The Application of Geological Concepts for Various Types of High-Permeability Streaks to the Full-Field Simulation Model History Matching of Carbonate Reservoir, Offshore Abu Dhabi

Abstract

Abstract This paper presents a case study of full-field simulation model history matching by applying geological concepts for various types of high-permeability (high-K) streaks. An Upper Jurassic reservoir in "Field-A" is domal shape structure and reservoir fluid is under saturated with bubble point. Field-A has been producing oil from the reservoir for 30 years with total 20 oil producers, by evolved through the secondary recovery stage, such as crestal auto gas injection (non-miscible gas), then shifted to crestal water injection to maintain reservoir pressure. The fluid monitoring results and water-cut/GOR evolution trend indicate complexity and heterogeneity of the reservoir. Two type of high-permeability streaks associated with stromatoporoid lithofacies in the upper part and fault related fractured dolomite in the lower part of reservoir were identified through the reservoir characterization studies. The zones having the high-permeability streaks show higher well-test KH compared to the core plug based matrix KH. Model KH of the zones including high-permeability streaks were conditioned by maps of the excess KH with the following concepts: Stromatoporoid lithofacies: Excess KH map was generated based on the relationship between well-test KH and stromatoporoid lithofacies thickness. Fault related fractured dolomite: Core observation indicates high density of open fractures is detected in dolomite of specific layers in the lower part of reservoir. Excess KH map was generated based on the relationship between excess KH and fracture density distribution estimated by 3D seismic dip attribute (fault location dependent) Through model history matching, stromatoporoid thickness distribution in-between well control points were adjusted to modify excess KH map as one of the major uncertain parameter in the global level matching phase, considering its significant impact on pressure communication between crestal gas/water injectors and flank oil producers at overall area and history period. When it comes to local area (well-by-well level) matching phase, independent fine tuning process of excess KH maps derived from two different high-permeability streaks allowed us to achieve good matching quality for pressure, water-cut and GOR, especially for multi-lateral completion wells where injection water/gas breakthrough was occurred at different timing at each horizontal branch. The permeability modification along with the geological concepts of various high-permeability streaks contributed to achieve reasonable quality of history matching without extreme and un-realistic adjustment of the permeability model.