Data Validation: Key to Development of an Integrated Reservoir Model for the Wara Formation, Greater Burgan Field
Authors: Pederson John M. , Moon Mark S. , Al-Ajeel Haifa 
Published: December 2007

Prior coarse grid simulation models in the Greater Burgan field were unable to capture the stratigraphically diverse nature of the Wara reservoir, and accurately match the existing historical data, resulting in unrealistic predictions of fluid flow from individual reservoir layers. Most simulation failures are blamed on the inability to correctly model reservoir heterogeneity, rather than problems associated with the data it is trying to match. In reality it is probably a function of both. This paper emphasizes the importance of a systematic review of historical production data to assure the accurate initialization of a simulation model and to assess if a full history match should or should not be undertaken.

Not only does there need to be sufficient geologic and engineering detail to accurately characterize the fluid and flow properties of the Wara reservoir, but more importantly issues involving the validity, accuracy, and lack of historic data need to be addressed, before deciding whether a reasonable reservoir model for history match could be developed. The reservoir size, long history, and high production rates of the Greater Burgan field magnify the impact, and highlight the importance of correcting data errors, and recognizing data uncertainty and gaps.

Introduction

A reservoir simulation model is only as good as the data going into it. Data review and validation is necessary to understand the accuracy and limitations of the data and should always be the first step toward developing a successful reservoir simulation model. Results from a simulation based on inaccurate data may be more damaging to the planning and economics of developing a reservoir than not having a predictive simulation model at all.

A systematic review of the Wara production data in the Greater Burgan field identified data problems that have changed prior simulation assumptions about the reservoir character, flow characteristics, and reservoir drive mechanisms. These results will help improve the history match and therefore the accuracy of future development prediction cases.

Previous simulation studies in the Greater Burgan field identified the need for more pressure support in the Wara reservoir than what the modeled aquifer could provide. The source of this pressure support has been modeled as fluid influx from the underlying Burgan formation through faults or vertical migration where shale and carbonate barriers between the Burgan and Wara reservoirs may be locally missing. The key to determining the need for this additional pressure support is the assumption that the reported historical production is correct and properly represents the actual volume of fluid produced from the Wara reservoir. Because production data is the primary factor influencing the fluid flow and pressure characteristics in a simulation model it is imperative that this data be reviewed, validated, and updated to be as accurate as possible. The aim of this paper is to show the impact to the initialization of a reservoir simulation model by using reported data without investigating it's accuracy or relationship to historical field practices. Companion papers highlight other aspects of the ongoing effort to characterize the Wara reservoir.

Background of the Wara Formation

The Burgan field was discovered in 1936 with drilling of the Burgan #1 well into the Wara formation. Several delineation wells were drilled prior to World War II but full scale field development did not occur until 1946 when the first production from the field was exported.

Production from the Greater Burgan Field has been primarily from the Wara and Burgan (third & fourth sand) reservoirs. P. 565