Banca de DEFESA: LEONARDO BARROS DANTAS BRANDÃO
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.STUDENT : LEONARDO BARROS DANTAS BRANDÃO
DATE: 20/08/2021
TIME: 13:30
LOCAL: Auditório Pós-Graduação Engenharia Civil - CTG - UFPE
TITLE:
NUMERICAL ANALYSIS OF THE DISSOLUTION BY THE FLUID FLOW IN ROCKS AT THE PLUG SCALE WITH INFLUENCE OF VUGS AND FRACTURE
KEY WORDS:
Reactive transport, mineral dissolution, vuggy, fracture, finite element method.
PAGES: 110
BIG AREA: Engenharias
AREA: Engenharia Civil
SUMMARY:
Rock-fluid interactions can cause mineral dissolution, creating flow paths or widen the existing ones, increasing fluid flow. Carbonate rocks have complex physical and geological characteristics. The presence of fractures changes the fluid flow into the rock, which may contribute to the mineral dissolution. Evaporites can be composed by gypsum (CaSO4.H2O), which reacts quickly in contact with water due to its low solubility. Calcite and gypsum dissolutions can create zones that vary from small vuggy to large caves – that is the karstification process. The rock strength can be affected by the roughness of its fracture walls, which impact the fluid and solute circulation, creating tortuous paths. Dissolutions of fracture walls modify their apertures and change permeabilities. To better understand the formation of dissolution zones in rocks and the influence of fractures and vugs, this work numerically simulates the dissolution of gypsum by rock-fluid interaction, using a reactive transport formulation for two-dimensional synthetic scenarios, considering two distinct analyses, in finite elements and at the plug scale: (1) rocks with vugs, in which four plugs with vugs were analyzed, two of them had a random distribution of vugs and two were homogeneous, one of each having a central fracture; (2) rocks with different roughness of the fracture walls, in which four plugs were analyzed (L, R1, R2 and R3). The results of analysis 1 showed a significant increase in dissolution with the fracture and a tendency for the fluid to follow connection paths between the vugs. As a result, some zones farther away from the fluid injection site were dissolved faster than others that were closer. The fracture provides an intense fluid flow in this direction and an expressive advance of dissolution front. In analysis 2, it was observed, in all cases, initially the convergence of the fluid flow to the top of the fracture. At fractured rocks with "corners" (R1, R2 and R3), dissolved zones appeared in the proximity of the corners, while in the L simulation (without corners), dissolution was faster at points closer to the fracture and to the injection site of the fluid. The conclusion is that the presence of fractures tends to direct the flow inside the rock and to accelerate the dissolution process. Roughness creates specific zones of mineral dissolution. The results lead to an understanding of the impact of fractures and vugs on the dissolution in a medium with heterogeneities determined by macropores.
BANKING MEMBERS:
Interna - 1066974 - ANALICE FRANCA LIMA AMORIM
Presidente - 2749584 - IGOR FERNANDES GOMES
Externo à Instituição - MANOEL PORFIRIO CORDAO NETO - UnB