Influência do tempo de adição do policarboxilato em pastas de cimento Portland para cimentação de poços petrolíferos

Cement pastes used in cementing oil wells operations are prepared according to the specific characteristics of each well. The physical properties requested for each folder formulation depend on the temperature and pressure of the well to be cemented. The rheological properties of the pulp are important control parameter for efficiency in transportation and positioning the folder during the cementing operation. One of the main types of additive used for the adjustment of rheological properties of cement pastes is the dispersant additive. This work aims to study the influence of variation of the time of addition of the polycarboxylate (0, 5, 10 and 15 minutes) in cement pastes, considering the initial periods of hydration of cement particles as fundamental point for better performance dispersant additive. Pastes were prepared with a density set at 15.6 lb/gal (1.87 g/cm3) and polycarboxylate concentrations ranging from 0.01 gpc to 0.05 gpc circulation temperature (BHCT) of 51°C and static temperature (BHST) of 76 C. The pastes were characterized from a rheological measurements, volume filtered, thickening time and resistance to compression formulations. Also were carried out tests Diffraction X-ray (XRD) and Scanning Electron Microscopy (MEV). The results showed that the addition of policaboxilato after 15 minutes decreased by 70% the values of rheological parameters. According to results of DRX and MEV, the addition of dispersant after 15 minutes did not affect the chemical reactions and subsequent formation of cement hydration products. A study of the economic feasibility to realize the financial benefits of the technique, which can be seen only with the use of the technique in this work to reduce the cost of production of cement paste was carried out, can get up to $ 1015.00 for each folder 100 barrels produced with said formulations.

Influência do tempo de adição do policarboxilato em pastas de cimento Portland para cimentação de poços petrolíferos

Cement pastes used in cementing oil wells operations are prepared according to the specific characteristics of each well. The physical properties requested for each folder formulation depend on the temperature and pressure of the well to be cemented. The rheological properties of the pulp are important control parameter for efficiency in transportation and positioning the folder during the cementing operation. One of the main types of additive used for the adjustment of rheological properties of cement pastes is the dispersant additive. This work aims to study the influence of variation of the time of addition of the polycarboxylate (0, 5, 10 and 15 minutes) in cement pastes, considering the initial periods of hydration of cement particles as fundamental point for better performance dispersant additive. Pastes were prepared with a density set at 15.6 lb/gal (1.87 g/cm3) and polycarboxylate concentrations ranging from 0.01 gpc to 0.05 gpc circulation temperature (BHCT) of 51°C and static temperature (BHST) of 76 C. The pastes were characterized from a rheological measurements, volume filtered, thickening time and resistance to compression formulations. Also were carried out tests Diffraction X-ray (XRD) and Scanning Electron Microscopy (MEV). The results showed that the addition of policaboxilato after 15 minutes decreased by 70% the values of rheological parameters. According to results of DRX and MEV, the addition of dispersant after 15 minutes did not affect the chemical reactions and subsequent formation of cement hydration products. A study of the economic feasibility to realize the financial benefits of the technique, which can be seen only with the use of the technique in this work to reduce the cost of production of cement paste was carried out, can get up to $ 1015.00 for each folder 100 barrels produced with said formulations.

Análise de sedimentos associados à atividade de perfuração na plataforma continental externa, Bacia Potiguar - Brasil

This study was developed in an area located on the outer shelf in the Potiguar Basin, Brazilian equatorial margin; this tropical shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system. Field sampling was carried out during 3 cruises surrounding a shallow-water exploratory well to compare sediment properties of the seafloor, including grainsize, texture, mineral composition, carbonate content, and organic matter. Cruise 1 (C1) was carried prior to drilling, while Cruise 2(C2) and 3 (C3) respectivelly 3 and 12 months after drilling. The sample grid used had 16 stations located along 4 radials from 50 m the well up to a distance of 500 m. Sediments were analyzed in the first 0-2 cm, and 0-10 cm layers. The results show that sedimentary cover around the well is poor to very poorly sorted, with the particle size predominantly in the medium to coarse sand fraction, followed by gravel and mud. The content of calcium carbonate is greater than 96%, associated to bioclastic sediments, and the content of organic matter is less than 12%. Only minor sedimentological variations occured in the area affected by drilling operations. Mainly observed during the second cruise, in terms of a change in grain size distribution associated to an increase in siliciclastic content, This impact occurred in the most surficial sediment (0-2 cm), in the radial closest to the well (50 m), and could suggest the effects of drilling. However, in the third cruise, one year after drilling, the sediments return to show the same characteristics as in the first cruise. These results show no significant sedimentological variations due to drilling activity, and indicate that ocean dynamics in this area was high enough to recover the environment original characteristics.

