Fluxo de fluído através de um meio poroso fractal desordenado. Análise das tensões de cisalhamento e efeito de escala na estimativa das forças viscosas

In this work we have investigated some aspects of the two-dimensional flow of a viscous Newtonian fluid through a disordered porous medium modeled by a random fractal system similar to the Sierpinski carpet. This fractal is formed by obstacles of various sizes, whose distribution function follows a power law. They are randomly disposed in a rectangular channel. The velocity field and other details of fluid dynamics are obtained by solving numerically of the Navier-Stokes and continuity equations at the pore level, where occurs actually the flow of fluids in porous media. The results of numerical simulations allowed us to analyze the distribution of shear stresses developed in the solid-fluid interfaces, and find algebraic relations between the viscous forces or of friction with the geometric parameters of the model, including its fractal dimension. Based on the numerical results, we proposed scaling relations involving the relevant parameters of the phenomenon, allowing quantifying the fractions of these forces with respect to size classes of obstacles. Finally, it was also possible to make inferences about the fluctuations in the form of the distribution of viscous stresses developed on the surface of obstacles.

Avaliação do controle da diagênese na qualidade de reservatório siliciclástico do cenomaniano superior da formação Açu, sudoeste da bacia potiguar

The distribution of diagenetic alterations in Late Cenomanian siliciclastic reservoirs from Potiguar Basin was influenced by the stratigraphic framework and the depositional system. Seismic sections and geophysical logs of two wells drilled in the SW portion of the mentioned basin above register regional stratigraphic surfaces representing maximum floods related to a transgressive event. The sequential analysis of 80 m of drill core (~450 m deep) recognized nine depositional facies with an upwards granodecrescent standard piling that limits cycles with an erosional conglomeratic base (lag) overlain by intercalations of medium to very fine sandstones showing cross bedding (channel, planar and low angled) and horizontal bedding (plane-parallel , wave and flaser). The top of the cycles is marked by the deposition of pelites and the development of paleosoils and lagoons. The correlation of genetically related facies reveals associations of channel fillings, crevasse, and flood plains deposited in a transgressive system. Detailed descriptions of seventy nine thin sections aided by MEV-EBSD/EDS, DRX and stable isotope analyses in sandstones revealed an arcosian composition and complex textural arrays with abundant smectite fringes continuously covering primary components, mechanically infiltrated cuticles and moldic and intragrain pores. K-feldspar epitaxial overgrowth covers microcline and orthoclase grains before any other phase. Abundant pseudomatrix due to the compactation of mud intraclasts concentrate along the stratification planes, locally replaced by macrocristalline calcite and microcrystalline and framboidal pyrite. Kaolinite (booklets and vermicular), microcrystalline smectite, microcrystalline titanium minerals and pyrite replace the primary components. The intergrain porosity prevails over the moldic, intragrain and contraction porosities. The pores are poorly connected due to the presence of intergranular smectite, k-feldspar overgrowth, infiltrated mud and pseudomatrix. The sandstones were subjected to eodiagenetic conditions next to the surface and shallow burial mesodiagenetic conditions. The diagenetic alterations reduced the porosity and the permeability mainly due to the precipitation of smectite fringes, compactation of mud intraclasts onto the pseudomatrix and cementing by poikilotopic calcite characterizing different reservoir petrofacies. These diagenetic products acted as barriers and detours to the flow of fluids thus reducing the quality of the reservoir.

