Summary

When compared with hydraulic fracturing, matrix stimulation has a very high failure rate. This paper describes the development and field testing of a matrix-stimulation field-monitoring system designed to provide real-time control, optimization, and post job evaluation of matrix treatments. Using calculated bottomhole pressures (BHP) or coil-tubing/tubing-annulus reflected pressures, the system predicts pretreatment damage or skin from a step-rate test, then shows the evolution of skin removal vs. treating fluid volume or time. The system provides real-time information to the operator conducting the treatment about when to drop diverter, treating fluid efficiency, and diverter efficiency. The system can also be used to estimate treatment height and damage radius. Input data can come directly from the service company's digital sensors or from separate sensors placed in the treating line. A description of the system and several case histories showing its utility are presented.

Introduction

The economic success of a stimulation treatment often cannot be evaluated until after several weeks or months of production, following cleanup of the well and recovery of the injected fluid. The initial evaluation of the engineering design must be made from data obtained on site either immediately before the treatment, during pumping, or immediately following shutdown. Since the early 1980's, advances in monitoring stimulation treatments have included the use of microcomputers to gather digital data records.

This technology is widely used in hydraulic fracturing to calculate bottomhole treating pressures, to determine formation response to the treatment, and to model the growth of hydraulic fractures. Techniques to analyze pressure-falloff data and pressure data obtained during the treatment have found widespread application.

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