Polymer Injection Projects in Brazil: Dimensioning, Field Application and Evaluation

Abstract

Polymer injection in petroleum reservoirs aiming at the enhancement of oilrecovery has been used worldwide for decades. Polymers act basically increasingthe injected water viscosity and reducing the porous media permeability, thenimproving the vertical and areal sweep efficiency. Pilot polymer injection projects for mobility correction are currentlyunderway in three Brazilian fields operated by Petrobras, namely Carmópolis(Sergipe state), Buracica (Bahia state) and Canto do Amaro (Rio Grande do Nortestate), the first and the second in full operation and the third in its initialstage. With these projects, Petrobras has acquired know-how actuating in allprocess steps such as the laboratory tests, the dimensioning and programming ofthe field operation, the field implementation and finally the analysis andinterpretation of the results. The present article describes Petrobras experience during the several phasesof field projects implementation. The laboratory data for relevant parametersare presented and discussed. These data were essential to the polymer floodingprojects design and serve as input data for simulation with IMEX™, which willbe useful for the economical and technical evaluation of these projects. Introduction The purpose of polymer injection is to reduce water-oil mobility ratio. Themechanism of this process is to increase the viscosity of the water phase. Witha reduced mobility ratio, the sweep efficiency is increased and, as aconsequence, the oil recovery is enhanced [1,2]. Depending on the polymer thisincrease in the viscosity can cause also a reduction in the water effectivepermeability in the swept zone [2]. This reduction acts favorably as asecondary effect, restoring part of the reservoir pressure after the polymerpassage (residual resistance factor). This fact may cause a correction of theinjection profile of the wells by means of the rearrangement of the residentfluids. Instead of lowering the residual oil saturation, as usual in othermethods, polymer injection improves oil recovery beyond water flooding byincreasing the contacted volume of the reservoir (sweep efficiency). Thisprocess has its greatest potential in reservoirs that are moderatelyheterogeneous, contain viscous oil, and have adverse water-oil mobility ratio[1–4]. Polymer flooding is the best established of the chemical enhanced oilrecovery methods. Laboratory and field application have shown that the polymerflooding process is most effectively applied in the early stage of a waterflooding project when the mobile oil saturation is still high. However, it hasbeen applied with positive results to reservoirs in a rather mature stage ofwaterflooding like the three reservoirs studied here. The present paper shows in a chronological order the steps followed byPetrobras for the implementation of three polymer projects for mobilitycontrol:Reservoir/pilot area selectionWater injection analysisPolymer selection (laboratory tests)Design of the polymer slugImplementation and evaluation On the correct choice of the reservoir, followed by the specification anddesign of the polymer bank to be injected, depend the technical and economicalsuccess of the process [5–10]. The reservoirs were chosen based on literature parameters [8–10]. Theselection of the most suitable polymer for a specific reservoir, defined inlaboratory tests, is a critical point and involves the intrinsic properties ofthe product along with the porous media characteristics (polymerretention/adsorption, residual resistance factor, inaccessible pore volume, shear degradation, etc.).

Development of Isotherm Polymer/Surfactant Adsorption Models in Chemical Flooding

“…The static method is easy and inexpensive. However, the results may not represent the field values because the exposed surface of unconsolidated rock is not the same as the one of a reservoir; the mechanical entrapment component of polymer is not measured and the wettability of the disaggregated rock may be different from that of the reservoir rock (Melo et al, 2002). The second method is measurement of adsorption in the dynamic flow condition by core flooding.…”

The role of matching relationship between polymer injection parameters and reservoirs in enhanced oil recovery

“…Melo et al (2001) studied polymer injection projects in Brazil and they expressed that polymer flooding is the best established method of the chemical EOR. Laboratory and field applications have shown that the polymer flooding process is more effectively applied at the early stage of a water flooding project when the mobile oil saturation is still high (Melo et al, 2002). Besides, the research on physical and numerical simulation by specialists and scholars also indicated that the earlier the polymer is injected, the higher the oil recovery factor is enhanced, and the polymer injection profile can be improved effectively when the profile controlling methods are used before or at the initial stage of polymer injection, which makes the effect of polymer flooding better (Feng et al, 2012).…”

Optimization of a Large Polymer Flood With Full-Field Streamline Simulation

“…Pattern Optimization by Changing Polymer Throughput Feng et al (2009) showed that good reservoir characterization and dynamic adjustment of injection and production rates contribute significantly to achieve better waterflood performance. The same philosophy becomes more critical for a polymer-flood project because a polymer-flood project is strongly operational-expenditure driven because of the high chemical cost.…”