Estudo do tratamento sequencial (adsorção e eletro-oxidação) para remediação de efluente sintético contaminado com BTX

This paper proposed the study of the treatment of a synthetic wastewater contaminated with BTX by electro-oxidation batch with the anode of Ti/PbO2, and the adsorption of BTX using expanded perlite as adsorbent material, and to evaluate the best operating conditions both methods in order to perform a sequential treatment (adsorption and electro-oxidation) and achieve greater efficiency in the removal of the compounds. The operating conditions were measured: temperature, current density and applied amount of the adsorbent material, by UV-VIS analysis and Demand Chemical oxygen demand (COD). According to the experimental results, the electro-oxidative treatment was efficient in the degradation of the compounds BTX (benzene, toluene and xylenes) in synthetic sewage due to the electrochemical properties of the anode of Ti/PbO2. The applied current density and temperature promoted increased efficiency of COD removal, reaching obtain percentages greater than 70%. In the adsorption process, the temperature increase was not a factor in the removal of organic matter, while the increase in the amount of adsorbent material led to an increase in the percentage removal, obtaining 66.30% using 2 g of adsorbent. The selected operating conditions of both treatments performed separately take into account the removal efficiency of organic matter, and the low energy consumption and operating costs, so the sequential treatment were satisfactory reaching 87.26% of COD removal using adsorption as a pretreatment. Quantification of BTX through the analysis of gas chromatography at the end of the treatments also confirmed the removal efficiency of organic compounds, giving outstanding advantages to sequential treatment.

Petrologia das fraturas associadas a feições típicas de dissolução hipogênica na Formação Salitre, Bacia de Irecê, Bahia, Brasil

The recognition of karst reservoirs in carbonate rocks has become increasingly common. However, most karst features are small to be recognized in seismic sections or larger than expected to be investigated with borehole data. One way forward has been the study of analogue outcrops and caves. The present study investigates lithofacies and karst processes, which lead to the generation of the largest system of caves in South America. The study area is located in the Neoproterozoic Una Group in central-eastern Brazil. This province comprises several systems of carbonate caves (Karmann and Sanchéz, 1979), which include the Toca da Boa Vista and Barriguda caves, considered the largest caves in South America (Auler and Smart, 2003). These caves were formed mainly in dolomites of the Salitre Formation, which was deposited in a shallow marine environment in an epicontinental sea (Medeiros and Pereira, 1994). The Salitre Formation in the cave area comprises laminated mud/wakestones, intraclastic grainstones, oncolitic grainstones, oolitic grainstones, microbial laminites, colunar stromatolites, trombolites and fine siliciclastic rocks (marls, shales, and siltites). A thin layer and chert nodules also occur at the top of the carbonate unit. Phosphate deposits are also found. Our preliminary data indicate that folds and associated joints control the main karstification event at the end of the Brasiliano orogeny (740-540 Ma). We recognized five lithofacies in the cave system: (1) Bottom layers of grainstone with cross bedding comprise the main unit affected by speleogenesis, (2) thin grainstone layers with thin siltite layers, (3) microbial laminites layers, (4) layers of columnar stromatolites, and a (5) top layer of siltite. Levels (1) to (3) are affected by intense fracturing, whereas levels (4) and (5) seal the caves and have little fracturing. Chert, calcite and gipsite veins cut across the carbonate units and play a major role in diagenesis. Our preliminary study indicate that hypogenic spelogenesis is the main process of karst development and contributed significantly to the generation of secondary porosity and permeability in the carbonate units.

Estudo de simulação de reservatórios para o desenvolvimento de um campo do nordeste brasileiro

In the last 16 years emerged in Brazil a segment of independent producers with focus on onshore basins and shallow waters. Among the challenges of these companies is the development of fields with projects with a low net present value (NPV). The objective of this work was to study the technical-economical best option to develop an oil field in the Brazilian Northeast using reservoir simulation. Real geology, reservoir and production data was used to build the geological and simulation model. Due to not having PVT analysis, distillation method test data known as the true boiling points (TBP) were used to create a fluids model generating the PVT data. After execution of the history match, four development scenarios were simulated: the extrapolation of production without new investments, the conversion of a producing well for immiscible gas injection, the drilling of a vertical well and the drilling of a horizontal well. As a result, from the financial point of view, the gas injection is the alternative with lower added value, but it may be viable if there are environmental or regulatory restrictions to flaring or venting the produced gas into the atmosphere from this field or neighboring accumulations. The recovery factor achieved with the drilling of vertical and horizontal wells is similar, but the horizontal well is a project of production acceleration; therefore, the present incremental cumulative production with a minimum rate of company's attractiveness is higher. Depending on the crude oil Brent price and the drilling cost, this option can be technically and financially viable.

