Evaluation of Lodgepole Waulsortian Mounds using seismic and surface geochemistry

Abstract

The Waulsortian Mounds of the Lodgepole Formation, Williston Basin (Figure 1) present an elusive target that is not easily identified by seismic. Subsurface geology, other than from a regional standpoint, does not aid in the exploration for the prolific mounds. Both 2-D and 3-D seismic have indicated the presence of several mounds but have only led to six new field discoveries. The need for screening out seismic anomalies that are false or do not carry petroleum requires the use of a nonseismic tool. Surface geochemistry, which is not generally pay zone specific, is a tool that can indicate areas of petroleum seepage at the surface and thus focus seismic exploration. However, the use of surface geochemistry and seismic together present a significantly more effective approach to exploration than using the two methods separately for Lodgepole Mounds. Figure 2 represents a seismic section with associated iodine surface geochemistry profile through the southern end of Eland and Versippi Fields, Stark County, North Dakota. There is a closer correlation between the two methods. By elevating various types of seismic anomalies using surface geochemical methods results in the elimination of numerous dry holes and increases success rate. The secondary benefit of using those methods together is the discovery of the other prolific pays found in the basin. Presented here are examples of seismic and surface geochemical surveys used in the Lodgepole Trend in the Williston Basin.