--> ABSTRACT: Rock-Fluid Systems Characteristics of Rocky Mountain Laramide Basins: An Example from the Wind River Basin, Wyoming, by Surdam, Ronald C., Zun Sheng Jiao, Yuri Ganshin; #90026 (2004)
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Surdam, Ronald C.1, Zun Sheng Jiao1, Yuri Ganshin1 
(1) Innovative Discovery Technologies, Laramie, WY

ABSTRACT: Rock-Fluid Systems Characteristics of Rocky Mountain Laramide Basins: An Example from the Wind River Basin, Wyoming

An anomalous Previous HitvelocityNext Hit model was constructed for the Wind River Basin (WRB) based on ~2000 mi of 2-D seismic data and 175 sonic logs, for a total of 132,000 Previous HitvelocityNext Hit/depth profiles. Ten cross sections were constructed through the model coincident with known gas fields. In each cross section, an intense, anomalously slow Previous HitvelocityNext Hit domain coincided with the gas-productive rock/fluid interval. The anomalous Previous HitvelocityNext Hit model: 
1. Easily isolates gas-charged rock/fluid systems characterized by anomalously slow velocities and water-rich rock/fluid systems characterized by normal velocities; and 
2. Delineates the regional Previous HitvelocityNext Hit inversion surface, which is characterized by steepening of the Ro/depth gradient, a significant change in connate water composition, and acceleration of the reaction rate of smectite-to-illite diagenesis in mixed-layer clays. 
Gas chimneys are observed as topographic highs on the regional Previous HitvelocityNext Hit inversion surface. Beneath the surface are significant fluid-flow compartments, which have a gas-charge in the fluid Previous HitphaseNext Hit and are isolated from meteoric water recharge. Water-rich domains may occur within regional gas-charged compartments, but are not being recharged from the meteoric water system (i.e., trapped water). 
The WRB is divided into at least two regionally prominent fluid-flow compartments separated by the Previous HitvelocityTop inversion surface: a water-dominated upper compartment likely under strong meteoric water drive and a gas-charged, anomalously pressured lower compartment. Judging from cross sections, numerous gas-charged subcompartments occur within the regional compartment. Their geometries and boundaries are controlled by faults and low-permeability rocks. Commercial gas production results when a reservoir interval characterized by enhanced porosity/permeability intersects one of these gas-charged subcompartments.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.