Simulação numérica do escoamento de fluido de lei de potência com partículas para o preenchimento de fraturas

Abstract

The invasion of drilling fluid from the annular region into the formation during the drilling an oil well is known as lost circulation. Besides the cost related to fluid replacement, there is a possibility of damaging the formation. A potential solution to the lost circulation is adding solid particles to the drilling fluid. The solids, known as Lost Circulation Materials (LCM), seals fractures and highly permeable formations. Usually, drilling fluid has non Newtonian characteristics, só a power law fluid is used. In this work, the use of non-Newtonian fluids with solid particles to obturate fractured formations is numerically studied. The annular region of the well with a discrete and transverse fracture is idealized as a vertical channel of rectangular cross section in contact with a horizontal channel, which represent the fracture. The numerical simulation is performed via the DDPM, which solves the fluid flow equations and the particle-fluid interactions, coupled to the DEM, which solves the contacts among particles and between particles and walls. The characterization of the fracture filling process is obtained by varying the parameters: Reynolds number in the vertical channel ReCH,i=(50; 125; 250; 500; 1250), fluid loss ratio in the fracture qf=(5; 10; 20%), particle specific mass ρp=(1600, 2500 Kg/m3), and the rheological characteristics of the fluid, considering power law fluid with apparent viscosity μβ =(0,00855; 0,0163; 0,0377 Pa.s) at 1000s-1. The results are evaluated as a function of response variables such as the percentual fluid loss ratio in the fracture (qf), the volumetric fluid loss on the fracture (Qβ,FR,O), the dimensionless pressure on the vertical channel entrance (PCH,i), the dimensionless pressure on the vertical channel, and dimensional properties of the particle bed formed on the fracture (e.g. height, length). The increase of Reynolds number in the channel intensifies the invasion phenomenon, since Qβ,FR,O increases. The use of non Newtonian fluid is capable to reduce the effect of the loss circulation, as the increase in apparent viscosity μβ reduces the leakage volumetric flow. The use of solid particles combat the loss circulation due to the formation of a particle bed in the fracture and the particle specific mass presents a great influence in the particle bed.