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Technical Paper: Extending the Limit: Interval Pressure Transient Testing in Low-Permeability Reservoirs in the North Sea

Society: SPE
Paper Number: 124842
Presentation Date: 2009
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Abstract

The low-permeability limit for reservoirs is continually being reduced while the limit for reservoir temperature is increasing. Interval pressure transient testing (IPTT) techniques address these trends by extending the limits for high-quality data acquisition.

The decision on whether to perform IPTT requires an estimate of permeability. This estimate usually comes from either pretesting or other well data. However, these measurements have a shallow depth of investigation and may underestimate the mobility of the reservoir fluids because of formation damage or high-viscosity fluid in the invaded zone. To displace invaded fluids in low-permeability formations can be challenging, usually requiring a high drawdown to pump the mud filtrate and fines from the formation. High-performance packers and pumps are essential in such environments, which require many high differential-pressure cycles.

Three case studies demonstrate IPTT in low-permeability reservoirs in the North Sea. The first involves pretesting with a single probe and dual packer, which indicated a tight formation (no fluid communication between the tool and formation). The second is a tight gas case study in which gas influx was detected. The third illustrates a very low-permeability limestone that was straddled with a dual-packer–standard-probe testing configuration.

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