--> ABSTRACT: Fractured Reservoir Detection and Evaluation Using Well Test Analysis, by Giovanni Da Prat; #91030 (2010)

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Fractured Reservoir Detection and Evaluation Using Well Test Analysis

Giovanni Da Prat

Interpretation models used in well test analysis for fractured reservoir identification and evaluation are based on the fluid flow behavior of heterogeneous reservoirs. Conventional techniques for fracture detection include use of well logs, seismic surveys, cores, and petrophysics.

The main objective of this study was the identification of fissured formations through the analysis and interpretation of data coming from well tests (e.g., drill-stem, wireline and production tests; buildup, interference, pressure, and flow-rate measurements; etc).

A geological model has been prepared for a fractured western Venezuelan reservoir where the analysis of pressure and production data confirms the existence of natural fractures. One important conclusion derived from this study is that the identification and evaluation obtained from well test analysis interpretation corresponds to the geological setting associated with the drainage volume wherein the wells under study are completed. The reservoir description obtained can be added to the geological model of the zone; particularly useful are those where there is no core or drilling evidence of fissures probably because the well is complete in the matrix. One important aspect when dealing with these type of reservoirs is the location of reserves (in the fissures, the matrix, or a combinat on). This determination is a controversial issue, especially during exploration where the evaluation commonly is based only on logs, outcrops, cores, and information from drilling.

Using the well test analysis methods may make it possible to infer if a reservoir is matrix or fissure dominated. Another important conclusion is the determination of fracture trends. These trends can be inferred from interpreting data coming from interference tests. Also, the presence of formation discontinuities such as faults can be verified.

An integrated effort coming from geology, geophysics, production, and reservoir engineering is vital when planning for field development and oil recovery optimization.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.