Design and Diagnosis of Deviated Rod-Pumped Wells

Abstract

Summary A wave equation method is presented for the design of deviated rod-pumped wells. Applications made to wells involve bare rods, molded-on guides, and wheel-rod guides. The design method is also used to explain the type of errors that result when vertical-hole techniques are used to compute down hole pump cards in crooked wells. Introduction Commonly used methods for designing rod-pumping installations presume vertical wells. This paper introduces a wave equation methodology that applies to deviated wells, whether they are deviated intentionally or unintentionally. Restrictions on surface locations and interest in horizontal drilling are increasing the need for deviated wells. Together with long-standing crooked-hole problems, these are promising subjects for further study. This paper describes a predictive method that applies to 3D problems. A well deemed too crooked to pump is studied, and a procedure for designing intentionally deviated wells is presented. The relative friction effects of rod guides are discussed, and the effect of borehole path on power consumption is treated. The concept of dogleg severity is examined and deemed inadequate as a measure of difficulty in pumping deviated wells. The types of errors that result when vertical-hole diagnostic methods are applied to deviated holes are discussed. Finally, a new formulation of the radius-of-curvature concept is derived together with techniques for deducing rod-tubing friction from dynamometer valve checks. Comparisons with actual measurements are included to validate the methods. Deviated wells can be adequately designed with wave equation methods, and highly deviated wells can be produced with rod-pumping equipment when care is taken to control the path of the borehole. This paper should be considered as a progress report because much remains to be learned about the application of this technology.