Pressure Analysis for Horizontal Wells

Abstract

Abstract This paper presents horizontal well test design and interpretation methods. New analytical solutions are developed, which can be easily handled by a desktop computer, to carry out design as well as interpretation using semi-log and log-log analysis. These analytical solutions point out a distinctive behavior of horizontal wells which is :- At early time, a circular radial flow in avertical plane perpendicular to the well.- At late time, a horizontal pseudo-radial flow. Each type of flow is associated with a semi-log straight line to which semi-log analysis has the adapted. The horizontal pseudo-radial flow takes into account a pseudo-skin depending on system geometry which is a priori defined and estimate Practical time criteria are proposed to determine Practical time criteria are proposed to determine the beginning and the end of each type of flow and provide a guide to semi-log analysis and well test design. We study the behavior of uniform flux or infinite conductivity horizontal wells, with wellbore storage and skin. The homogeneous reservoir is infinite or limited by impermeable or constant pressure boundaries. pressure boundaries. A method is also outlined to transform all our solutions for homogeneous reservoirs into corresponding solutions for double porosity reservoirs. 1 - Introduction The first horizontal producing wells yielded extremely positive results These results made it necessary to study flow around a horizontal well with a view to practical applications : test design and interpretation. The purpose of this study is to provide, with a horizontal well configuration a way :- to decide upon whether a test has to be made ornot : will the test help to obtain the requiredinformation ?- to optimize test time, if necessary : test mustbe long enough to be interpreted.- to interpret the test performed usingapplicable methods. The simplest and most significant analytical approach is first described in this paper. It relates to the transient behavior of a well with no wellbore storage C and no skin S, with a uniform flow (flow per unit length is the same everywhere in the well). Then the wellbore storage, the skin and the effect of the boundaries of the reservoir are taken into account, leading to a practical approach applicable to most real cases. The transposition of these solutions to infinite conductivity wells is described.