Predicting well inflow performance relationship accurately is very important for production engineers. From these predictions, future plans for handling and improving well performance can be established. One method of predicting well inflow performance is to use artificial neural networks. Vogel's reference curve, which is produced from a series of simulation runs for a reservoir model proposed by Weller, is typically used to predict inflow performance relationship for solution-gas-drive reservoirs. In this study, I reproduced Vogel's work, but instead of producing one curve by conventional regression, I built three neural network models. Two models predict the IPR efficiently with higher overall accuracy than Vogel's reference curve.

This work provides a semi-analytical development of the pressure-mobility behavior of solution gas-drive reservoir systems producing below the bubble point pressure. Our primary result is the "characteristic" relation which relates normalized (or dimensionless) pressure and mobility functions. This formulation is proven with an exhaustive numerical simulation study consisting of over 900 different cases. We considered 9 different pressure-volume-temperature (PVT) sets, and 13 different relative permeability cases in the simulation study. We also utilized 7 different depletion scenarios. The secondary purpose of this work was to develop a correlation of the "characteristic parameter" as a function of rock and fluid properties evaluated at initial reservoir conditions such as: API density, GOR, formation volume factor, viscosity, reservoir pressure, reservoir temperature, oil saturation, relative permeability end points, corey exponents and oil mobility: We did successfully correlate the characteristic parameter as a function of these variables, which proves that we can uniquely represent the pressure-mobility path during depletion with specific reservoir and fluid property variables, taken as constant values for a particular case. The functional form of our correlation along with all relevant equations are shown on the body of this document.

[pt] Para que ocorra o fluxo de fluidos em um sistema de produção é necessário que a energia dos fluidos no reservatório seja capaz de superar as perdas de carga nos diversos componentes do sistema. Os fluidos têm que escoar do reservatório aos separadores na superfície, passando pelas tubulações de produção dos poços, pelos equipamentos de cabeça de poço e pelas linhas de surgência. O projeto de um sistema de produção não deve ser executado considerando independentemente o desempenho do reservatório e o cálculo do fluxo nas tubulações de produção e nas linhas e equipamentos de superfície. A avaliação do desempenho de um sistema de produção de gás requer a aplicação de um método de análise total que considere simultaneamente o escoamento nos diversos segmentos do sistema. A análise total de um sistema de produção, pode ser efetuada por um método gráfico - analítico a ser empregado no desenho de completação de poços de gás e petróleo com ou sem levantamento artificial. Em termos de conceito de análise total, um sistema de produção é constituído basicamente pelos elementos: reservatório, tubo de produção vertical, linhas de fluxo horizontal e separador, incluindo válvulas de fundo de poço e choke superficiais, onde ocorrem uma certa perda de pressão relacionada com a vazão. O comportamento de fluxo de cada elemento do sistema total de produção é representado por uma equação que relaciona a pressão num nó selecionado e a vazão de produção. O cálculo seqüencial das pressões nos diferentes nós dos diversos elementos do sistema permite que a vazão de produção do poço seja determinada. Para calcular a relação da vazão com as mudanças de pressão que ocorrem durante o transporte do fluido à superfície e conseqüente variação das propriedades físicas do fluido, efetuou-se uma revisão dos conceitos de engenharia de reservatório, correlações de fluxo em tubulações verticais, horizontais e restrições. Finalmente, realizou-se uma análise de sensibilidade da metodologia ao emprego das diferentes relações de performance de fluxo e dos métodos de cálculo de fluxo em poços e linhas. / [en] For the flow of fluids to occur in a production system, the fluids energy in the reservoir must be capable of overcoming load losses along various system components. Fluids must flow from the reservoir to the surface separators through the wells tubing, wellhead equipment and flowing lines. The production system design must not be executed by considering separately the performance of the reservoir and the flow calculation across the tubing, surface equipment and lines. The evaluation of a gas production system performance requires applying a total analysis method that considers the drainage at various system segments simultaneously. The total analysis of a production system can be effected through a graphical- analytical method to be used for the completion design of oil and gas wells with or without artificial lift. In terms of total analysis concept, a production system is basically comprised of the following components: reservoir, vertical tubing, horizontal flow lines and separator, including bottom-hole valves and surface choke, where some pressure loss occurs in relation to the flow rate. The flow behavior of each component in a total production system is represented by an equation that relates the pressure at one selected node and the production flow rate. The sequential pressure calculation at the different nodes of various system components allows determining the well s production flow rate. In order to calculate the relationship between the flow rate and the pressure changes that occur during fluid transportation to the surface, with the resulting variation of the fluid s engineering, flow correlations in vertical and horizontal tubing, and restrictions. Finally, we proceeded to analyze the methodology s sensitivity to the use of different flow performance relations and flow calculation methods in wells and lines.