--> Abstract: Reservoir and Production Characterization in a Steep-Sided Upper Paleozoic Isolated Carbonate Platform Reservoir, Karachaganak Field, Kazakhstan, by David A. Katz, Ted Playton, Jerome A. Bellian, Paul M. Harris, Christopher Harrison, and Amisha Maharaja; #90124 (2011)

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Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Reservoir and Production Characterization in a Steep-Sided Upper Paleozoic Isolated Carbonate Platform Reservoir, Karachaganak Field, Kazakhstan

David A. Katz1; Ted Playton1; Jerome A. Bellian1; Paul M. Harris1; Christopher Harrison1; Amisha Maharaja1

(1) ETC, Chevron, San Ramon, CA.

Slopes of reef-rimmed carbonate platforms are depositionally complex due to a variety of deposit types that exhibit vertical and lateral variability. Karachaganak Field, northern Pricaspian Basin, Kazakhstan, is a Carboniferous isolated carbonate platform with a hydrocarbon column that resides primarily within foreslope strata. The distribution of reservoir properties has been poorly understood owing to the depositional heterogeneity of slope environments. These uncertainties were assessed by integrating seismic facies, outcrop analogues, cores, log data, and forward seismic models to produce a detailed depositional model that predicts compositional and architectural variability. Well lookbacks were also performed to assess the impact of carbonate foreslope characterization on well location and design in the current drilling program.

Seismic facies analysis with outcrop analogues and forward models reveals depositional regions within the stratigraphy that can be further divided into multiple styles of clinoforms, slope and basin sediment wedges, and margin configurations. Each of the seismic facies is defined by reflector characteristics, such as continuity, intensity, and geometry. Seismic mapping of the these elements with other subsurface data identifies heterogeneity at well, flow unit, and field scales, including 1) bedset-scale variations internal to clinoforms and wedges, 2) along strike and temporal variations in clinoform or wedge style, and 3) platform-scale asymmetry.

Integration of core and log data with outcrop analogues, allows for prediction of the depositional rock types and depositional regions within the stratigraphy mapped at Karachaganak. Spatial and stratigraphic trends in reservoir properties and connectivity were extracted from the reservoir model. This approach links seismic-scale architecture, petrophysical behavior, and geographic distribution, thereby providing insights for future reservoir development and modeling. For example, recent production data from the current drilling program shows that wells in the youngest Carboniferous slopes are the poorest producers due primarily to depositional heterogeneity - characteristics that the conceptual model and base case reservoir model predicts. Recent results from revised well trajectories based on recommendations made from this study were successful and validate both the conceptual geological and reservoir models.