Abstract Water injection is often used as a recovery method for light oil reservoirs; however, for heavy oil reservoirs its efficiency is not so high mainly due to the unfavorable water-oil mobility ratio. For this reason, well placement is an important step of the production strategy definition because it can guarantee the economic viability of heavy-oil, deep water fields.
This work aimed to analyze the behavior of heavy oil displacement by water injection, through both experimental and numerical simulation studies. A rectangular plate filled with porous media was used; its petrophysical characteristics were determined, as well as the relative permeability and capillary pressure. Two horizontal wells were used and the laboratory test was performed in two stages: first, an oil saturation phase and then a displacement phase. Water saturation maps were generated for the two stages, in order to better analyze distortions due to friction effects in the horizontal wells.
A numerical simulation model was built to reproduce the behavior observed in the experiment and compare the friction pressure drop effects. It was further used as the basis of a hypothetical reservoir prototype, in field scale; the results from the simulations reproduced the experiment data qualitatively, however, some differences were observed. The friction pressure drop in the wellbore did not seem to affect the flow, especially according to the simulation results.
Introduction With more frequent use of horizontal wells and new offshore oil discoveries of viscous oil, it is important to correctly describe the behaviour of viscous oil displacement in porous media[1].
This work aimed to study such behavior through a methodology that involved an experimental displacement test by injecting water in viscous oil through horizontal wells, and the characterization of a porous media.
The fluids and porous media characterization[2] are presented in a correlated work[3]. Since this work involves very unfavourable mobility ratio, the initial discussion will focus on the conditions for displacement stability taking into consideration the high oil viscosity.
Scale transformation from a model to a prototype was studied and the results for the prototype were calculated by scale transformation and by numerical simulation. The pressure, production and saturation distributions were simulated for the model and compared to the laboratory measurements.
Porous Media. The porous media is an Eolian sandstone from Botucatu formation[4,5] obtained from an outcrop in Ribeirão Claro, PR, Brazil. It was preliminarily cut in a parallelepiped form (88cm × 33cm × 3.2cm), with 24% porosity and 587 mD absolute permeability[6]. The capillary pressure and the water oil stable relative permeabilities[7] can be seen in Table 1, where the normalised water saturation presented is defined by Eq. (1):
(1)
Oil Displacement Test Experimental and Simulation Model Results. The plate was saturated with water under vacuum. The initial water saturation was obtained by injecting the 212 cP viscous oil laterally in linear displacement geometry; the oil injection rate was 0.15 cm3/min. Figure 1 shows a picture[3] of the encapsulated rock plate used in the experiments and the laboratory apparatus. The operating pressure had to be kept to low values due to the large superficial area of the model, otherwise the plate containing the porous media could be damaged. This phase of the experiment provided the irreducible water saturation (Swi) for Eq. (1).