A Method for Probabilistic Forecasting of Oil Rates in Naturally Fractured Reservoirs

摘要

A method is presented for probabilistic forecasting of oil rates in naturally fractured reservoirs (NFRs) based on a new modified Darcy equation. The equation includes variables that have significant impact on productivity of NFRs such as matrix and fracture permeabilities, partitioning coefficient, i.e, the ratio of fracture and total porosity, and thickness of the perforated interval. To perform the calculations, probability distributions are generated for each one of the above input variables. The locations of the water-oil and gas-oil contacts are determined, as well as the maximum efficient oil rates to avoid premature coning of water and gas. The integration of these data with the modified Darcy equation leads to prediction of maximum, most likely and minimum oil rates that could be anticipated for production wells in different parts of the reservoir. The difficulties and uncertainties that exist for predicting oil rates in NFRs are widely recognized. The proposed methodology looks to diminish this uncertainty with a view to generate reliable production forecasts, optimize oil rates, improve oil recovery and maximize economic returns. The modified Darcy equation for NFRs discussed in this paper is not presently available in the literature. The equation is easy and rapid to use statistically, and is being applied in practice with a good level of success. Thus, it provides a valuable supplement to numerical simulation and a significant reservoir engineering tool in those instances where operational decisions must be made quickly.