the model. Even for moderately sized problems, computationally intractable models can arise. The present paper describes a new continuous-time representation method to reformulate this schedule optimization problem. By introducing the continuous-time representation, the binary variables are largely reduced. The solution effect for different model sizes is also investigated. When the model size increases to a certain degree, a feasible solution cannot be obtained within a limited time. The results of a case study originated from a real oilfield in China show that the continuous-time model requires less time to obtain the optimal solution compared to the discrete-time model. In details, considering a same scale problem, the solution based on the continuous-time model saves 52.25% of the time comparing with the discrete-time model. The comparison validates the new model’s superiority.

Efficient preparation of ultrathin ceramic wafer membranes for the high-effective treatment of the oilfield produced water

Efficient preparation of ceramic membranes helps to reduce costs and makes them more competitive in the field of wastewater treatment. In this work, an ultrathin Al2O3 ceramic wafer membrane with a thickness of 250 µm and the mean pore size of approximately 200 nm was prepared from the Al2O3/polysulfone slurries via a casting-phase inversion/sintering approach. This ultrathin and hydrophilic ceramic wafer has a fully sponge-like and slightly asymmetric structure and desirable porosity, endowing it with an exceptionally high pure water permeability of ∼ 45,000 L m-2h−1 bar−1, an ultrahigh and stable emulsion flux of 2500 ∼ 3500 L m-2h−1 bar−1, as well as a high oil rejection of 99 % against real oilfield produced water (OPW). In addition, the increased Al2O3 content enhanced the thermodynamic instability of the ceramic slurry, leading to the enhanced interfacial instability, which contributes to the uniform distribution of Al2O3 particles on the precursor membrane surface to some extent during the phase inversion process, thus to reduce the surface defects of ceramic membranes after sintering. The membrane fouling analysis revealed that the dominant fouling mechanism was cake filtration, indicating the formation of a relatively dense and smooth skin layer of the ceramic wafer, which endow it with a high flux recovery ratio of 97.8 % by a simple chemical cleaning after OPW filtration.

Reducing Drilling Hazard Risk in a Carbonate Environment Using Seismic Processing, Diffraction Imaging and Interpretation

Buried structural anomalies within carbonate depositional environments, such as karst sinkholes, impose significant dangers for borehole integrity and drilling equipment due to rapid changes in rock properties (from tight to the porous) potentially resulting in extensive mud loss, drill bit jamming and other complications. This often leads to delays in the well construction planning and sometimes to subsequent sidetrack drilling and a dramatic increase in costs. Thus, Paleo-karst localization, prior to well planning and construction, becomes a critical task for economic optimization. However, this is a non-trivial exercise due to the relatively small scale and size of karst type features and anomalies, which are at the limit of lateral resolution of most standard surface geophysical methods. In this paper, we introduce a methodology of karst prediction based on a combination of targeted 3D seismic processing and integration of the diffracted wavefield anomalies in addition to use of conventional seismic attributes. The presented approach has been proven to be efficient to detect karsts in a real oil field and can be deployed in other regions.

Treatment of oil-field produced wastewater by electron beam technology: Demulsification, disinfection and oil removal

The treatment of polymer-containing produced wastewater with high viscosity and emulsification is a challenging issue in the oilfield. In this paper, electron beam (EB) radiation technology was firstly applied to treat the real oilfield produced wastewater. The results showed that the viscosity of the produced wastewater decreased rapidly from initial 3.7 mPa s to 1.5 mPa s after EB radiation at absorbed dose of 1.0 kGy, then it gradually reached the level of pure water at 5.0 kGy. The produced wastewater was negatively charged and the absolute value of zeta potential diminished stepwise during EB radiation process, indicating that the stability of oil/water emulsion decreased. Radiation pretreatment contributed to the oil removal by coagulation. The efficiency of oil removal increased remarkably from 47% by coagulation alone to 85% with EB pretreatment at 1.0 kGy. Radiation is also effective to disinfect the three typical bacteria in oilfield wastewater, saprophytic bacteria (TGB), sulfate-reducing bacteria (SRB) and iron bacteria (IB). More than 99.8% of TGB, SRB and IB were killed at 1.0 kGy, and a complete inactivation was obtained at 2.5 kGy. Oxidation by ·OH radicals formed in water radiolysis is the major pathway to decrease the viscosity and kill the bacteria, while the direct action of EB radiation also plays a role. The members belonging to genera Thauera, Defluviimonas and Comamonadaceae were predominant in the produced wastewater, with a relative abundance of 40%, 19% and 16%. Based on PICRUSt analysis, the function genes related to metabolism exhibit the highest abundance (25%), which increased at 1.0 kGy, and then decreased at 10 kGy, suggesting that EB radiation at low dose might stimulate the bacterial activity.

