Histerese da permeabilidade relativa ao gás em rochas carbonáticas

Abstract

In the WAG recovery method, alternating the injected fluids promotes changes in the saturation of the porous media. Associated with these changes, two phenomena occur, which are very relevant to the movement of fluids in the rock: (1) capillary trapping of CO 2 during an imbibition process, and (2) hysteresis in the relative permeability curves. Information regarding CO 2 trapping and cyclic hysteresis effects is key for predicting the behavior of the carbonate reservoirs subjected to water alternating gas (CO 2 -WAG) and CO 2 storage processes.The objectives of this study were divided in two parts. First was to investigate, at laboratory scale, the dependence of trapped (residual) gas saturation and gas relative permeability hysteresis on several fluid/rock properties in two-phase flow. The second was to investigate, also at laboratory scale, the hysteresis effects on the gas and water relative permeabilities in three-phase flow. To this end, tests were conducted on carbonate samples that were considered to be heterogeneous. The samples used were coquinas from outcrops that are analogous to pre-salt samples, coming from the Morro do Chaves formation, in the Sergipe-Alagoas Basin, Brazil. The mineralogical composition, pore geometry and petrophysical properties of samples similar to those used in this study were characterized by thin sections and X-ray Computed Tomography.In this study, an experimental methodology was developed to characterize carbonate rocks in such a way as to allow adequate investigation of the WAG method at laboratory scale.Monitoring of the saturation distributions during the displacement tests was conducted through X-ray Computed Tomography (CT), along with detailed procedures for obtaining material balances. The methodology is presented in two steps that include, first, the assembly of an apparatus (A) for studying in-situ capillary trapping of CO 2 in a long sample (A) (76 cm) and, second, the assembly of another apparatus (B) to conduct the three-phase hysteresis test on a short sample (B) (21 cm). The samples were prepared, and the tests followed the procedures considered to be standard for the proposed studies. To investigate the trapping of the non-wetting phase (gas) in two-phase flow (gas-water), drainage and imbibition displacements were carried out under different levels of pressure (700 to 7000 psi) and temperature (22°C and 65°C) in order xvi to evaluate the influence of the rock/fluid properties on the residual saturation of the non-wetting phase (gas) in the porous media. To investigate the hysteresis of water and gas relative permeabilities in three-phase flow, sequences of multiphase drainage and imbibition displacements were carried out in porous media saturated with oil and irreducible water.The results of the investigation on the amount of the non-wetting phase trapped saturation show that the combined effects of increased viscosity and density of the gas in high pressure and temperature conditions increase the maximum gas trapped saturation. The Land trapping coefficient...

Estudo da permeabilidade relativa do sistema água-CO2 em condições de reservatório para carbonatos

“…CT m e CT nm são os números de CT puros de cada fluido obtidos através de tomografias. No mesmo trabalho, Laboissière (2014), considerando as atenuações da rocha saturada com cada fluido e sabendo que S m + S nm = 1, determinou a saturação dos fluidos em um sistema bifásico gáságua, utilizando um nível de energia de 130 KeV com a seguinte equação:…”

“…Por outro lado, foi confirmado que existiu um controle sobre os efeitos de dissolução e precipitação na amostra carbonática mediante a utilização da água do mar carbonatada equilibrada com a composição mineralógica do composite core. As mudanças de porosidade e permeabilidade neste trabalho, não foram alterações severas como as apresentadas em outros estudos que utilizaram água do mar carbonatada não equilibrada e coquinas de afloramento (Yasuda et al 2018;Laboissière, 2014), onde a formação de um canal altamente condutivo aumentaram significativamente a porosidade e permeabilidade das amostras no curso dos experimentos.…”

“…Laboissière (2014), em um trabalho experimental, investigou a influência de diferentes propriedades rocha/fluido sobre a saturação de gás trapeada e a histerese da permeabilidade relativa ao gás em escoamento bifásico de água deionizada de alta salinidade (200000 ppm NaI) e dióxido de carbono. Além disso, investigou os efeitos da histerese de permeabilidades relativas ao gás e à água em escoamento trifásico simulando um processo de recuperação WAG, utilizando água destilada deionizada de alta salinidade (100000 ppm NaI e 100000 ppm NaCl), nitrogênio e óleo mineral EMCA, em duas amostras de coquina (amostra A para os experimentos bifásicos: 76 cm de comprimento e 5,1 cm de diâmetro; amostra B para os experimentos trifásicos: 21 cm de comprimento e 3,5 cm de diâmetro).…”