This paper presents a knowledge-based system for designing matrix stimulation operations. The two main points in carrying out such a design are to define the technical/economic objectives to be reached and the injection parameters that optimize stimulation. The system takes into consideration these points and generates a matrix stimulation program that includes treatment, spacer and displacement fluids, operating procedures, equipment, reference injection parameters and, finally, diagrams to evaluate the removal of damage during the execution of the job. Expert knowledge has been formalized and implemented using a built-in-house classification shell. The system, preliminarily validated at company headquarters, has been delivered to the operating districts where it is routinely used. The system is part of a more comprehensive project, called PROGRESS (PRoduction Optimization inteGRated Expert SystemS), aimed at providing a decision support system for well production optimization.
Introduction
The goal of a matrix stimulation job is to minimize the effect of formation damage on the productivity of wells, taking into account technical and economical considerations.
A matrix stimulation job consists in injecting a chemicals mixture into the formation. The selection of appropriate chemicals and the design of accurate operating procedures for the job are tasks that only a few experienced technicians are able to carry out. Designing a matrix stimulation job is not only a difficult task, but also a delicate one: besides its cost, a wrong matrix stimulation job (i.e. a stimulation job that fails to remove the preexisting damage) could make the damage worse and possibly irreparable. The effort of developing a matrix stimulation support system is mainly aimed at reducing this risk to a minimum.
According to previous considerations, the Matrix Stimulation Design Expert System is used:as a support tool in operating districts when experts are not available. This tool reaches the following objectives:–supports the diffusion of techniques and gives operating personnel more technical autonomy;–encourages standardization in matrix stimulation design by distributing the techniques most recently developed by specialists;–allows experts to dedicate more time to studying new techniques by reducing their involvement in routine problems;as a framework where strategic know-how can be stored;as a training tool for new personnel.
The system presented in this paper is one of the four integrated systems of the PROGRESS project (fig. 1) aimed at providing a support tool for well production optimization. The Well Problem Analysis Expert System supports the user in verifying the existence of a production problem and in identifying its possible causes. If formation damage is thought to be one of the causes of well problems, the Formation Damage Expert System helps the user to diagnose the types of damage mechanisms. Once these mechanisms have been diagnosed, the Risk Analysis Expert System performs an a priori evaluation of the economical, technical and logistic risks associated to a matrix stimulation operation. Finally, when the total risk of the matrix stimulation job is thought to be low, the Matrix Stimulation Design Expert System generates an appropriate job program. The architecture of the PROGRESS project has been designed to allow the user to interact with the systems following the above flow or by individually consulting each system.
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