Ever since the Bahrain field was discovered in 1932, the main focus of effort was on major formations of the field, leaving shallow formations not fully exploited. Today with the increase in oil price and the depletion of major formations, there is a greater preparedness to consider increasing production from these under developed zones.This case study was initiated with the purpose of increasing production from the Magwa zone, which is the most economically attractive of the shallow zones. The zone is the basal member of the Rumaila formation of the middle Cretaceous Wasia group. It is predominantly limestone with interbeded shale.This case study shows an integrated methodology to enable a better understanding of the reservoir production behavior and to explain the lateral heterogeneity of the formation. This investigation was triggered by the variation in the formation water salinity from North to South. Water saturation maps, production history, geochemistry and structure set-up were used as the main input in this analysis. The interpreted relations and trends between these factors were used to explain the behavior of the reservoir. The outcome of such investigations is of critical value in determining the location of new development wells, selecting candidate wells for workover and for EOR processes. This paper will explain how a better understanding of the reservoir through data integration has resulted in a significant increase in oil production.

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Bahrain has begun exploring unconventional resources in the Khalij Al-Bahrain Basin for the Tuwaiq Mountain Formation. This work is a case study presenting the workflow for characterizing and modeling the unconventional development in Bahrain all the way from petrophysics through geology, completion modeling, and dynamic simulation. The work scope consisted of petrophysical modeling 10 key wells including calibration to core data. The petrophysics showed that the lower Tuwaiq Mountain interval with its TOC signature is remarkably consistent across all of Bahrain. The wells modeled in a 3D geological model with reservoir properties distributed throughout the reservoir to confirm resource in-place estimates published in early 2018. Well stimulation treatment on Well 1 was modeled and tied to the production test. A dynamic model was subsequently built to history match the production test. While not unique in its production match, this calibration is an important step for future optimizations in lieu of microseismic data. All of this information was used to form the basis for optimal completions to refine the next appraisal wells with forecasted production rates. The Tuwaiq Mountain reservoir has commercial potential in Bahrain, particularly in the western area where producibility has been proven. Producibility in the East has not been established as no production tests are available. In addition, future appraisal well locations were identified using the 3D geological model. The best trajectory was chosen such that the wells are estimated to yield EURs more than 500,000 bbls. The results of this project are important for Bahrain as it highlights the unconventional resource and production potential in the country. For the industry, unconventional development is in its early stages outside of North America and Bahrain’s case study can be utilized to expedite the learning curve in many other basins.

The Unayzah formation is a nonmarine siliciclastic unit. It consists of massive quartzose sand to argillaceous sandstone, silty sandstone, siltstone, mudstone, and minor carbonaceous shale. The Unayzah is typically 300-350 ft thick at Awali. The Unayzah consists primarily of braided stream and related floodplain deposits. The depositional model includes flood plain deposits, meandering channels, point bars and alluvial fans. Six Lithostratigraphic units were identified based on the log character in the Unayzah sequence. These units are named as U1, U2, U3, U4, U5 and U6 from top to bottom.Impedance contrasts at the top Unayzah gas reservoir are strong enough to generate a negative reflection at the interface and the resultant amplitude can be directly related to reservoir porosity. This was confirmed by evaluating 1-D forward modeling (synthetic seismogram) results from several wells in the study area. The reflection response was validated in 3-D seismic data by a sharp negative reflection at the top of Unayzah reservoir with good correspondence between reflection intensity and reservoir quality as observed at well penetrations. This study is to test the above mentioned method in the flanks of Awali structure outside the known production area.