Biokinetic Study of Microbial Decontamination of Oilfield Produced Water

This work was aimed at identifying microbials and determining the biokinetic parameters for bio-decontamination of oilfield produced water. An extant physical treatment unit for produced water was re-engineered and retrofit with a discontinuous aerobic bioreactor (Bio-Unit) system. The Bio-Unit was operated in a fill-and-draw sequence and the rates of total organic carbon (TOC) removal and biomass growth were monitored. The isolated microbial strains were identified as Bacillus, Pseudomonas and Chryseobacterium spp. The biokinetic parameters of the bio-detoxification process were determined by fitting experimental data into the Monod Equation. The maximum specific substrate utilization rate (k_m), maximum specific growth rate (μ(m,h )), substrate half saturation coefficient (K(STOC )), yield (Y), and endogenous decay rate (b_h), were found to be 0.20 day-1, 0.31 day-1, 2.7 mg TOC/l, 1.6 mg MLSS/mg TOC, and 0.23 day-1, respectively. These values are within the range published in literatures for oilfield produced water, thus will suffice for designing, modeling and control of biological treatment systems, since biokinetic parameters for real oilfield produced water treatment using discontinuous biological configuration is scanty.

Boron removal from synthetic brines and oilfield produced waters using aluminum electrocoagulation

High boron (B) levels in oil and gas produced waters prevent its beneficial reuse as irrigation water without proper treatment. Aluminum (Al) electrocoagulation (EC) is a promising technology for B removal, but further research and development is needed to optimize EC for use in removing B from produced waters. To this end, B removal by adsorption onto insoluble aluminum hydroxide solids, generated by EC in simulated brines (up to 50,000 mg/L NaCl) and real oilfield produced waters, was studied. B removal during EC was greater than when aluminum hydroxide solids formed by EC were subsequently exposed to B containing solutions. Working parameters affecting B removal during the EC process, including current, total dissolved solid (TDS), temperature, pH, scale-forming cations and organic matter, were investigated to explore ways to achieve higher B removal. Boron removal increased with increased current loading and time, and with the concomitant increased Al solids concentration. However, too high a current loading limited B removal because of a change in the structure of the aluminum hydroxide solids. Higher TDS decreased B removal slightly, but lower TDS concentrations limited the use of higher current loadings. Temperature increased during EC treatment, particularly at higher current loadings, and this inhibited B removal due to an accelerated aggregation of amorphous Al solids into larger, denser, and presumably more crystalline particles. The best B removal occurred at pH 8, corresponding to a slightly positive zeta potential for aluminum hydroxide and a small but significant fraction of negatively charged B species. Scale-forming cations such as Ba2+ and Sr2+ had no obvious effect on the EC process. The presence of high concentrations of Mg2+ and Ca2+ resulted in low bulk pH values during the EC process and greater formation of solid products, but B removal did not decrease during a pH-controlled (pH = 8) EC process with these divalent cations present. Two produced water samples collected from oilfields in Kansas, US were treated using EC for 1 h, resulting in up to ~70 % B removal from solution with a current loading of 6.67 A/L, and up to 78 % with 13.33 A/L.