Modelagem matemática e experimental da perda de injetividade em poços canhoneados

Water injection in oil reservoirs is a recovery technique widely used for oil recovery. However, the injected water contains suspended particles that can be trapped, causing formation damage and injectivity decline. In such cases, it is necessary to stimulate the damaged formation looking forward to restore the injectivity of the injection wells. Injectivity decline causes a major negative impact to the economy of oil production, which is why, it is important to foresee the injectivity behavior for a good waterflooding management project. Mathematical models for injectivity losses allow studying the effect of the injected water quality, also the well and formation characteristics. Therefore, a mathematical model of injectivity losses for perforated injection wells was developed. The scientific novelty of this work relates to the modeling and prediction of injectivity decline in perforated injection wells, considering deep filtration and the formation of external cake in spheroidal perforations. The classic modeling for deep filtration was rewritten using spheroidal coordinates. The solution to the concentration of suspended particles was obtained analytically and the concentration of the retained particles, which cause formation damage, was solved numerically. The acquisition of the solution to impedance assumed a constant injection rate and the modified Darcy´s Law, defined as being the inverse of the normalized injectivity by the inverse of the initial injectivity. Finally, classic linear flow injectivity tests were performed within Berea sandstone samples, and within perforated samples. The parameters of the model, filtration and formation damage coefficients, obtained from the data, were used to verify the proposed modeling. The simulations showed a good fit to the experimental data, it was observed that the ratio between the particle size and pore has a large influence on the behavior of injectivity decline.

Análise comparativa de diferentes configurações de poços no processo de combustão in-situ

With an increasing number of mature fields, heavy oil recovery has performed one of the great challenges of the oil industry. The Brazilian Northeast, for example, has numerous heavy oil reservoirs are explored with the use of thermal methods. Among the types of methods used for heavy oil, there is the method of in-situ combustion, a technique in which heat is produced within the container, unlike the injection of heated fluid when the heat is generated at the surface and transported to the reservoir. In this type of process, it is common to use vertical wells as injectors and producers. However, methods which use horizontal wells like oil producers are increasingly studied because of greater contact area between the formation and combustion front. Thus, the main objective of this work was to study the different configurations of wells (CIS THAITM and CAGD) in the process of in-situ combustion in oil recovery using a semi-synthetic tank with Brazilian Northeast features. The method "toe-to-heel air injection" (THAITM) is a process of enhanced oil recovery, which is the integration of in-situ combustion with technological advances in drilling horizontal wells. This method uses horizontal wells such as oil producers, keeping vertical injection wells for injecting air. The oil drain process by differential gravitational assisted with combustion (CAGD) is an integrated, in this configuration the horizontal injector well is drilled at the top formation with a horizontal production well in the lower section. The simulations were performed in a commercial program of thermal processes, called "STARS" (Steam, Thermal, and Advanced Processes Reservoir Simulator), the company CMG (Computer Modelling Group). An analysis of the air flow injection was performed and it was found that each method had a maximum injection to the base model, a show that through this air injection limit was reduced cumulative production of oil. Analyses of operating parameters were used: injection flow, configuration and completion of wells. In the sensitivity analysis we found that the air injection flow showed greater influence on THAI method, since the CIS method the completion of the wells was the most influential parameter and CAGD configuration wells showed the greatest influence in the recovered fraction. The economic results have shown that the best case obtained in CAGD method because, despite having higher initial cost showed the best financial return compared to the best cases the CIS and THAI.

