000			02558nab a2200205 4500
005			20260520000311.0
008			260224s2011 xxu
245	0	0	_aUse of outcrop observations, geostatistical analysis, and flow simulation to investigate structural controls on secondary hydrocarbon migration in the Anacacho Limestone, Uvalde, Texas
260			_a _b _cjul. 2011
270			_a31/08/2011 ; 31/08/2011
300			_a26 p. ; 1181-1206
520			_aTranscripción del resumen del autor. We undertake a multidisciplinary investigation into the distribution of asphalt in the Anacacho Limestone in an effort to decipher the potential roles of fractures and faults on secondary hydrocarbon migration. Field relationships between fractures, faults, and asphalt are evaluated at an asphaltic limestone mine near Uvalde, Texas. Based on their distributions, geometries, and structural relationships, we infer that normal faults provided vertical flow paths through the Anacacho Limestone, whereas strata-bound fractures enhanced lateral permeability. Variograms calculated from 75 subsurface measurements indicate that the asphalt concentration is anisotropically correlated and that the longest correlation length points in the mean strike direction of fractures and faults. A globally positioned laser rangefinder is used to measure faults and stratigraphic contacts within the mine. That data are then combined with lithologic descriptions from surrounding subsurface wells to construct a three-dimensional (3-D) model of the Anacacho Limestone. When an ordinary block-kriging algorithm populates the model with asphalt concentration estimates, the high values align along a trend that connects the two largest normal fault zones at the mine. The 3-D model provides a framework to numerically simulate secondary hydrocarbon migration. We test numerous hydrocarbon migration scenarios by adjusting simulation parameters within physically realistic ranges until producing an oil saturation field that agrees with asphalt concentration estimates. Our best match simulation indicates that oil entered the Anacacho Limestone through normal faults, that regional aquifer flow impacted oil flow, and that fractures increased the horizontal permeability of the formation by an order of magnitude along their strike direction.
581			_a7
773	0		_tAAPG Bulletin _g95
942			_cARTICULO
100	1		_aWilson, Christopher E. _951415
100	1		_aAydin, Atilla _913994
100	1		_aDurlofsky, Louis J. _921214
999			_c185350 _d185350