Prediction of Oil Saturation during Water and Gas Injection Using Controllable Convolutional Long Short-Term Memory

Oil saturation is a kind of spatiotemporal sequence that changes dynamically with time, and it is affected not only by the reservoir properties, but also by the injection–production parameters. When predicting oil saturation during water and gas injection, the influence of time, space and injection–production parameters should be considered. Aiming at this issue, a prediction method based on a controllable convolutional long short-term memory network (Ctrl-CLSTM) is proposed in this paper. The Ctrl-CLSTM is an unsupervised learning model whose input is the previous spatiotemporal sequence together with the controllable factors of corresponding moments, and the output is the sequence to be predicted. In this way, future oil saturation can be generated from the historical context. Concretely, the convolution operation is embedded into each unit to describe the interaction between temporal features and spatial structures of oil saturation, thus the Ctrl-CLSTM realizes the unified modeling of the spatiotemporal features of oil saturation. In addition, a novel control gate structure is introduced in each Ctrl-CLSTM unit to take the injection–production parameters as controllable influencing factors and establish the nonlinear relationship between oil saturation and injection–production parameters according to the coordinates of each well location. Therefore, different oil saturation prediction results can be obtained by changing the injection–production parameters. Finally, experiments on real oilfields show that the Ctrl-CLSTM comprehensively considers the influence of artificial controllable factors such as injection–production parameters, accomplishes accurate prediction of oil saturation with a structure similarity of more than 98% and is more time efficient than reservoir numerical simulation.

Numerical simulation and field application of biological nano-technology in the low- and medium-permeability reservoirs of an offshore oilfield

As a result of deep burial depth, small pore throat, poor connectivity between pores, different clay mineral contents in reservoirs, and strong reservoir sensitivity, injection wells often have problems such as rapidly increasing water-injection pressure and insufficient water-injection quantity in the process of water-injection development. The main measures used to solve the difficulties of water injection in low-permeability reservoirs include fracturing, acidizing, and surfactant depressurization and injection increase, all of which have some disadvantages of high cost and environmental damage. In recent years, depressurization and injection-increase environment-safe bio-nano-materials have been introduced into low-permeability reservoirs and have achieved good application results in China. On the other hand, although there have been many researches on EOR (enhanced oil recovery) of nano-materials, the numerical simulation field of nano-depressurization and injection-augmenting technology is still a blank that the wettability mechanism of nano-materials and EOR nano-materials used in bio-nano-depressurization and injection-augmenting technology are almost completely opposite, and the influence of adsorption on formation is almost completely opposite. The adsorption of nanoparticles in other EOR studies will reduce the porosity and make the reservoir more hydrophilic. Nanoparticles used in biological nano-technology will produce hydrophobic film near the well, which will reduce the seepage resistance through the slip of water phase. In this study, a set of water flooding model of numerical simulation technology for depressurization and injection-augmenting of biological nano-materials considering adsorption characteristics and reservoir physical properties was established, the sensitivity analysis of key injection parameters was carried out, and the application effect prediction chart of biological nano-technology was drawn, and the model and prediction chart were verified by real oilfield data. As far as we know, this is the first numerical simulation study on biological nano-technology that has been applied in oil fields.

Proxy Capacitance-Resistance Modeling for Well Production Forecasts in Case of Well Treatments

Summary We disclose a new-age field-scale production forecast model that handles complex treatment of wellbores during their life cycle. Predictive production models have been an object of increased interest and research for a long time due to the need for a fast tool for forecasting production rates or choosing an optimal field development scheme. The existing approaches based on the material balance equation have several limitations and are not very applicable for real objects. Full-scale reservoir modeling is relatively slow and requires large computing resources. In this paper, we propose a proxy model based on advanced capacitance-resistance approach. The model predicts multiphase flow rates based on the available historical data of field production and information about well treatments. In addition, it provides preferable transmissibility trends, the presence of sealed or leaking faults, and the degree of dissipation between injector-producer well pairs. The advanced feature of the model is time-dependent weight coefficients, which have not been studied previously. They help in accounting the shut-in and workover periods and can be found during the optimization procedure simultaneously. Another feature is fast calculations due to a vectorized form of the model and application of modern optimization techniques. All these options allow modeling real oil fields with a large number of wells and a complex system of production control.

