Fractured reservoir detection and evaluation using well test analysis

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 combination). This determination is amore » controversial issue, especially during exploration where the evaluation commonly is based only on logs, outcrops, cores, and information from drilling.« less