Análise de sedimentos associados à atividade de perfuração na plataforma continental externa, Bacia Potiguar - Brasil

This study was developed in an area located on the outer shelf in the Potiguar Basin, Brazilian equatorial margin; this tropical shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system. Field sampling was carried out during 3 cruises surrounding a shallow-water exploratory well to compare sediment properties of the seafloor, including grainsize, texture, mineral composition, carbonate content, and organic matter. Cruise 1 (C1) was carried prior to drilling, while Cruise 2(C2) and 3 (C3) respectivelly 3 and 12 months after drilling. The sample grid used had 16 stations located along 4 radials from 50 m the well up to a distance of 500 m. Sediments were analyzed in the first 0-2 cm, and 0-10 cm layers. The results show that sedimentary cover around the well is poor to very poorly sorted, with the particle size predominantly in the medium to coarse sand fraction, followed by gravel and mud. The content of calcium carbonate is greater than 96%, associated to bioclastic sediments, and the content of organic matter is less than 12%. Only minor sedimentological variations occured in the area affected by drilling operations. Mainly observed during the second cruise, in terms of a change in grain size distribution associated to an increase in siliciclastic content, This impact occurred in the most surficial sediment (0-2 cm), in the radial closest to the well (50 m), and could suggest the effects of drilling. However, in the third cruise, one year after drilling, the sediments return to show the same characteristics as in the first cruise. These results show no significant sedimentological variations due to drilling activity, and indicate that ocean dynamics in this area was high enough to recover the environment original characteristics.

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.

Modelagem dinâmica e simulação computacional de poços de petróleo verticais e direcionais com elevação por bombeio mecânico

LINS, Filipe C. A. et al. Modelagem dinâmica e simulação computacional de poços de petróleo verticais e direcionais com elevação por bombeio mecânico. In: CONGRESSO BRASILEIRO DE PESQUISA E DESENVOLVIMENTO EM PETRÓLEO E GÁS, 5. 2009, Fortaleza, CE. Anais... Fortaleza: CBPDPetro, 2009.

Perfuração espontânea de colédoco em adolescente

Spontaneous perforation of the common bile duct is rare. It happens predominantly in children and it is related to obstructive disease of the biliary tract. We present a case of an 18 year-old male patient, with ulcerative rectocolitis associated with malignant tumor of the head of pancreas. The patient developed an acute abdomen syndrome and laparotomy, a spontaneous perforation of common bile duct was evidenced. The authors make a revision of the clinical aspects of that pathology

Adição de superplastificante e anti-segregante à base de CMC em pastas de cimento para Poços de Petróleo

Oil well cementing materials consist of slurries of Special class Portland cement dispersed in water. Admixtures can be used to provide the necessary fluidity, so the material can be efficiently pumped down as well as penetrate porous rocks with controlled filter loss. Construction admixtures can be used to modify the properties of oil well cements provided they can withstand and hold their properties at the higher than ambient temperatures usually encountered in oil fields. In civil construction, superplasticizer play the role of dispersants that reduce the facto r of water cement improve mechanical properties and fluidity of the cement, whereas anti-segregation agents improve the workability of the slurry. In the present study, oil well cement slurries were produced adding both a dispersant and an anti-segregation agent conventionally used in Portland CPII-Z-32 RS cement aiming at materials for primary cementing and squeeze operations. Three basic aspects were evaluated: fluidity, filter loss and the synergetic effect of the admixtures at two temperatures, i.e., 27°C and 56°C, following API RP 10B practical recommendations. The slurries were prepared using admixture concentrations varying from 2.60 Kgf/m3 (0.02 gallft3) to 5.82 Kgf/m3 (0.045 galJft3) BWOC. The density of the slurries was set to 1.89 g/cm3 (15.8 Ib/gal). 0.30 to 0.60% BWOC of a CMC-based anti-segregation agent was added to the cement to control the filter loss. The results showed that the addition of anti-segregation at concentrations above 0.55% by weight of cement resulted in the increased viscosity of the folders in temperatures evaluated. The increasing the temperature of the tests led to a reduction in the performance of anti-segregation. At concentrations of 5.20 kgf/m3 (0,040 gallft3) and 5.82 Kgf/m3 (0,045 gal/ft 3) observed a better performance of the properties evaluated in the proposed system. At low temperature was observed instability in the readings of rheology for all concentrations of anti-segregation. Contents that increasing the concentration of anti¬-segregation is limited concentrations greater than 0.55 % BWOC of the CMC in temperature analyzed. The use of the system with CMC promoted a good performance against the properties evaluated. The principal function of anti¬-segregation was optimized with increasing concentration of superplasticizer, at temperatures above the 2rC. The study of the behaviour of systemic additives, resulting in slurries of cement, which can be optimized face studies of other intrinsic properties in oil fields

