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Abstract

Increased efficiency in production operations requires that the formation and completion characteristics be well defined and analyzed before committing funds to stimulation and/or workover operations. Such information is generally obtained from analysis of pressure transient data measured with wireline recorders. Until recent times, these measurements have been seldom made in pumping wells, due to the time required to trip the rods and pump out of the tubing in order to run the wireline pressure recorders. This need spurred the development of techniques for calculation of transient bottomhole pressure from surface measurements. pressure from surface measurements. This paper describes the design and application of a fully digital system for automatic calculation of bottomhole pressure from echometric surveys of the annular fluid level. This portable system integrates specially designed high resolution A/D conversion and conditioning with advanced signal processing and digital filtering techniques. This results in very accurate determination of the depth to the fluid level, even in the presence of background noise caused by gaseous presence of background noise caused by gaseous liquid columns.

Automatic signal generation and recording is undertaken by the software at predetermined, operator selected frequency so as to maximize the quality of the pressure transient data. Surface pressure and pressure transient data. Surface pressure and temperature measurements are used in conjunction with gas gravity and gas acoustic velocity to determine the pressure at the gas/liquid interface and the pressure at pressure at the gas/liquid interface and the pressure at the sandface.

Graphic displays allow the operator to monitor the progress of the transient test by plotting in real time the progress of the transient test by plotting in real time the current status of the well, the acoustic signals and the calculated pressures. Data that has been acquired at that point can be plotted as standard transient analysis graphs (Homer, MDH, Log-Log etc.) Data files can be exported to other analysis programs.

Introduction

The present economic climate in the oil industry requires that maximum production efficiency be achieved with minimum engineering and technical manpower. Considering that the majority of US land oil wells are produced through artificial lift and the majority of these by means of beam pumping systems, it becomes apparent that there exists an increasing need to easily monitor and analyze the performance of beam pumped wells. pumped wells. Flowing bottom hole pressure surveys, pressure buildup tests, pressure drawdown tests, and inflow performance analyses are the principal tools available performance analyses are the principal tools available to determine reservoir pressure, formation permeability, productivity index, pump efficiency, skin factor, as well productivity index, pump efficiency, skin factor, as well as other indicators that can be used in the optimization of producing well operations. These techniques are widely used in flowing wells and in some gas lift wells, where the pressure information is easily obtained from wireline-conveyed bottom hole pressure recorders. The presence of the sucker rods in beam pumped wells presence of the sucker rods in beam pumped wells essentially precludes practical, routine, direct measurement of bottomhole pressure, thus eliminating the single most important parameter for well analysis. Permanent installation of surface indicating bottomhole Permanent installation of surface indicating bottomhole pressure gages have not become cost effective, nor pressure gages have not become cost effective, nor have wireline measurements through the annular space.

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