Practical DST Interpretation Seminar
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Practical Drillstem Test (DST) Interpretation Seminar for Engineers & Geologists

Course Outline

Equipment Fundamentals

Basic components in the testing assembly; auxiliary tools and functions. (ie. what is their function, not a lengthy description).

Pre-Test Planning

Use of bottom hole chokes; water and nitrogen cushions; test times; rate stabilization; selection of pressure gauges; design criteria for safety; security; and precision.

Basic Pressure Chart Interpretation

A major portion of the course consists of qualitative inspection of charts (non numerical).

Information Covered

  • How to recognize high or low permeability from the shape of flow and shut in curves.

  • How to diagnose obvious skin damage from the charts.

  • How to recognize depletion of a limited volume reservoir.

  • Use of multiple shut in tests to differentiate depletion from "supercharge".

  • How to recognize mechanical problems (eg. tool plugging, packer leaks, "skidding to bottom on till", etc.).

  • How to recognize pressure gauge and clock malfunctions.

  • How to extract information from misruns.

Quantitative Reservoir Analysis

Horner build-up plots: determining static pressure transmissibility, permeability, skin effect, radius of investigation, stabilized oil or gas rates; AOF and productivity index; DST type curve analysis.

Reservoir Geometry

Use of square root and log/log plots to identify elongate reservoirs, presence of fractures or distance to boundaries; identifying dual permeability systems.

Closed Chamber DSTs

The principles of the method and simple computations used at interpretation will be explained (with field examples) to illustrate the following topics:

  • Use of this test for very tight gas sands where the "flow rate" would be too small to measure on a conventional test (eg. many DSTs in the 'Deep Basin').

  • How to recognize deep damage from the closed chamber surface pressure data (even when a damage ratio cannot be computed from the downhole data).

  • Test design and conduct for safety in regions of sour gas, geo-pressure, and hydrates (particularly appropriate for high rate offshore wells).

  • Accurate producing gas/oil ratio.

Break for a photo. Red Sea, Egypt, May, 2002

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December 2009
© 2009 Hugh W. Reid & Associates Ltd.