Abstract

This paper presents a case study on a reservoir simulation modeling of recycling gas condensate using Modified Black Oil formulation (MBO) to identify and recover the by-passed condensate in Al-Raja Field. Al-Raja field is a good candidate to utilize MBO formulation instead of fully compositional due to following reasons (1) Gas injection/recycling is able to maintain the reservoir pressure above or at the dew point pressure in Al-Raja Field. (2) by keeping reservoir pressure above dew point pressure, gas injection will prevent any Retrograde Liquid Deposit (RLD) occured in the reservoir. It was well accepted methodology that MBO can be used in lean to medium rich gas condensate reservoir under gas cycling above dew point.

Al-Raja field is located in the Eastern part of the Marib-AlJawf Basin Republic of Yemen. The field has a moderate-size medium rich gas condensate reservoir with an average gas production rate of 750 MMscf/D from 18 wells. The lean gas is being re-injected back into the reservoir using line-drive pattern wells. Some make up gas from nearby fields was provided to replace fuel and shrinkage volumes. The high vertical relief of the field structure leads to significant temperature gradient that resulted in challenges to model the oil-gas ratio (Rv). The primary objective of the study is (1) to evaluate the current gas recycling performance at well and field level, (2) identify the location of current by-passed condensate (3) utilize the model to improve and optimize the liquid recovery through several options of optimum field developments (infill wells).

To achieve the objectives, 3-D Static and Dynamic models with 4 components MBO definition were constructed. In this study, we will show how to generate PVT Modified Black Oil (MBO) properties such as solution gas-oil ratio (Rs), oil-gas ratio (Rv), oil formation volume factor (Bo), and gas formation factor (Bg), from PVT-EOS. Whitson and Torp procedures were selected to calculate MBO properties from PVT experimental data of gas condensate.

The use of the MBO approach enabled us to perform faster field performance history matching compared with the compositional. This approach preserves less run time to conduct the Al-Raja prediction including infill drilling optimization. The condensate-gas ratio distribution achieved after the history match process guided us to locate the optimum infill well locations in by-passed area for the future development. Moderate condensate areas were located, and several wells have been drilled and proved to be successful. More infill wells were recommended to raise the field production and recover the remaining reserve

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