Uso do método de Monte Carlo para estimativa do índice de injetividade e do nível de poços em reservatórios depletados

Abstract

Drilling, completion, and workover operations require a proper planning to maintain well control. The main idea is to fill the well with a killing fluid that creates a hydraulic barrier by developing a higher hydrostatic pressure than the formation pore pressure. Moreover, this barrier should be capable of preventing the fluids migration from the rock reservoir into the well. Frequently, well interventions in depleted reservoirs take place with the fluid level below the surface in order to prevent the excessive fluid loss to formation, due to the overbalance from hydrostatic pressure. However, this level fluid decreases over time according to the well injectivity. Therefore, to maintain the hydraulic barrier, the well should be periodically refilled. Due to the level of the completion fluid sits bellow surface, the well is refilled based on intuitive knowledge or fluid level monitoring by an acoustic measurement system. This work considers a fluid rock system dataset to analyze the probability distribution of the injectivity index and the overbalance of a well when it is refilled at a specific flow rate. In the methodology, the Monte Carlo method was applied on the transient solution for the model of complete displacement of the injection fluid using the ModelRisk software. The results from Monte Carlo simulation presents good insight for the well injectivity, overbalance and fluid level over time considering the uncertainties in reservoir and fluid input parameters. The results from this work indicate that fluid viscosity and effective permeability of the oil are the properties whose uncertainties in the measurement cause greater impact when calculating well injectivity and overbalance.