Michael Langeler1, Brian Toelle2, Karen Glaser2
(1) Cross Timbers Oil Company, Fort Worth, TX
(2) Schlumberger - GeoQuest, Houston, TX
ABSTRACT: Complex Structural Mapping Without 3D Seismic Data
In 1998 controlling interest of the Middle Ground Shoal field was obtained from the Shell Oil Company by the Cross Timbers Oil Company of Fort Worth, Texas. This field is located in Alaska's Cook Inlet and is a north-south trending anticline that is structurally complicated by multiple thrust faults as well as vertical and overturned bedding. This complexity has resulted in poor seismic data quality in this area.
Cross Timbers, seeking to boost the field's production, began analysis of the well data in order to plan future development wells. An extensive effort was made to map the steeply dipping to overturned west flank portion of the field. Using existing dipmeter and deviation survey data, true horizontal thicknesses were calculated for the productive intervals and then plotted along the well paths at each formation intercept. These values were then contoured and the result was a "planar" view map that helped identify additional drilling opportunities.
However, even with the extensive mapping visualization of the west flank structure proved difficult. Because a thorough understanding of the field's structure was essential during this well planning phase the construction of a structural framework of the field's productive horizons was undertaken. Since the overturned nature of the beds limited the software tools that could be used a modified seismic interpretation workflow was employed on the well data. The results, when combined with the mapping, ultimately produced a comprehensible picture of the field's western side, decreased the structural uncertainty and allowed for confident well planning.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado