An Example Approach to Predictive Well Management in Reservoir Simulation
Authors: Stackel Andrew W. , Brown Harry M. 
Published: December 2007

A well management routine is software which controls the status of individual wells or groups of wells during a reservoir simulation. The salient features of a unique prediction routine used in areal reservoir studies are described, including (1) methods of explicitly predicting well rates and produced fluid ratios and (2) procedures for limiting or increasing total production or injection rates. The routine provides a logical framework for studying alternative operating plans while allowing users to change or eliminate specific constraints by means of data entry.

Introduction

A reservoir performance prediction study sometimes can become a trial-and-error process, since an engineer normally wishes to sustain assigned production and/or injection targets while staying within facility capacities and operating constraints. The engineer usually must estimate the production and injection levels which can be maintained from various wells during a period of time. If a simulation shows that rate estimates lose their validity during the predictive period, the engineer must refine his assumptions and repeat the prediction. Not only is this a time-consuming process, but there is also the possibility that the engineer might not always use the same logic as before when changing previous estimates.A well management routine is software designed to systematize the decisions and calculations that are required during a prediction simulation. Its primary purpose is to allow long predictions to be made with a minimal need for manual interruptions. To accomplish this objective the routine must (1) monitor the status and determine the capability of existing wells, (2) allocate production and injection targets to any well or group of wells while honoring facility capacities and other operating constraints, (3) work over or shut in producing wells when necessary to stay within water/oil ratio (WOR) or gas/oil ratio (GOR) limits, and (4) bring new wells on stream as required to attain target rates. The program logic should duplicate actual decision-making processes as closely as possible and yet be flexible enough to permit a sensitivity study of important engineering factors by allowing appropriate controls to be altered or eliminated.Properly designed well management routines, along with accurate methods of modeling the characteristics of wells and surface equipment, can help to define the facility requirements necessary to implement a producing strategy. Facility requirements are a critical element in evaluating investment alternatives and determining the feasibility of an operating plan.This paper presents the major features available in a special-purpose well management routine used to predict the future performance of some of the largest Arabian reservoirs in a two-dimensional, three-phase areal simulator at Exxon Production Research. It outlines parameters and correlations which can be adjusted in any combination to model accurately a variety of surface facility configurations and producing strategies. Although most of the features were designed to study specific reservoirs in the Middle East, some of the approaches may be applicable in a more general sense.

Calculation of Well Capabilities

The foundation of any well management routine is its ability to determine the maximum fluid rate a well can attain at any given time.

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