Influência da vermiculita expandida na resistência à compressão e reologia de pastas cimentantes de poços de petróleo

Several problems related to the loss of hydraulic seal in oilwells, causing gas migration and/or contamination of the production zone by water, have been reported. The loss of the hydraulic seal is a consequence of cracks which can be occasioned either by the invasion of gas during the wait on cement or by the expansion of the casing causing the fracture of the cement sheath. In case of the pressure of the formation is higher than the pressure in the annulus, gas can migrate into the slurry and form microannulus, which are channels where gas migrates after the cement is set. Cracks can be also occasioned by the fracture of the cement sheath when it does not withstand the thermal and dynamic loads. In reservoirs where the oil is heavy, steam water injection operation is required in order to get the oil flowing. This operation increases the temperature of the casing, and then it expands and causes the fracture of the cement sheath in the annulus. When the failures on the cement are detected, remedial cementing is required, which raise costs caused by the interventions. Once the use of cement in the construction civil sector is older than its use in the petroleum sector, it is common to bring technologies and solutions from the civil construction and apply them on the petroleum area. In this context, vermiculite, a mineral-clay widely encountered in Brazil, has been used, on its exfoliated form, in the civil construction, especially on the manufacture of lights and fireproof concretes with excellent thermal and acoustical properties. It has already been reported in scientific journals, studies of the addition of exfoliated vermiculite in Portland cements revealing good properties related to oilwell cementing operations. Thus, this study aimed to study the rheological behavior, thickening time, stability and compressive strength of the slurries made of Portland cement and exfoliated vermiculite in 5 different compositions, at room temperature and heated. The results showed that the compressive strength decreased with the addition of exfoliated vermiculite, however the values are still allowed for oiwell cementing operations. The thickening time of the slurry with no exfoliated vermiculite was 120 min and the thickening time of the slurry with 12 % of exfoliated vermiculite was 98 min. The stability and the rheological behavior of the slurries revealed that the exfoliated vermiculite absorbed water and therefore increased the viscosity of the slurries, even though increasing the factor cement-water. The stability experiment carried out at 133 ºF showed that, there was neither sedimentation nor reduction of the volume of the cement for the slurry with 12 % of exfoliated vermiculite. Thus, the addition of exfoliated vermiculite accelerates the set time of the cement and gives it a small shrinkage during the wait on cement, which are important to prevent gas migration

Análise do comportamento reológico de pastas de cimento contendo resíduos de pneu para poços de petróleo

The low tenacity presented by the Portland cement pastes used in the oil wells cementation has been motivating several researches with attention focused on alternative materials. Additives have been developed to generate flexible pastes with mechanical resistance capable to support the expansions and retractions of the metallic covering of the wells that submit to the steam injection, technique very used to increase the recovery factor in oil reservoirs with high viscosity. A fresh paste with inadequate rheological behavior may commit the cementation process seriously, involving flaws that affect the performance of the paste substantially in the hardened state. This work proposes the elaboration and the rheological analysis of Portland cement pastes with addition of residues of rubber tire in several proportions, with the aim of minimizing the damages provoked in the hem cementing of these wells. By thermogravimetric analysis, the particles of eraser that go by the sieve of 0,5mm (35 mesh) opening and treated superficially with NaOH solution of 1 mol/L presented appropriate thermal resistance for wells that submit to thermal cyclic. The evaluation of the study based on the results of the rheological analysis of the pastes, complemented by the mechanical analysis, thickening, stability, tenor of free water and filtrate loss, being used as parameter a paste reference, without rubber addition. The results showed satisfactory rheology, passive of few corrections; considerable loss of mechanical resistance (traction and compression), compensated by earnings of tenacity, however with established limits for its application in oil wells; satisfactory stability, free water and thickening time

