A new workflow for petrophysical and texturalevaluation of carbonate reservoirs

摘要

Several researchers have noted the association betweenrock texture and petrophysical properties in carbonates.Therefore accurate petrophysical evaluation requiresthe integration of texture-sensitive logs such as nuclearmagnetic resonance, borehole images, full waveformacoustics, and dielectrics. Lithology and porosity evaluationin the presence of anhydrite or other heavy mineralsrequires the use of neutron capture spectroscopy logs.A comprehensive and accurate petrophysical evaluationof carbonates requires an easy-to-implement workflowto enable rapid and reliable integration of the data fromthis large suite of logs.We describe an interpretation methodology and workflowthat facilitates the integration of logging measurementsessential to accurate carbonate formation evaluation.The workflow is the result of decades of researchinto carbonate petrophysics. The paper shows that themethod provides a rapid, robust, and comprehensive petrophysicaldescription including evaluation of lithology,porosity, tar volumes, pore geometry, permeability, petrophysicalrock types, fluid saturations, relative permeabilities,and primary drainage capillary pressure curves.Examples are presented from major Middle East carbonatereservoirs. We also present a software implementationthat leverages the methodology through an intuitiveand user-friendly workflow.The method has been applied on several wells in theMiddle East within a few hours of the receipt of log dataat the processing center. On a couple of the wells, theresults were available before the tools had been pulledout of the well, permitting decisions on subsequent dataacquisition and on the completion of the well.