Schlumberger

Technical Paper: Heavy Oil Sampling with Wireline Formation Testers - A Global Perspective

Society: Other
Paper Number: 13917
Presentation Date: 2009
 

Abstract

Although samples of heavy crude can be acquired with production tests, in many reservoirs operators prefer to use wireline formation testers (WFTs). Heavy oils present significant challenges for these tools: Their high viscosity results in high drawdowns during flow. Their location is typically in shallow, unconsolidated reservoirs where drawdowns can lead to sandface failure. They can combine with water to form emulsions that make analysis difficult and can degrade the sample quality.

Discussion elements are drawn from global experience in successful WFT sampling. First, prejob modeling predicts the drawdowns and flow rates. This information then defines the toolstring. Use of the appropriate hydraulic pump and displacement unit provides control over drawdown. Optimal probe and packer configurations give more control over sandface drawdown. Topics include the emulsions that can affect downhole fluid analysis.

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