Impact and Lessons of Using High Permeability Streaks in History Matching a Giant Offshore Middle East Carbonate Reservoir
- Kenneth M. Brantferger (ZADCO Petroleum Co) | Gary Kompanik (ZADCO) | Haitham Al-Jenaibi (ZADCO) | Scott Dodge | Harshad Patel (ZADCO)
- 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, 5.4.1 Waterflooding, 5.5.8 History Matching, 5.1.5 Geologic Modeling, 5.8.7 Carbonate Reservoir, 5.1.7 Seismic Processing and Interpretation, 1.1 Well Planning, 4.3.4 Scale, 1.6 Drilling Operations, 5.1 Reservoir Characterisation, 1.6.9 Coring, Fishing, 5.6.4 Drillstem/Well Testing, 3.3.1 Production Logging
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A new generation geologic model for a giant Middle East carbonate reservoir was constructed and history matched with the objectives of creating a model suitable for full field prediction and sector level drill well planning. Several key performance drivers were recognized as important factors in the history match; 1) unique carbonate fluid displacement; 2) data validation and horizontal well trajectory issues; and 3) distribution of high permeability streaks. Ultimately a full field history match consisting of more than 1000 well strings and several decades of history was achieved using detailed distribution of the high permeability streaks, while honoring measured core poro-perm relationships, lab-validated displacement curves, and well test data.
This paper discusses the role of the geometry and the vertical distribution of the high-permeability streaks in the history matching of a giant offshore carbonate reservoir. Specifically, the modeling of the high-permeability streaks - which consist of thin rudist and algal rudstone, floatstone, and peloidal grainstone, with abundant, well-connected inter-particle porosity - became possible after extensive revamping of the reservoir rock type model, updating well descriptions, and a detailed zonal mapping of the high permeability streaks and dolomitic zones. The areal and vertical model resolution was doubled over the previous models to accommodate the internal sub-layering of the upper four reservoir zones in order to capture the thin (~1.4 ft) high-permeability streaks.
During the history match, local modifications of the high-permeability streaks were the integral part of the feedback loop between the simulation engineers and geoscientists that kept the common-scale simulation model and geologic model synchronized. The final history match was validated by extensive analysis of the models' vertical conformance as compared to production logs. This approach made it possible to construct a more heterogeneous model than previous models; while honoring both field KH and matrix poro-permeability without local permeability multipliers. The combination of these features provides a higher confidence model of long term well injectivity/productivity.
The subject reservoir is a giant offshore carbonate reservoir deposited in an extensive, low to moderate energy, low-angle ramp setting that stack into an overall shallowing-upward carbonate depositional sequence. It is overall mud-dominated from the base of the reservoir to the middle zone and becomes grain-dominated from the upper portion to the top of the reservoir. Major reservoir rocks include: mud-dominated (mudstone and wackestone), packstone, grainstone, algal-dominated floatstone, rudist-dominated floatstone, dolomite, and a thin generic "high-permeability streaks?? in ascending reservoir quality.
The reservoir was operated under primary depletion for over a decade before being converted to a pattern waterflood and then eventually to a line drive as its current depletion plan. Recent field development activity necessitated constructing and history matching a new generation model using the lessons from the previous model and emphasis on understanding and capturing the injected water movement including vertical conformance. It includes the latest seismic interpretation, a revamped reservoir rock typing model (Al Ameri 2011), updated well descriptions, and a detailed mapping of the high permeability streaks and dolomitic zones (cf. Yamamoto 2011).
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