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The first phase of development of the viscous oil resources of Kuwait is planned to be delivered through cyclic steam and steam flood technology. A pilot plan to ensure optimum utilization of the injected heat and maximizing recovery from this resource is under implementation. The reservoir is layered and the level of communication between the zones is not fully understood. Careful planning in completion is needed in this complex reservoir, to obtain meaningful information for interpretation of the pilot results. The present study summarizes the methodology used to address this challenge.The complex layered nature of the reservoir along with possible free gas pockets poses serious challenge for the completion strategy. In this study, simulation history matching of the dynamic test data from the ongoing thermal and non-thermal pilots was used to interrogate the preliminary static description. The process resulted in an improved and reliable dynamic model, which was then used in the prediction mode, for deciding on an optimum completion strategy for the later steam flood phase.The study recommended Vertical Expansion Steaming and simultaneous steaming strategies to be used in different pilot areas. The nature of the ЉbaffleЉ zones between the oil bearing zones and their flow property under steam flood is considered an unknown factor, which needs careful evaluation in the pilots. The proposed well completion scheme is designed to address this subject.The study summarizes how the planned completion study would be used to interpret and utilize the pilot performance data, for optimizing cost and reserves of the commercial project. The different completion options that were evaluated in the study and their results should provide valuable knowledge for application in similar EOR projects.
The first phase of development of the viscous oil resources of Kuwait is planned to be delivered through cyclic steam and steam flood technology. A pilot plan to ensure optimum utilization of the injected heat and maximizing recovery from this resource is under implementation. The reservoir is layered and the level of communication between the zones is not fully understood. Careful planning in completion is needed in this complex reservoir, to obtain meaningful information for interpretation of the pilot results. The present study summarizes the methodology used to address this challenge.The complex layered nature of the reservoir along with possible free gas pockets poses serious challenge for the completion strategy. In this study, simulation history matching of the dynamic test data from the ongoing thermal and non-thermal pilots was used to interrogate the preliminary static description. The process resulted in an improved and reliable dynamic model, which was then used in the prediction mode, for deciding on an optimum completion strategy for the later steam flood phase.The study recommended Vertical Expansion Steaming and simultaneous steaming strategies to be used in different pilot areas. The nature of the ЉbaffleЉ zones between the oil bearing zones and their flow property under steam flood is considered an unknown factor, which needs careful evaluation in the pilots. The proposed well completion scheme is designed to address this subject.The study summarizes how the planned completion study would be used to interpret and utilize the pilot performance data, for optimizing cost and reserves of the commercial project. The different completion options that were evaluated in the study and their results should provide valuable knowledge for application in similar EOR projects.
A heavy oil field (Field X) in Northern Kuwait is in the early stages of development but it is clear from production pilots that tight units (baffles) of variable lithology, thickness and continuity, within the reservoir will play a key role in influencing steam conformance and recovery efficiency. The high well/core density of the field’s production startup area allows re-evaluation of baffles in light of cross-discipline integration of pilot production data, petrophysical data and detailed core review. A process was followed to update and calibrate all core descriptions against logs, follow a consistently picked set of petrophysically defined markers, compare visually defined lithofacies with log defined ones, and then map out key surfaces. The key next step is to define appropriate reservoir properties by facies/rock types, apply these to understanding pilot behaviour and predict steam conformance for Well, Reservoir and Facilities Management (WRFM) and the next phases of the wider field development planning. The field’s baffles play a role far beyond just understanding steam conformance, they are a first barrier for cap rock integrity and their presence/absence will also influence the path and rate of the aquifer influx. The petrophysical redefinition (Baffle Quality Index) of a "semi-stratigraphic" interval - which will stop or slow steam migration depending on its quality and lateral extent - has enabled efficient communication about the baffle, and allowed the wider team of petroleum engineers from a number of subsurface disciplines to focus on dynamic properties impacting recovery – steam conformance, aquifer influx, windows between isolated reservoir units – and then evolve the development strategy, effectively respond to WRFM issues, optimize observation and infill well placement and increase UR in a cost effective way.
Within North Kuwait heavy oil fields, integrated reservoir modelling is challenged by inherent reservoir heterogeneities, regional non-stationarity (i.e. trends), asymmetrical well and seismic distributions, and the need to maintain alignment between various the model scales required and multiple purposes for which the models will be used. This paper presents a number of customized workflows adapted to characterize these reservoir architectures and heterogeneities within one field, appropriately at all model scales and in regions with variable well control. A reliable new rock type classification scheme was derived from cross plot analyses of Gamma Ray and Bulk Density (GR-DENS) logs. Within an initial production area containing over 900 regularly spaced wells, 3D variograms for these lithotypes were estimated, calibrated with 3D seismic and reservoir equivalent surface outcrops. The lithotypes were distributed into full field static models using these variograms and the Sequential Indicator Simulation (SIS) algorithm. An additional declustering step was implemented to express regional trends and account for asymmetrical data distribution. Petrophysical property modeling (shale volume, effective porosity, water saturation) was performed using the Kriging algorithm conditioned to lithofacies. From these full field models, sector models were created to capture geological heterogeneity at a smaller grid increment. Full-field facies were downscaled onto the sector model grids, and then the Sequential Gaussian Simulation (SGS) algorithm was used to interpolate petrophysical properties, constrained by histograms of the kriged background models. This allowed information from wells outside of sector models to be incorporated efficiently into them. The facies and heterogeneities represented within the full-field static models have improved upon earlier versions, by being distributed more consistently relative to known seismic and well control, and to outcrop reservoir analogues. Modelled petrophysical properties also show a more consistent linkage with known values derived from core analyses. This consistent set of models can now be used with greater confidence, to answer questions ranging from in-place volume uncertainties to dynamic production forecasting, to life of field development. This has also led to reduced dynamic model run times, and improved reservoir management and operations optimization. In summary a robust series of full-field and sector models was developed and customized to a North Kuwait heavy-oil field, with information from data-rich areas being elegantly applied to reduce uncertainties in data-poor areas. These nested models can now be matched to the detail required for the model purpose. For example heterogeneities that matter-for-flow in dynamic simulation models can be represented explicitly, whereas for full-field volume estimations property averages can be used.
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