PVT properties of a hydrocarbon reservoir, in addition to estimate oil and gas in place, are required for optimum dynamic reservoir management. In carbonate reservoirs, it is more important as reservoir’s fluid properties usually vary laterally or/and vertically. In this paper, summary results of a study which carried out on the reported PVT properties of reservoir ‘A’ are presented. Reservoir ‘A’ is a real oil carbonate reservoir which suffers from variation of PVT properties. The oil gravity and GOR (gas-oil ratio) in this reservoir are reported to be in the range of 23°–36° API and 300–1400 SCF/STB (Standard Cubic Feet/Stock Tank Barrel), respectively. These wide ranges of PVT properties raised questions about the accuracy and consistency of PVT laboratory test results, FBDST (Full Bore Drill Stem Test) measured data and reservoir characterization, such as effect of seismic recognized faults and the validity of laboratory PVT measurements which conducted on the reservoir fluid samples gathered from adjacent wells in one zone. So, an extensive, systematic study has been conducted on the available fluid data to check the validity of data and find out an acceptable, logical hypothesis about PVT variation across the reservoir, vertically and/or laterally. This study reveals that the reported laboratory measured PVT analysis, oil API gravity and GOR (gas oil ratio) measured in well tests campaign are valid. The PVT variation is dominantly vertical owing to compositional gravity segregation due to relatively high thickness of reservoir, about 300 m (984 ft). It is also distinguished that seismic detected faults (if exist) do not act as barriers at least at geological time.

中文翻译：

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碳酸盐岩储层中PVT性质随深度的变化：一个案例研究

为了估算最佳的动态油藏管理，除了估算到位的油气外，还需要碳氢化合物油藏的PVT特性。在碳酸盐岩油藏中，这一点尤为重要，因为油藏的流体性质通常在侧向或垂直方向变化。本文介绍了对已报告的储层“ A”的PVT特性进行研究的总结结果。储层“ A”是真正的碳酸盐油藏，受PVT属性变化的影响。据报道，该储层中的石油重力和GOR（气油比）分别在23°–36°API和300–1400 SCF / STB（标准立方英尺/储油桶）范围内。PVT的这些广泛范围引发了有关PVT实验室测试结果的准确性和一致性的问题，FBDST（全孔钻杆测试）测量的数据和储层特征，例如地震识别断层的影响以及对从一个区域中相邻井收集的储层流体样本进行的实验室PVT测量的有效性。因此，已经对可用流体数据进行了广泛，系统的研究，以检查数据的有效性，并找到关于整个储层中垂直和/或横向PVT变化的可接受的逻辑假设。这项研究表明，在试井活动中测得的报告实验室测得的PVT分析，石油API重力和GOR（瓦斯油比）是有效的。由于相对较高的储层厚度（约300 m（984英尺）），由于成分重力偏析，PVT变化主要是垂直的。