Análise comparativa de diferentes configurações de poços no processo de combustão in-situ

With an increasing number of mature fields, heavy oil recovery has performed one of the great challenges of the oil industry. The Brazilian Northeast, for example, has numerous heavy oil reservoirs are explored with the use of thermal methods. Among the types of methods used for heavy oil, there is the method of in-situ combustion, a technique in which heat is produced within the container, unlike the injection of heated fluid when the heat is generated at the surface and transported to the reservoir. In this type of process, it is common to use vertical wells as injectors and producers. However, methods which use horizontal wells like oil producers are increasingly studied because of greater contact area between the formation and combustion front. Thus, the main objective of this work was to study the different configurations of wells (CIS THAITM and CAGD) in the process of in-situ combustion in oil recovery using a semi-synthetic tank with Brazilian Northeast features. The method "toe-to-heel air injection" (THAITM) is a process of enhanced oil recovery, which is the integration of in-situ combustion with technological advances in drilling horizontal wells. This method uses horizontal wells such as oil producers, keeping vertical injection wells for injecting air. The oil drain process by differential gravitational assisted with combustion (CAGD) is an integrated, in this configuration the horizontal injector well is drilled at the top formation with a horizontal production well in the lower section. The simulations were performed in a commercial program of thermal processes, called "STARS" (Steam, Thermal, and Advanced Processes Reservoir Simulator), the company CMG (Computer Modelling Group). An analysis of the air flow injection was performed and it was found that each method had a maximum injection to the base model, a show that through this air injection limit was reduced cumulative production of oil. Analyses of operating parameters were used: injection flow, configuration and completion of wells. In the sensitivity analysis we found that the air injection flow showed greater influence on THAI method, since the CIS method the completion of the wells was the most influential parameter and CAGD configuration wells showed the greatest influence in the recovered fraction. The economic results have shown that the best case obtained in CAGD method because, despite having higher initial cost showed the best financial return compared to the best cases the CIS and THAI.

Estudo da eficiência dos adsorventes de Al2O3 e Fe/Al2O3 para remoção de BTX presente em água contaminada com gasolina

Contamination of groundwater by BTX has been featured in recent decades. This type of contamination is due to small and continuous leaks at gas stations, causing serious problems to public health and the environment. Based on these antecedents, the search for new alternatives for treating contaminated water is shown to be essential. Therefore, this study aimed to evaluate the efficiency of removal of BTX by adsorption processes employing commercial alumina (Al2O3) and alumina supported with iron (Fe/Al2O3) as adsorbents. It was prepared by a in a synthetic gasoline solution and distilled water to simulate an actual sample. Initially, the adsorbents were characterized by techniques XRD, TG / DTG, XRF, FTIR and SEM/EDS, several trials, where he was placed synthetic solution to react in the presence of Al2O3 and Fe/Al2O3 in a closed, mechanical stirring system were performed varying the catalyst concentration 2, 4 and 6 g.L-1 every 0, 10, 30 60, 90 and 120 min, aliquots were taken and brought to analysis by gas chromatography flame ionization with headspace extraction. The results indicated that the absorbent which has higher BTX removal capacity was the Fe/Al2O3 at a concentration of 6 g.L-1, pH = 4 and time of 90 minutes reaction, resulting in an efficiency, resulting in a 86,5% efficiency for benzene removal, for the 95,4% toluene, 90,8% for ɱ,ρ- xylene and 93.7% for the θ-xylenes. Subsequently, we performed a kinetic study of the reactions, the values of experimental adsorption capacity (qe) showed agreement with the values of the theoretical adsorption capacity (qc) to the pseudo-second-order model in the adsorption tests using 2 and 6 gL-1 of Al2O3 and assays using 2, 4 and 6 g.L-1 of Fe/Al2O3. A fact corroborated by the R2 values, thus indicating that the chemical interactions are present in the adsorption mechanisms of BTX.

