The process of defining the fluid and reservoir properties of a hydrocarbon discovery represents a significant challenge to the industry. The practice of performing a drill stem test (DST) over a significant reservoir interval and attributing the properties of the produced fluid to a single reservoir fluid compartment is problematic. Overlooking the variation in fluid properties that can and do exist in what appears to be a homogeneous reservoir on a typical log analysis can lead to incorrect assumptions about the economic value of the hydrocarbon discovery, the production facilities required to produce the resource and the predicted ultimate recovery.

Recent advances in wireline formation testers have enabled the determination of several fluid properties, including fluid compositions in real time. In addition, mini-DST or Interval Pressure Transient Testing (IPTT) can be carried out at Downhole Fluid Analysis (DFA) stations to provide more representative and accurate mobility/permeability distributions of reservoir layers7 for reservoir characterization.

In this paper, examples illustrate how the use of this technology helped Saudi Aramco effectively address these challenges.

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