A Novel Method for Life-Cycle Production Performance Forecast Based on Dynamic Analogs
Authors: Lu Xiaoguang , Sun Shao-Qing , Xu John , Wu Wenkuang , Zhai Pengyuan , Wei Yunan , Li Guoqiang 
Published: May 2016

Abstract
Conventional production performance forecast by reservoir simulation is very time-consuming. Another major drawback of such an approach is the huge uncertainties in the forecast results owing to data limitation, especially at the field appraisal and development planning stages. As an efficient alternative to reservoir simulation, a novel life-cycle performance forecast method is developed which integrates dynamic information from analog reservoirs with decline curve analysis. The output of the forecast provides essential information for field development planning. This includes water breakthrough timing, duration of typical development phases (developing, plateau, decline and mature), number of active producers, oil rate and water-cut. Other important dynamic performance indicators, such as water production rate, WOR, cumulative production, remaining reserves, recovery efficiency, URR and ultimate recovery factor, which are related to economic evaluation and facilities design, are also derivable.
The prerequisite for application of this method is possession of sufficient dynamic information from a large number of mature or abandoned fields, which can be selected as the analog fields. The analog fields ought to have similar characteristics to the target forecast field in terms of trap, reservoir, fluid properties and initial in-place hydrocarbon volumes. Key parameters for selecting analog fields include sedimentary environment, sandbody type, range of reservoir permeability, oil API gravity, viscosity, possible STOIIP, and drive mechanism.
The new method can be applied to:fast-evaluation of new assets - the forecast result can be used as direct input for economic evaluation;uncertainties estimate in decision-making process using the forecasted low-, medium- and high-case scenarios;verification and uncertainty reduction for conventional reservoir simulation by comparison with the analog based forecast results; andmature asset benchmarking in order to identify new opportunities to improve recovery.Using tailor-developed software, the process of analog forecast can be completed efficiently within minutes. The forecast is based on real-world facts and has taken into consideration of key factors that influence actual field development. Therefore, the forecast by the new method is, to certain extent, more approximate to the real field production history.

Introduction
Analogs have been widely used in the oil industry and are becoming increasingly important. Major applications include resource estimates, recovery factor forecast and IOR application benchmarking. SPE, AAPG, WPC and SPEE (2010) regard the analogs approach as one of three analytical procedures for estimating recoverable quantities, parallel with volume estimates and performance-based estimates. Although analogs are particularly applicable in the exploration and early development stages, when direct measurement data is scarce, it has been realized that review of analog reservoir performance is useful for quality assurance of resource estimates in all stages of field development.