Estudo da injeção de água e gás em um reservatório com características do pré-sal brasileiro

The pre-salt province is composed by large amounts of light oil and with good quality, a reality that puts Brazil in a strategic position facing the great demand for energy worldwide. In this province are the largest discoveries in the world in the last ten years; areas as Libra, Franco and Lula field, everyone containing volumes greater than 8 billion recoverable oil barrels. To develop and optimize the production of these fields, a study was done for choosing the improved oil recovery methods. The main motivations were the presence of carbon dioxide (CO2) as a contaminant and the strategic decision of do not discard it, combined with high GOR (gas-oil ratio) of the reservoir fluid. The method should take advantage of the unique abundant resources: seawater and produced gas. This way, the process of matching these resources in the water alterning gas injection (WAG) became a good option. In this master’s dissertation, it was developed a reservoir model with average characteristics of the Brazilian pre-salt, where was applied the improved oil recovery method of water alternating gas. The production of this reservoir was analyzed by parameters as: the first fluid injected in the injection process, position of the injection wells completion, injection water and gas rate and cycle time. The results showed a good performance of the method, with up to 26% of gains in the recovery factor regarding the primary recovery, since the application of water injection and gas, individually, was not able to overcome 10 % of gain. The most influential parameter found in the results was the cycle time, with higher recovery factor values obtained with the use of shorter times.

Estudo de tensoativos na organofilização de argila bentonítica para uso em fluido de perfuração à base de óleo

Due to the great challenges encountered in drilling wells, there is a need to develop fluids with appropriated properties and able to meet all the requirements of drilling operations. The physicochemical and rheological properties must be carefully controlled so that a fluid can exercise all its functions. In perforations sensitive to contact with water and "offshore", it becomes necessary the use of oil based drilling fluids, but the bentonite clay cannot be used without a previous surface modification so that their surfaces become hydrophobic. Lately, the oil companies in Brazil use imported organoclays in the preparation of oil-based drilling fluids. The study aimed to modify a calcium clay to increase the affinity of the same organic phase of oil-based drilling fluids, applying three surfactants (OCS, CTAB and UTM 150) at different concentrations. The results indicated that the surfactants UTM 150 and CTAB showed better results compared to OCS. Considering the type of surfactant and concentration as variables used in the statistical analysis, the results indicated that only the surface tension and concentration of calcium oxide in response to organophilization process showed statistically significant effects. The organophilizated clay has potential for application in oil-based drilling fluids.

Aquisição e construção de modelos estáticos análogos a reservatórios petrolíferos com tecnologia lidar e georadar

The present work develops a methodology to establish a 3D digital static models petroleum reservoir analogue using LIDAR and GEORADAR technologies. Therefore, this work introduce The methodolgy as a new paradigm in the outcrop study, to purpose a consistent way to integrate plani-altimetric data, geophysics data, and remote sensing products, allowing 2D interpretation validation in contrast with 3D, complexes depositional geometry visualization, including in environmental immersive virtual reality. For that reason, it exposes the relevant questions of the theory of two technologies, and developed a case study using TerraSIRch SIR System-3000 made for Geophysical Survey Systems, and HDS3000 Leica Geosystems, using the two technologies, integrating them GOCAD software. The studied outcrop is plain to the view, and it s located at southeast Bacia do Parnaíba, in the Parque Nacional da Serra das Confusões. The methodology embraces every steps of the building process shows a 3D digital static models petroleum reservoir analogue, provide depositional geometry data, in several scales for Simulation petroleum reservoir

Influência das tensões tectônicas na permeabilidade da formação Açu - Bacia Potiguar

