A model for predicting temperature and pressure profiles in gas-lifted oil wells

Resumo

This work presents a methodology for predicting temperature and pressure profiles in oil wells that employ the artificial lift technique through gas-lift. When the reservoir pressure is not sufficient to bring the oil to the surface or when increasing production efficiency is desired, artificial lift techniques are employed. The injection of gas (gas-lift) is one of the most commonly used techniques. In the oil and gas industry, the accurate prediction of temperature profiles during various operations is crucial for ensuring well integrity. These profiles serve as inputs for calculating variations in annular pressures, casing stress, corrosion rates, and other critical parameters. However, calculating these profiles is challenging, requiring data on the well's underground structure, simultaneous resolution of the differential equations governing heat transfer phenomena in the structure, and modeling the hydrodynamic behavior of fluids. In wells where production operations are carried out using gas-lift, the complexity is even greater because the annular fluid, previously static, now circulates downward. This fact increases the number of equations to be solved and the number of fluids to be modeled. Thus, the development of strategies for obtaining these profiles is justified. To achieve the proposed objective, the methodology adopted in this work is based on three main steps: a) description of the mathematical formulation of the problem, considering the energy, momentum, and mass balance in the flow of both the produced fluid and the injected fluid; b) development of a numerical strategy enabling the simultaneous solution of the equations formulated in the previous step, thus allowing the determination of temperature and pressure profiles in the well; and c) verification of the strategy by comparing the results obtained using the procedure described in this work with thermal profiles from wells reported in the literature. The main contribution of this work is to enable the prediction of thermal profiles in oil wells in production operations with artificial lift by gas injection, allowing these profiles to be used in the design and monitoring of wells, thereby adding safety and efficiency to the operation.