Understanding reservoir stacked styles is critical for a successful water injection in a carbonate reservoir. Especially for the giant carbonate reservoirs, different regions with different reservoir architecture stacked patterns developed may be applied to different development options. So reservoir stacked pattern characterization are especially important for the giant carbonate reservoir. This paper propose a systematic method of dynamic characterization on different reservoir stacked pattern, which applied to a giant carbonate reservoir in Middle East.
This paper focuses on a giant carbonate reservoir, which is a Cretaceous carbonate reservoir in Middle East, with conducting waterflooding pilots currently. Thief zones are developed in this reservoir. Four patterns of reservoir architecture stacked style are classified based on geological study. Then the proposed systematic dynamic characterization method are applied, which mainly based on the dynamic data analysis (production data, formation test pressure, production logging test data etc.) and reservoir engineering methods (material balance analysis, well test analysis). Finally, distribution of the four patterns are mapped combined geological and dynamic understanding.
The four patterns have distinctive geological features and dynamic characteristics. For example, pattern A are mostly composed by good quality reservoirs with high production rate for most intervals. Pressure gradient has almost no change from top to bottom, and well test log-log curve shows typical homogeneous reservoir characteristics. And OOIP of pattern A well is large with drainage radius mostly larger than 900m. While from pattern A to pattern D, poor reservoir and barriers increase, which change from massive reservoir to multi-layered reservoir. For pattern D, pressure gradient are separated as zigzag curve, and boundary response is clearly shown in well test log-log curve. Well OOIP and well drainage radius become smaller. After systematic dynamic characterization, reservoir architectures of all wells are calibrated and validated with geological results, and lateral distribution of architecture patterns are mapped.
This paper offers a case study of systematic dynamic characterization of reservoir architectures for carbonate reservoirs. And understanding of reservoir architectures is much valuable for the next development options decision, which means different waterflooding well pattern, well type etc. are applied to different reservoir architectures. It also provides a methodology and reference case for engineers and geologists to investigate on other similar fields.