The behavior of the fluid flux in oil fields is influenced by different factors and it has a big impact on the recovery of hydrocarbons. There is a need of evaluating and adapting the actual technology to the worldwide reservoirs reality, not only on the exploration (reservoir discovers) but also on the development of those that were already discovered, however not yet produced. The in situ combustion (ISC) is a suitable technique for these recovery of hydrocarbons, although it remains complex to be implemented. The main objective of this research was to study the application of the ISC as an advanced oil recovery technique through a parametric analysis of the process using vertical wells within a semi synthetic reservoir that had the characteristics from the brazilian northwest, in order to determine which of those parameters could influence the process, verifying the technical and economical viability of the method on the oil industry. For that analysis, a commercial reservoir simulation program for thermal processes was used, called steam thermal and advanced processes reservoir simulator (STARS) from the computer modeling group (CMG). This study aims, through the numerical analysis, find results that help improve mainly the interpretation and comprehension of the main problems related to the ISC method, which are not yet dominated. From the results obtained, it was proved that the mediation promoted by the thermal process ISC over the oil recovery is very important, with rates and cumulated production positively influenced by the method application. It was seen that the application of the method improves the oil mobility as a function of the heating when the combustion front forms inside the reservoir. Among all the analyzed parameters, the activation energy presented the bigger influence, it means, the lower the activation energy the bigger the fraction of recovered oil, as a function of the chemical reactions speed rise. It was also verified that the higher the enthalpy of the reaction, the bigger the fraction of recovered oil, due to a bigger amount of released energy inside the system, helping the ISC. The reservoir parameters: porosity and permeability showed to have lower influence on the ISC. Among the operational parameters that were analyzed, the injection rate was the one that showed a stronger influence on the ISC method, because, the higher the value of the injection rate, the higher was the result obtained, mainly due to maintaining the combustion front. In connection with the oxygen concentration, an increase of the percentage of this parameter translates into a higher fraction of recovered oil, because the quantity of fuel, helping the advance and the maintenance of the combustion front for a longer period of time. About the economic analysis, the ISC method showed to be economically feasible when evaluated through the net present value (NPV), considering the injection rates: the higher the injection rate, the higher the financial incomes of the final project

Estudo paramétrico da segregação gravitacional na injeção contínua de vapor

Steam injection is the most used method of additional recovery for the extraction of heavy oil. In this type procedure is common to happen gravitational segregation and this phenomenon can affect the production of oil and therefore, it shoulds be considered in the projects of continuous steam injection. For many years, the gravitational segregation was not adequately considered in the calculation procedures in Reservoir Engineering. The effect of the gravity causes the segregation of fluids inside the porous media according to their densities. The results of simulation arising from reservoirs could provide the ability to deal with the gravity, and it became apparent that the effects of the gravity could significantly affect the performance of the reservoir. It know that the gravitational segregation can happen in almost every case where there is injection of light fluid, specially the steam, and occurs with greater intensity for viscous oil reservoirs. This work discusses the influence of some parameters of the rock-reservoir in segregation as viscosity, permeability, thickness, cover gas, porosity. From a model that shows the phenomenon with greater intensity, optimized some operational parameters as the rate flow rate steam, distance between the wells injector-producer, and interval of completion which contributed to the reduction in gravity override, thus increasing the oil recovery. It was shown a greater technical-economic viability for the model of distance between the wells 100 m. The analysis was performed using the simulator of CMG (Computer Modeling Group-Stars 2007.11, in which was observed by iterating between studied variables in heavy oil reservoirs with similar characteristics to Brazilian Northeast

Injeção de vapor e solvente como um método de recuperação avançada em reservatório avançada em reservatórios de óleo pesado

Currently a resource more and more used by the petroleum industry to increase the efficiency of steam flood mechanism is the addition of solvents. The process can be understood as a combination of a thermal method (steam injection) with a miscible method (solvent injection), promoting, thus, the reduction of interfacial tensions and oil viscosity. The use of solvent alone tends to be limited because of its high cost. When co-injected with steam, the vaporized solvent condenses in the cooler regions of the reservoir and mixes with the oil, creating a zone of low viscosity between the steam and the heavy oil. The mobility of the displaced fluid is then improved, resulting in an increase of oil recovery. To better understand this improved oil recovery method, a numerical study of the process was done contemplating the effects of some operational parameters (distance between wells, injection steam rate, kind of solvent and injected solvent volume)on the accumulated production of oil, recovery factor and oil-steam rate. Semisynthetic models were used in this study but reservoir data can be extrapolated for practical applications situations on Potiguar Basin. Simulations were performed in STARS (CMG, 2007.11). It was found that injected solvent volumes increased oil recovery and oil rates. Further the majority of the injected solvent was produced and can be recycled