Schlumberger

Technical Paper: Advanced Methods to Design and Interpret Exploration Well Tests: Two Case Studies

Society: SPE
Paper Number: 123555
Presentation Date: 2009
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Abstract

Two drillstem tests (DSTs) from a well in an offshore field in the exploration phase were conducted to identify whether seismic anomalies between the well and a bounding fault act as impediments to flow. Rate deconvolution was used to generate the single-rate system response and consequently to help provide the following benefits: a significant reduction in the ambiguities associated with the interpretations of conventional derivatives of the pressure buildups, and a characterization deeper into the reservoir than that possible with these derivatives.

A new method for DST design uses experimental design to enable systematic calculation of expected success when several scenarios exist for the reservoir. It also provides a way to maximize these chances, given fixed resources such as rig time. The new method may exploit analytic models and finite-difference simulation (coupled with geological modeling packages) to predict DST behavior.

Case histories illustrate why pressure and rate deconvolution shows promise to improve pressure transient interpretation. One case study demonstrates a new method of job planning based on experimental design followed by Monte Carlo simulation, suitable when little is known about a field that is in an exploration or early appraisal stage. A major challenge in these cases is confidence that the program meets the defined objectives--no matter the reservoir or well completion conditions that are actually encountered.

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