A New Kinetic Assay Method for Effective Scale Inhibitor Concentration Determination with Low Detection Limit

Summary Scale inhibitors are widely used for mineral scale control in various industries, including oil and gas productions, geothermal energy acquisitions, and heat exchanger scale control to mention a few. In most applications, these scale inhibitors are effective at substoichiometric concentrations (e.g., 1 mg/L or lower), and the optimization of these applications is based on the ability to accurately measure the effective inhibitor concentration at such low concentrations. For example, the continuous treatment injection rate, the squeeze treatment frequency, or the batch treatment schedule need to be optimized to ensure the minimum inhibitor concentration (MIC) is achieved during production. However, the non- or low-phosphorous polymeric scale inhibitor concentration determination is difficult using inductively coupled plasma (ICP)-optic emission spectroscopy/mass spectrometry or ion chromatography, especially at mg/L level concentrations due to their high detection limits. The recently developed hyamine method or high-pressure liquid chromatography (HPLC) method involves intensive labor and high costs. Furthermore, in the complex oilfield operational conditions, the presence of other chemicals (e.g., surfactants, biocides, and corrosion inhibitors), the potential degradation of scale inhibitors and the use of combination scale inhibitors require the measurement of effective scale inhibitor concentration, which cannot be accomplished by the traditional methods. In this study, a new kinetic assay method has been developed to determine the effective scale inhibitor concentration with limits of detection (LODs) less than or around 0.1 mg/L for most cases. This method uses a continuous stirring tank reactor (CSTR) apparatus and is developed based on the linear correlation between the effective inhibition concentration and the measured critical time when laser signal changes. The results show that the inhibitor concentrations of various non- or low-phosphorous polymeric scale inhibitors in synthetic field brine, laboratory solutions, and real oilfield brines can be accurately determined at mg/L level, or lower, with less than 10% error. The method is robust, accurate, and much less time- or labor-consuming than other existing methods especially for non- or low-phosphorous polymeric scale inhibitors.

Evaluation of petroleum as extractor fluid in liquid-liquid extraction to reduce the oil and grease content of oilfield produced water

This work aims to evaluate the use of petroleum as a solvent in the liquid-liquid extraction of oil and grease content from oilfied produced water. Initially, tests were performed with synthetic effluent, using cyclohexanecarboxylic acid as model compound through the study of physical-chemical parameters: pH, temperature, stirring speed and time, petroleum type and concentration, and initial concentration of naphthenic acids. Afterwards, the process was evaluated for the removal of oil and grease content from a real oilfield produced water sample. The pH and petroleum concentration proved to be significantly influential in removing cyclohexanecarboxylic acid from the synthetic produced water (ANOVA). The greater the amount of petroleum present, the greater the efficiency. By acidifying the synthetic effluent, the efficiency of removing these naphthenic acids from the synthetic produced water was increased. Response surface methodology (RSM) evaluated these two factors. On the other hand, the initial concentration of cyclohexanecarboxylic acid and petroleum type did not presented great influence on the obtained results, indicating robustness of the process. The methodology carried out with synthetic effluent proved to be efficient in removing the oil and grease content from real effluent (≈ 60% of removal at pH range 2–5).

Вычислительная схема для расчета температурного поля при решении задач нефтедобычи

The paper presents an approach to coupled modeling of hydrodynamic and thermal processes occurring in the oil reservoir during field development using thermal methods of enhanced oil recovery. To simulate the processes of non-isothermal multiphase flow, an approach based on implicit calculation of pressure using the finite element method and an explicit calculation of phase saturations is used. A computational scheme for calculating the temperature field is considered. This scheme makes it possible to take into account both heat transfer between phases and heat transfer of a fluid mixture and matrix-rock. In order to take into account the effect of thermal conductivity, a coefficient characterizing the rate of heat transfer between the fluid mixture and the rock is used. The proposed scheme also takes into account the effect of the temperature field on the phases flow in the field reservoir and provides for the possibility of heat sources and sinks occured due to chemical reactions or thermodynamic processes in gaseous phases. Numerical experiments were carried out on a model of a real oil field obtained as a result of history matching of well data. The model contains a large number of wells and is characterized by a high heterogeneity of the porous medium. The applicability of the considered computational scheme is demonstrated on the example of modeling hot water injection into wells crossing a formation with super-viscous oil. The efficiency of thermal methods for the development of super-viscous oil fields is shown. When hot water was injected into the reservoir, the increase in oil production was about 25 % due to a significant decrease in oil viscosity. The time spent for calculating the temperature field while simulating a multiphase flow did not exceed 6 % of the total computational time.

