Development of an Expert System for EOR Method Selection
Authors: Shindy A.M. , Darwich T.D. , Sayyouh M.H. , Osman Abdel-Aziz 
Published: December 2007

Non-conventional enhanced oil recovery (EOR) methods are expected to be applied in a number of Egyptian oil fields in the near future. Human expertise and the results of previous applications world wide are indispensable in the the decision-making process of selecting the most feasible EOR method. This paper presents the current development of a knowledge-based expert system for the selection of the EOR method in petroleum reservoirs. The development of this system involved the following stages:Knowledge Acquisition: This has been achieved through a comprehensive literature review of the successful EOR recovery projects world wide coupled with experimental results from previous and current research activities at different research institutions and organisations. A new analysis method based on statistical evaluation has been used to produce the rules used in the expert system formulation.System Formulation: The acquired knowledge from the first stage has been coded using a computer program. This involves the representation of the acquired knowledge through rules. These rules are divided into separate and identified groups in order to facilitate the search of the rules, and their removal from or addition to the knowledge base.System Verification and Validation: This has involved the analysis of the consistency of stored knowledge and accurately reproduce the strategies used by experts and available in the literature to solve the problems of selection of EOR technique for different circumstances.

It is believed that with such a system an engineering judgment that stems from knowledge and experience will be available to sort, process, analyse and cross-refer the acquired reservoir data. Coupling this with other sources of information will allow us to achieve the most feasible selection of EOR techniques for Egyptian oil fields and allow for an efficient and profitable operation of oil reservoirs.

Introduction

The use of reservoir energy to produce oil and gas generally results in a recovery of less than 50% of the original oil in place depending on reservoir characteristics and the primary recovery mechanisms. A variety of supplemental recovery techniques have been developed to enhance the recovery factor obtained by utilising only the natural forces present in the reservoir. These supplemental recovery methods may be classified into conventional secondary recovery techniques - water injection and gas injection - and tertiary recovery methods such as miscible displacement, thermal recovery, and chemical flooding. However, because some of these processes may be applied early in the life of a reservoir, the "tertiary" term is no longer appropriate. Therefore, the term "Enhanced Oil Recovery" (EOR) has been used to refer to the non-conventional oil recovery methods - other than waterflooding and gas injection - that give additional production resulting from the introduction of artificial energy into the reservoir.

Enhanced oil recovery (EOR) methods may be divided into two main categories: thermal and non-thermal displacement processes. Thermal recovery methods include hot fluid injection methods (steam or hot water) and in-situ combustion (forward or reverse combustion) methods. Non-thermal recovery methods - or improved fluid-injection methods - may be divided into immiscible displacement processes (e.g. polymer and surfactant flooding) and miscible displacement processes (e.g. microemulsion flooding, CO2, and miscible gas injection). P. 291