Reservoir Evaluation and Deliverability Study, Bierwang Field, West Germany
Authors: Matthes G. , Jackson R.F. , Schuler S. , Marudiak O.P. 
Published: December 2007

To determine an optimum production strategy, an areal two-dimensional gas-water model, cross-sectional studies, and a coning model were used. history match showed appreciable horizontal water influx. Water coning, however, would not be a problem, and channeling could be overcome by additional perforating. Ultimate gas recovery can be considerably increased if withdrawal rates are kept high.

Introduction

Until imported gas is available in Bavaria, the present measure for filling the gap between present measure for filling the gap between increasing gas demand and diminishing gas reserves is to accelerate the gas recovery from existing fields. The dominant role of the Bierwang field is illustrated by the fact that in 1971 this field produced 28 Bcf of gas, or 59 percent of be total produced 28 Bcf of gas, or 59 percent of be total natural gas production of Bavaria. The field (Fig. 1) was discovered in 1964 with the drilling of Bierwang C2, which encountered several gas-bearing horizons. With respect to gas in place, the most interesting zone was the Chattian Main Sand, consisting of a well developed porous sandstone with a 105-ft hydrocarbon section. The Chattian Main Sand reservoir is a stratigraphic, structural trap with a porosity pinch-out due to an erosional pinch-out on the eastern edge and an impermeable fault boundary to the north and west. The downdip limit, to the south, is defined as a gas-water interface at 3,428 ft subsea. The original gas in place, determined dynamically and volumetrically, was about 156 Bcf. The gas is both sweet and dry, permitting this reservoir to be studied as a dry gas pool permitting this reservoir to be studied as a dry gas pool with an aquifer. The size and extent of the aquifer are not known reliably. However, the reservoir pressure behavior indicates the existence of a strong water drive with associated water influx. To the end of 1970, five wells were capable of gas production. However, one of these wells had exhibited water breakthrough and was producing with a continually increasing water cut. The objectives of this study were to determine the came of Ne water production, to predict the future deliverability of the reservoir, and to determine the expected ultimate gas recovery. The study was performed in three stages. The first part was a pressure history match of the reservoir performance to determine the extent of the aquifer influx and to confirm the estimate of original gas in place by material balance. The second stage was an investigation of all possible causes of water production. The third stage consisted of future deliverability studies to investigate pool capability to meet the gas demand and finally to determine the ultimate gas recovery resulting from an optimum development strategy.

Reservoir Pressure History Match

The Bierwang field was discovered in 1964, and sustained gas production began in mid-1967. (Fig. 2 shows the production history of the pool.) Annual pressure surveys have been conducted in the pool pressure surveys have been conducted in the pool since 1967. Individual well pressure history is available for the five producing wells and is given in Table 1. The pressures decline at a decreasing rate with cumulative production, revealing the existence of a water drive from the adjoining aquifer.

JPT

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