Permeability Model Conditioning of a Thin, Heterogeneous High-K Dolomitized Unit in a Supergiant Carbonate Field, Offshore Abu Dhabi
- Kazuyuki Yamamoto (Zakum Development Co.) | Gary Kompanik (ZADCO) | Ken Brantferger (ZADCO) | Osama Al Zinati (ZADCO) | Gary Ottinger (ZADCO) | Abdulla Al Ali (Zakum Development Co.) | Scott Dodge | Henry Ewart Edwards (Zakum Development Co.)
- Document ID
- Society of Petroleum Engineers
- Abu Dhabi International Petroleum Conference and Exhibition, 11-14 November , Abu Dhabi, UAE
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 5.6.1 Open hole/cased hole log analysis, 5.1.5 Geologic Modeling, 5.1.2 Faults and Fracture Characterisation, 4.1.5 Processing Equipment, 1.6 Drilling Operations, 1.6.9 Coring, Fishing, 5.6.4 Drillstem/Well Testing, 5.8.7 Carbonate Reservoir, 5.4.1 Waterflooding, 5.5.8 History Matching, 6.5.2 Water use, produced water discharge and disposal, 4.1.2 Separation and Treating, 4.3.4 Scale
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This paper presents a method to condition the permeability modeling of a thin, heterogeneous high-K dolomitized unit. The interval is an important drilling target for field development, so precise permeability modeling is required to optimize well placement and completion designs in order to maximize oil recovery and minimize early water breakthrough.
Detailed core observations from 85 wells classify the unit into two groups: Group A, composed mainly of dolostone and Group B, comprised exclusively of calcareous dolostone. Regression analyses of plug porosity-permeability values are characterized by one regression line for each group by which dolostone represents a higher permeability trend relative to calcareous dolostone. Core-plug scaling is used to scale-up the porosity-permeability relationships from core plug- to model-scale (100 m by 100 m cells). The two regression lines accurately capture the permeability contrast within the dolomitized unit.
To extend the method into a full-field model, it is necessary to calibrate the well logs to the core data. Comparison of cores with various log responses indicates the porosity log is the most useful tool to achieve this. Group A, characterized by higher dolomite content, is distinguished by a distinct decrease in the porosity due to progressive dolomitization.
Porosity logs from 499 wells are interpreted and permeability values are assigned using the regression lines based on the detailed distribution map of both groups. The modeling approach using hundreds of well logs calibrated to cores yields a more detailed picture of the spatial permeability variations of the dolomitized unit. Dynamic data from ongoing history matching is also used to implicitly adjust the first-pass static model.
The field has been historically developed utilizing a five-spot pattern water-flood and the studied dolomitized unit is one of the important drilling targets. The unit is 3.5 feet in average thickness and generally has higher permeability values than surrounding limestones. A massive field development plan is currently underway and a large number of long laterals will be placed in the dolomitized unit (Fig. 1A). However, potential risk of water injection breakthrough in this higher permeability reservoir unit is an important uncertainty. Precise permeability modeling of the dolomitized unit is critically required for the completion designs in order to enhance productivity and mitigate the potential risk of water injection breakthrough. A study including detailed core observations from 85 wells has been carried out (Fig. 1B) which classifies the dolomitized unit into two groups: Group A, composed mainly of dolostone and Group B, comprised exclusively of calcareous dolostone (Fig. 1C) (Yamamoto et al., 2011). Regression analyses of plug porosity-permeability values are characterized by two different regression lines: "Trend 1?? for dolostone, which represents a higher permeability trend and "Trend 2?? for calcareous dolostone, which represents a lower permeability trend (Fig. 1D). The proposed method for permeability modeling better captures the permeability contrast within the dolomitized unit and characterizes high-K dolostones much more precisely than using a single regression line used in the previous model (Fig. 1D). However, the proposed concept is only applicable to core data which are sporadically distributed in the field (Fig. 1B). In order to apply the presented method to a full-field geological model, it is necessary to extend the dataset into numerous uncored wells. In this paper, a well-formulated method is presented to condition permeability modeling of a thin, high-K dolomitized unit, utilizing porosity logs from 499 wells densely-distributed throughout the field.
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