MEDIUM FOR LOCAL CO2-CORROSION LABORATORY TESTING

The results of laboratory experiments are presented, in which the essential features of corrosion processes occurring in real oilfield systems are simulated, namely, a high rate of local corrosion, exceeding the corrosion rate by 2…9 times. A standard environment and conditions for laboratory experiments are proposed, which make it possible to reproduce visible and measured with a needle micrometer (> 0,01 mm) local corrosion damage on coupons of corrosion control by the gravimetric method. The protective effect of corrosion inhibitors in relation to local carbon dioxide corrosion at the selected dosage is proposed to be assessed not by the magnitude of the protective effect, but by the presence or absence of local corrosion on the coupons of corrosion control by the gravimetric method after the end of the test. It is shown that with a high protective effect of corrosion inhibitors in relation to corrosion rate, there may be no protective effect in relation to local corrosion.

Semi-Implicit Finite Volume Procedure for Compositional Subsurface Flow Simulation in Highly Anisotropic Porous Media

Subsurface multiphase flow in porous media simulation is extensively used in many disciplines. Large meshes with non-orthogonalities (e.g., corner point geometries) and full tensor highly anisotropy ratios are usually required for subsurface flow applications. Nonetheless, simulations using two-point flux approximations (TPFA) fail to accurately calculate fluxes in these types of meshes. Several simulators account for non-orthogonal meshes, but their discretization method is usually non-conservative. In this work, we propose a semi-implicit procedure for general compositional flow simulation in highly anisotropic porous media as an extension of TPFA. This procedure accounts for non-orthogonalities by adding corrections to residual in the Newton-Raphson method. Our semi-implicit formulation poses the guideline for FlowTraM (Flow and Transport Modeller) implementation for research and industry subsurface purposes. We validated FlowTraM with a non-orthogonal variation of the Third SPE Comparative Solution Project case. Our model is used to successfully simulating a real Colombian oil field.

Simultaneous Control of Formation and Growth of Asphaltene Solids and Wax Crystals Using Single-Walled Carbon Nanotubes: an Experimental Study under Real Oilfield Conditions

Asphaltene and wax depositions in oil production systems have been recognized as the most serious flow assurance concern of petroleum engineering. Despite the several chemicals offered for treatment of issues induced by these organic deposits, proposing a single efficient chemical to control simultaneously both asphaltene and wax precipitation has not been attended yet. Here, single-walled carbon nanotubes (SWCNTs) were synthesized to assess their effects on controlling the formation and size growth of asphaltene particles and wax crystals in live oil under realistic production conditions. SDS experiments showed that during depressurization at 125 °C, the asphaltene onset pressure decreased from 5946 psi in untreated live oil to 4375 in treated live oil with 100 ppm SWCNTs. High-pressure microscopy revealed that SWCNTs efficiently controlled the growth of asphaltene aggregates and reduced the size of asphaltenes in live oil during depressurization at 125 °C. This is ascribed to the strong π–π interactions between the aromatic rings of SWCNTs and electron clouds of asphaltenes. Results of cross-polarized microscopy showed that SWCNTs at an optimum concentration of 75 ppm postponed the wax formation temperature and gelation point from 32.6 and 21.5 °C to 23.2 and 14.7 °C, respectively. In addition, the morphology of the wax crystals with an average size of 756 nm in untreated oil changed from dense spherical-like into thin needle-like with an average size of 86 nm in treated oil with SWCNTs at 75 ppm. The changes in the wax crystal size and structure via X-ray powder diffraction analysis after crude oil treatment with SWCNTs confirm interactions between the carbon nanotubes and active sites of the wax crystals. The findings of this research prove that synthesized carbon nanotubes can be used as efficient inhibitor and dispersant agents for stabilizing the waxes and asphaltenes in live oil with controlling the rate of aggregation under high-pressure–high-temperature conditions.

