Decline Curve Analysis of Oil Production in Low Permeability Reservoirs with Great Heterogeneity

Abstract

There have been many models of decline curve analysis in estimating reserves and production in petroleum reservoirs. It is difficult to evaluate the models because the true value of reserve in oil reservoirs is usually unknown. Previously, comparison and analysis among limited models has been made using spontaneous imbibition data. In this study, an approach to using core flooding experimental data was proposed to verify and evaluate the decline curve analysis models. Four representative models (exponential, hyperbolic, harmonic, and the mechanistic Li-Horne models) were chosen to predict and match the oil production in low permeability core samples and oil reservoirs. A systematic comparison among the four models was conducted by using the sum of squared residuals, regression coefficient, and the true values of reserve (for core samples) as the evaluation parameters. Both experimental and reservoir data from a low permeability oil reservoir with great heterogeneity were used. It was found that it was difficult to appraise the goodness of the decline curve analysis models by using the sum of squared residuals and regression coefficient as judging parameters in some cases. The small values of the sum of squared residuals or the great values of the regression coefficient could not guarantee small error in the predicted reserves. It may be a suitable approach to using experimental data of oil production in core samples with different permeability to evaluate decline curve analysis models. The results demonstrated that the Li-Horne model and the exponential model predicted the reserves satisfactorily for experimental data of water flooding in the core samples with low permeabilities. Introduction It is still a challenge to predict the oil production in low permeability reservoirs with great heterogeneity, even using numerical simulation technique. Another frequently used approach is decline curve analysis. There have been many models of decline curve analysis in estimating reserves and production in petroleum reservoirs. However many of the existing decline curve analysis models are heuristic and are based on the empirical Arps equations (1945): exponential, hyperbolic, and harmonic models. The exponential decline curve tends to underestimate reserves and production rates; the harmonic decline curve has a tendency to overpredict the reservoir performance (Agbi and Ng, 1987). There have been many reports on decline curve analysis (Palacio and Blasingame, 1993; Masoner, 1998; Marhaendrajana and Blasingame, 2001; Lawal, et al., 2008). Fetkovich (1980) provided a theoretical basis for the Arps equation in the case of exponential decline where the exponential and harmonic models often work better at the later period of production than during the early period.

Non-Darcy Flow Numerical Simulation and Pressure/Rate Transient Analysis for Ultra-Low Permeable Reservoirs

“…It is known (see [2][3][4][5] and references given therein) that such reservoirs are characterized with low pressure gradients, and flow regime diverges from Darcy's law. For example, performance and analysis of laboratory experiments [2,3,4], influence of non-Darcy flow effects on oilfield development [5,7,9], numerical simulations of non-Darcy flow [3,4,6,8,10]. For example, performance and analysis of laboratory experiments [2,3,4], influence of non-Darcy flow effects on oilfield development [5,7,9], numerical simulations of non-Darcy flow [3,4,6,8,10].…”

Non-Darcy Flow Numerical Simulation and Pressure/Rate Transient Analysis for Ultra-Low Permeable Reservoirs (Russian)

“…Известно (см. Наблюдается увеличение количества публикаций, посвященных различным аспектам этой проблематики: выполнению и анализу результатов лабораторных экспериментов [2,3,4], влиянию нелинейных эффектов на процесс разработки [5,7,9], численному моделированию нелинейной фильтрации [3,4,6,8,10]. Этот эффект стал объектом пристального внимания со стороны специалистов нефтяных компаний и научноисследовательских институтов в России и за рубежом.…”