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Identifying Pore Structure and Clay Content from Seismic Data within an Argillaceous Sandstone Reservoir

Robert Schelstrate
Department of Geology and Geophysics, Texas A&M University

Sandstone facies are ideal reservoirs for the accumulation of hydrocarbons in conventional exploration due to high porosity and permeability. Interbedded sandstone and shale, however, often occur in a depositional sequence. The shale potentially becomes a limiting factor in the quality of the reservoir by creating baffles to fluid flow. Previous studies (Sun, 2004; Adesokan, 2012; Xu, et al., 1995) have developed rock physics models of identifying critical clay content (Vcc) from well log data in a shaly sandstone reservoir. The goal of my study is to correlate this rock physics-based petrophysical parameter with seismic attributes in order to map and predict the location of fluid baffles, which can be a hindrance in the development of hydrocarbons. An area of increased clay content could symbolize a zone within the sandstone reservoir in which fluid flow is not optimal. Seismic data can be used to locate high clay areas in fluvial environments, where meandering channel deposits range from channel fill to proximal and distal levees. This project will begin by calculating the critical clay content by applying the model proposed by Adesokan (2012) to wells logs within the Norne field, offshore Norway. Two methods of synthesizing petrophysical data with seismic data will be applied and compared. First, geostatistical techniques will be used to synthesize petrophysical data with extracted seismic attributes. The seismic attributes used in the geostatistical approach focus on the interface boundary between two rock layers, which cannot accurately account for any changes beneath seismic resolution. The second method, seismic inversion, will use the well log data to build an inverse model of reservoir interval to identify how clay content varies within the reservoir. Geostatistical and inversion methods will generate reservoir models predicting zones of increased clay content within the argillaceous sandstone reservoir.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013