PFS Interpretations Ltd. is offering a study investigating Upper Cretaceous faults and fractures that occur beneath the Great Plains of North America. “Many Upper Cretaceous hydrocarbon bearing reservoirs can be interpreted with simple models based upon volcanic eruptions and earthquakes. In this study we present evidence showing how these reservoirs have been affected by these faults and fractures during the Late Cretaceous,” says Dr. Andy St-Onge, who first noticed the faults about 10 years ago in Manitoba but did not understand their significance at that time.
“The faulting can cause reservoir accommodation space; then subsequent faulting can fracture reservoirs and then even change the structural position of oil and gas pools,” says Dr. St-Onge. The size of affected pools can vary from prolific single well oil pools in the Second White Speckled Shale Formation to the large shallow biogenic Milk River Formation and Medicine Hat Formation pools. The most exciting results are large exploration fairways for oil-bearing reservoirs such as the Cardium or Dunvegan Formations in Canada and their equivalents in the United States,” says Dr. St-Onge, “I would commence hydrocarbon exploration in Montana, for example.”
There are other applications for the study as well. The faulting and fracturing might also change the way we think about water movement beneath central North America. Various water flow studies have been unable to account for large underground water flow rates in some areas. “The faulting has a fractal nature to it when it occurs. This results in optimal subsurface flow, much like an optimal freeway design,” says Dr, St-Onge.
“The study price may seem expensive at $250,000, but we have spent almost 8,000 hours on data collection and analysis and model building. The study shows how pervasive faulting beneath the Great Plains area can be used as a model for fault development in the Eagle Ford Formation in Texas and perhaps worldwide. The study also shows a seismogenic cause for the creation of polygonal fault systems. We are using fault patterns to infer paleostress in the subsurface and are currently working on inferring lithologic content based upon fracture pattern characteristics. Every time we look for and find local Upper Cretaceous faulting the seismogenic model can be applied to extend drilling potential beyond the data. This is applied science and exploration for the 21st century in a mature basin,” says Dr. St-Onge.
Dr. St-Onge concludes: “In addition to advancing science, some images simply show surprisingly beautiful mud crack patterns beneath us.”
Figure 1 – Mud crack map at the Manitoba/Saskatchewan border about 100 Km north of the United States. The patterns look like mud cracks in a puddle, except for the 10,000X scale change. The map is a computed gradient (edge detection filter) for the reflection corresponding to the Upper Cretaceous Milk River. The average fault has ~5 m offset at this level.
Andy St-Onge
PFS Interpretations Ltd.
1-403-969-3272
www.greatplainsstudy.com