Electromagnetic (EM) waves are used in the oil and gas industry to identify the geology of the formation and the type of the fluid saturating the medium. There is also an interest to use the electromagnetic waves as an enhanced oil recovery (EOR) method. However, interpretation of logging data generated through electromagnetic waves or determination of the electromagnetic wave propagation in a medium as an EOR method are not easy tasks. This study aims to identify the role of different geological settings with different types of fluid saturations in the response of electromagnetic wave propagation and absorption. To reach this objective multitude-systematic laboratory scale experiments were conducted on different reservoirs fluid and rock pairs. As reservoir mineralogy, different grain size of quartz, clay, or limestone is used to prepare the reservoir rocks at different porosity. Water is known as a good absorber for EM waves, thus, pore space were saturated at different water saturations and a bitumen sample (10,000 cP, 12° API) from Canada. Prepared samples were packed into in-house-built-Plexiglas core holder which allows measurements with EM waves. The response of EM waves propagation and absorption was measured by using a vector network analyzer at varying frequencies (500 MHz to 4 GHz) through dielectric properties (dielectric constant, loss tangent, and penetration depth). The results were used to obtain correlations between dielectric properties and physical properties (reservoir rock mineralogy, porosity, water saturation, and oil saturation) of the reservoir rock-fluid blends. Water saturation gives a perfect correlation with dielectric constant and loss tangent values of the saturated medium. Because dielectric constant and loss tangent parameters provide an idea on the absorption characteristics of EM wave in the medium, and because water is a strong EM wave absorber, as it was expected, with the increase in water saturation, the dielectric constant and loss tangent parameters of the medium are also increased; on the other hand, penetration depth was decreased. With the increase in quartz content in the medium, it has been observed that EM wave penetration is enhanced. As a result, several correlations were created in this study and they can be used to better interpret the reservoir mineralogy and fluid saturation as a response to EM wave logging. Moreover, these results can be used to estimate the effective area (penetration depth) of EM wave as an EOR method in different mediums.

Heterogeneity to some extent is realized in every reservoir. Variable properties, namely fluid saturations and lithology, make it very difficult to accurately estimate the bulk dielectric response of the reservoir. This study isolates and identifies the dependencies of the bulk dielectric response to changing water content, quartz content, limestone content, oil content, and clay content. A multitude of experiments were run where the identified parameters were systematically isolated and varied to capture both the contribution from the rock matrix and the pore space. Reservoir rock was simulated by mixing the rock matrix components with the fluids to form unconsolidated core samples. The bulk dielectric properties, both the real and imaginary components, were measured for each of the seventy five different samples using a vector network analyzer (VNA) in conjunction with a dielectric probe. Individual experiments were analyzed comparatively and the dielectric responses are presented as a function of each isolated parameter. Understanding the general dependencies and sensitivity of the dielectric behavior of the reservoir is vital for various aspects of petroleum including electromagnetic heating and well logging. The complex and dynamic downhole environment creates coupled and mutual interactions making estimation of the bulk response very difficult. Isolation of each variable allows for the identification of the governing relationship of each parameter with the dielectric response. In this study, linearity is established for the dielectric response of all investigated parameters. The sensitivity of the complex permittivity is represented as the magnitude of change as a function of variable fluid saturation or lithology. This enables the drivers of dielectric heating to be quantified, namely the increase in complex permittivity with increasing water saturation. The established relationships allow for the estimation of the dielectric response of the reservoir as a result of heterogeneity present. Variable properties that change with position and time are accounted for by understanding the corresponding change in the complex permittivity of the reservoir. By illuminating the complex permittivity relationship as a function of rock minerology and fluid saturations, a more holistic understanding of absorption mechanics can be achieved. The study offers the unique ability to express the intrinsic relationship experienced under the influence of reservoir properties. The presented relationships also enable the estimation of dielectric properties as a function of reservoir heterogeneity.

This study reviews the existing oil and gas fields in Brazil located both onshore and offshore. Focus is on geology and production history of Santos, Campos, Reconcavo, Sergipe, and Potiguar Basins. We mainly reviewed the geological and reservoir characteristics of these basins, their production history, applied enhanced oil recovery (EOR) methods, and we finally made some EOR recommendations which may help to increase hydrocarbon recoveries in each basin. At the beginning of the current decade, Brazil was producing almost 2 MM barrels of oil per day. Nowadays, the pre-salt fields alone (that started operating 15 years ago) produce an average of 1.67 MM bbl/d with a 2.73 MM bbl/d total daily oil production. In other words, the oil production from the basins other than the pre-salt fields started to decline of more than 50% in their production levels. The divestment of many assets, located both onshore and offshore, opens a window of opportunity and a need for the new owners to apply EOR methods to bring back production to higher levels and recover their investments. By reviewing the data from three onshore fields from Reconcavo, Sergipe, and Potiguar and two offshore fields from the Campos basin, this paper has discussed issues and assessed alternatives that may similarly be applicable to other fields in the same basins. Buracica, Carmopolis, and Canto do Amaro fields presented almost none to low increase in production. One of the reasons may be credited to paraffin wax deposition. To avoid wax deposition and increase oil production, we proposed to combine two methods; a thermochemical method to avoid the buildup of wax with the addition of surfactant to the injected fluid to reduce the interfacial tension between water and oil and increase recovery. Both Jubarte and Marlim have achieved success with waterflooding but currently, a continuous decline is observed. Polymer flooding is proposed as a solution in these cases. The pre-salt fields are still ramping up production at very high rates. Hence, as an alternative, in those reservoirs, CO2-WAG might be applied in the near future before reaching a decline in the oil production. This study briefly discusses the status of the oil and gas fields in Brazil both located onshore and offshore. Moreover, it provides quick recommendations for the existing problems in Brazil during oil and gas production via EOR methods.