Electro-activated persulfate oxidation (EC/PS) for the treatment of real oilfield produced water: Optimization, developed numerical kinetic model, and comparison with thermal/EC/PS and EC systems

In this study, the performance and efficiency of electrocoagulation (EC), electro-activation of persulfate (EC/PS), and thermal activated-EC/PS for the treatment of two real produced water (PW) samples using iron electrodes were studied. To optimize and find out the effect of operating conditions on the different responses for EC and EC/PS, response surface methodology (RSM) was implemented. The results showed that EC process had considerable performance in the removal of H2S (96 %), oil and grease (O&G) (98–99 %), turbidity (91–97 %), phosphate phosphors (94 %), and heavy metals (92 %). EC/PS was introduced as an effective and a compact method for the removal of soluble hydrocarbons and nitrogen-ammonium (N-NH4+). The results indicated that at the current density of 35 A/m2, PS of 30 mM, reaction time of 30 min, N-NH4+ and chemical oxygen demand (COD) removal efficiency increased to 37 % and 71–94 %, respectively. To further increase the ammonia removal, EC/PS was integrated into thermal-PS activation at 65 °C, and the results showed that the ammonia removal by thermal/EC/PS reached about 69 %. According to gas chromatography/mass spectrometry (GC/MS), EC/PS was able to effectively eliminate most of the hydrocarbons. Moreover, a new kinetic model based on a novel algorithm and the main reactions occurring during EC/PS was developed to predict the COD removal efficiency, and the results indicated that it could predict COD removal efficiency with the acceptable accuracy. The estimated operating costs and energy consumption for EC/PS demonstrated that this process was more economical and efficient than other advanced oxidation processes (AOPs).

Technical and Economic Feasibility Study for Implementing a Novel Mooring-Assisting Methodology in Offloading Operations Using Autonomous Unmanned Aerial Vehicles

Summary As oil and gas exploration goes toward deeper fields in the Brazilian industry scenario, offloading operations emerge as the most viable option to drain production. However, these operations demand expensive resources, such as shuttle tankers and support boats; operational risks, which despite being managed, limited, and mitigated to be as low as reasonably possible, are still present in some stages (i.e., ship’s approximation to the oil rig, mooring, hose connection, and so forth); and environment limiting parameters (i.e., wave height, surface-current direction, wind speed and direction, and so forth). Therefore, in this paper, we propose using unmanned aerial vehicles (UAVs) in an autonomous mode to carry out the messenger line from the shuttle tanker to the floating, production, storage, and offloading (FPSO) unit or the floating storage and offloading unit (FSO) instead of line-handling (LH) boats (for conventional operations that use those resources) or the messenger-cable-launching guns (for dynamic positioning operations). This represents a viable alternative solution to reducing costs and risks in these tasks and a possibility to eliminate some meteorologic and oceanographic limiting conditions to operations, because the UAV will be susceptible only to wind conditions, and not to sea and visibility conditions, like LHs are. We present the simulated results of the proposed methodology using a robotic operating system (ROS) and the economic gain [derived from cash-flow-cost reducing of operations, payoff time of the investment, net present value (NPV), and internal rate of return] of applying this technology, evaluating its use in a realistic scenario based on a real deepwater oil field in Brazil. The developed controller behaves very well, and simulations showed robust results. In addition, the economic study presents the proposal’s attractiveness.

Boolean Spectral Analysis in Categorical Reservoir Modeling

This work introduces a new method for simulating facies distribution with two categories based on Fourier analysis of Boolean functions. According to this method, two categories of facies distributed along vertical wells are encoded as Boolean functions taking two values. The subsequent simulation process is divided into three consecutive steps. First, Boolean functions of the well data are decomposed into a binary version of a Fourier series. Decomposition coefficients are then simulated over the two-dimensional area as stationary random fields. Finally, synthetic data in the interwell space are reconstructed from simulated coefficients. The described method was implemented experimentally in software and tested on a case of a real oil field and on a case of a synthetic oil field model. Simulations on the synthetic model were used to test the performance of the method for two different bases in the Fourier expansion (Walsh functions and Haar wavelets). The simulation results were compared to those obtained on the same synthetic model via the classical sequential indicator simulation. It was shown that, for both bases, the new method reproduces statistical parameters of the well data better than sequential indicator simulation.