The Estimation of Productivity Loss Caused by Perforations - Including Partial Completion Perforations - Including Partial Completion and Formation Damage

This paper was prepared for the Second Midwest Oil and Gas Symposium of the Society of Petroleum Engineers of AIME, to be held in Indianapolis, Ind., March 28–29, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication is the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication is the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

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Abstract

New methods for calculating well productivity are presented that account for the productivity are presented that account for the combined effects of partial completion, formation damage, and perforations more accurately than methods previously used. Completion effectiveness is highly sensitive to damage and partial completion when perforations are involved. The analytically developed equations given here can be used in designing more effective perforation programs for new well completions and in identifying wells where production rates can be improved through production rates can be improved through workover procedures. The equations provide simple multiplying factors that correct results from previous perforation productivity charts for previous perforation productivity charts for partial completion and damage. Applications of partial completion and damage. Applications of this work show that the effects of combined restrictions to flow are compounded in producing oil or gas wells. Thus, a combination of modest flow restrictions causes a much greater loss of production than is predicted by previous production than is predicted by previous calculational methods.

Introduction

Over 20 years ago, McDowell and Muskat, calculated production loss through perforations in fully completed pay formations. They considered a number of variables, including number, size, depth, and geometrical location of perforations. More recently, Harris confirmed perforations. More recently, Harris confirmed and extended the previous work. These authors made a considerable contribution to the analysis of well completions. However, their studies did not provide a complete answer because the synergistic effects of combined flow restrictions were not known at that time.

This paper considers the analysis of completions where combined flow restrictions are present. When any combination of formation present. When any combination of formation damage, partial completion, and perforations is present in a completion, the flow restrictions present in a completion, the flow restrictions caused by the individual completion factors are compounded. Except in one case, these compound effects have been overlooked by the petroleum industry. This work provides the practicing engineer with equations for calculating compound effects. Examples are given to show their relative importance and application in design of well completions.

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