Adição de vermiculita expandida mícron em pastas de baixa densidade para cimentação de poços de petróleo

The northeastern region of Brazil has a large number of wells producing oil using a method of secondary recovery steam injection, since the oil produced in this region is essentially viscous. This recovery method puts the cement / coating on thermal cycling, due to the difference in coefficient of thermal expansion between cement and metal coating causes the appearance of cracks at this interface, allowing the passage of the annular fluid, which is associated with serious risk socioeconomic and environmental. In view of these cracks, a correction operation is required, resulting in more costs and temporary halt of production of the well. Alternatively, the oil industry has developed technology for adding new materials in cement pastes, oil well, providing high ductility and low density in order to withstand the thermo-mechanical loads generated by the injection of water vapor. In this context, vermiculite, a clay mineral found in abundance in Brazil has been applied in its expanded form in the construction industry for the manufacture of lightweight concrete with excellent insulation and noise due to its high melting point and the presence of air in their layers lamellar. Therefore, the vermiculite is used for the purpose of providing low-density cement paste and withstand high temperatures caused by steam injection. Thus, the present study compared the default folder containing cement and water with the folders with 6%, 8% and 10% vermiculite micron conducting tests of free water, rheology and compressive strength where it obtained the concentration of 8 % with the best results. Subsequently, the selected concentration, was compared with the results recommended by the API standard tests of filtered and stability. And finally, analyzed the results from tests of specific gravity and time of thickening. Before the study we were able to make a folder with a low density that can be used in cementing oil well in order to withstand the thermo-mechanical loads generated by steam injection

Avaliação da influência do nacl em pastas de cimento portland para cimentação de poços de petróleo em zonas evaporíticas

One of the major current challenges for oilwell companies is the extraction of oil from evaporitic zones, also known as pre-salt basins. Deep reservoirs are found under thick salt layers formed from the evaporation of sea water. Salt layers seal the flow of oil from underneath rock formations, which store hydrocarbons and increase the probability of success in oil and gas exploration. Oilwells are cemented using Portland-based slurries to promote mechanical stability and zonal isolation. For pre-salt oilwells, NaCl must be added to saturate the cement slurries, however, the presence of salt in the composition of slurries affects their overall behavior. Therefore, the objective of the present study was to evaluate the effect of the addition of 5 to 25% NaCl on selected properties of Portland-based slurries. A series of tests were carried out to assess the rheological behavior, thickening time, free water and ultrassonic compressive strength. In addition, the slurries were also characterized by thermal analysis, X ray diffraction and scanning electron microscopy. The results showed that the addition of NaCl affected the thickening time of the slurries. NaCl contents up to 10% shortened the thickening time of the slurries. On the other hand, concentrations in excess of 20% not only extended the thickening time, but also reduced the strength of hardened slurries. The addition of NaCl resulted in the formation of a different crystalline phase called Friedel´s salt, where free chlorine is bonded to tricalcium aluminate

Estudos de Durabilidade Frente ao Ataque Ácido de Compósitos Portland-Polímero para Cimentação de Poços de Petróleo

