Reservoir Characterization and Exploration Assessment of Tight Gas Sands related to Unconventional Concepts. Queen City Formation, Burgos Basin, Mexico

D'Alessio, Silvano; Porras, Mario A.; Arikuma, Tsuyoshi

The middle Eocene, Queen City Formation in the Burgos Basin northeast Mexico, is composed of unconventional reservoirs with low permeability and complex lithology. These tight gas sandstones are related to wave influenced sand bar deposits in a growth faulted system where the main reservoirs are associated to structural-stratigraphic traps controlled by major listric faults. Hydraulic fracturing is required to get commercial gas rates.

The aim of this study is to use well and seismic data to develop an integrated reservoir characterization model and re-explore mature fields based on unconventional concepts (independent of trap), assessing new reserves and resources down dip in the structure close to growth faults where facies, rock quality and thickness improve.

The methodology integrates: (1) The geological model based on wells and regional information, identifying main sand bodies related to growth faults. (2) A multi-mineral petrophysical model and rock types related to Winland cross-plot analysis calibrated with the production performance. (3) The rock physics analysis, geobodies and attributes, generated cross-plotting P Impedance - S Impedance as part of the elastic inversion AVO-AVA, searching for sweet spots related to rock and fluid responses. (4) An AVO analysis with fluid substitution in the position of down dip sweet spots anomalies coming from the simultaneous inversion, reducing uncertainty about high water saturation. (5) Probabilistic evaluation of resources and risk analysis.

The developed analysis has been applied in a real case study related to Queen City Formation sand in two fields where the link between the rock types coming from the Winland analysis and the multivolume attributes coming from the simultaneous inversion, helped to discover and appraise new volumes of reserves independent for the trap.

The contribution of the presented study is to provide a methodology of characterization and re-exploration of tight gas sands reservoirs of complex lithology based on unconventional concepts.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013