Portland-polymers composites are promising candidates to be used as cementing material in Northeastern oil wells of Brazil containing heavy oils submitted to steam injection. In this way, it is necessary to evaluate its degradation in the commonly acidizind agents. In addition, to identify how aggressive are the different hostile environments it is an important contribution on the decision of the acidic systems to be used in. It was investigated the performance of the Portland-polymer composites using powdered polyurethane, aqueous polyurethane, rubber tire residues and a biopolymer, those were reinforced with polished carbon steel SAE 1045 to make the electrochemical measurements. HCl 15,0 %, HCl 6,0 % + HF 1,5 % (soft mud acid), HCl 12,0 % + HF 3,0 % (regular mud acid) and HAc 10 % + HF 1,5 % were used as degrading environment and electrolytes. The more aggressive acid solution to the plain Portland hardened cement paste was the regular mud acid, that showed loss of weight around 23.0 %, followed by the soft mud acid, the showed 11.0 %, 15.0 % HCl with 7,0 % and, at last the 10.0 % HAc plus HF 1.5 % with just 1.0 %. The powdered polyurethane-composite and the aqueous polyurethane one showed larger durability, with reduction around 87.0 % on the loss of weight in regular mud acid. The acid attack is superficial and it occurs as an action layer, where the degraded layer is responsible for the decrease on the kinetic of the degrading process. This behavior can be seen mainly on the Portland- aqueous polyurethane composite, because the degraded layer is impregnated with chemically modified polymer. The fact of the acid attack does not have influence on the compressive strength or fratography of the samples, in a general way, confirms that theory. The mechanism of the efficiency of the Portland-polymers composites subjected to acid attack is due to decreased porosity and permeability related with the plain Portland paste, minor quantity of Ca+2, element preferentially leached to the acidic solution, wave effect and to substitute part of the degrading bulk for the polymeric one. The electrolyte HAc 10 % + HF 1,5 % was the least aggressive one to the external corrosion of the casing, showing open circuit potentials around +250 mV compared to -130 mV to the simulated pore solution to the first 24 hours immersion. This behavior has been performed for two months at least. Similar corrosion rates were showed between both of the electrolytes, around 0.01 μA.cm-2. Total impedance values, insipient arcs and big polarization resistance capacitive arcs on the Nyquist plots, indicating passivity process, confirm its efficiency. In this way, Portlandpolymers composites are possible solutions to be succeed applied to oilwell cementing concomitant submitted to steam injection and acidizing operation and the HAc 10,0 % + HF 1,5 % is the less aggressive solution to the external corrosion of the casing

Desenvolvimento de pastas de cimento flexíveis para poços de petróleo submetidos à injeção de vapor utilizando látex do tipo SBR

Novel cementing materials formulations containing flexible polymeric admixtures have been studied aiming at improving the mechanical behavior of oil well cement slurries submitted to steam injection. However, research activities in this sector are still under development. The steam injected directly into the well causes casing dilation, which after a reduction in temperature, tends to return to its original dimensions, resulting in crack formation and hydraulic isolation loss of the well, which will result in shortening of well life. In this scenario, the objective of the present study was to evaluate the mechanical behavior of Portland-based slurries containing SBR latex, applied in oil well cementing of wells submitted to steam injection. Were formulated slurries with densities of 1.797 g/cm3 (15.0 lb/Gal) and 1.869 g/cm3 (15.6 lb/Gal), containing admixtures with a latex concentration of 0; 66.88; 133.76; 200.64 and 267.52 L/m3 (0, 0.5, 1.0, 1.5 and 2.0 gpc). Tests including rheology, fluid loss control, thickening time, API compressive strength and splitting tensile strength, beyond steam injection simulation. Microstrutural characteristics of the slurries were also performed (XRD, TG, FTIR and SEM). The results showed that increasing the polymer concentration increased in the rheological properties and fluid loss, and a decrease in the elasticity modulus of the cement slurries. The results obtained showed that the slurries can be applied in cementing operations of oil wells submitted to steam injection.

Caracterização de atapulgita visando aplicação para reforço de materiais poloméricos

The clay mineral attapulgite is a group of hormitas, which has its structures formed by microchannels, which give superior technological properties classified the industrial clays, clays of this group has a very versatile range of applications, ranging from the drilling fluid for wells oil has applications in the pharmaceutical industry. Such properties can be improved by activating acid and / or thermal activation. The attapulgite when activated can improve by up to 5-8 times some of its properties. The clay was characterized by X-ray diffraction, fluorescence, thermogravimetric analysis, differential thermal analysis, scanning electron microscopy and transmission electron microscopy before and after chemical activation. It can be seen through the results the efficiency of chemical treatment, which modified the clay without damaging its structure, as well as production of polymer matrix composites with particles dispersed atapugita