Oil Field Study Reveals Subsurface Geology

Forty-three percent of Kansas oil comes from rocks that are the same age as those that produce oil in Schaben

CONTENTS

Schaben Field Study–page 1

From the Director–page 2

World Wide Web–page 2

New Publications–page 3

Project WET–page 3

A Place To Visit–page 4

In the history of Kansas oil exploration, Ness County’s Schaben field probably doesn’t rate much more than a footnote. Someday it might mean more. With funding from the U.S. Department of Energy, researchers from The University of Kansas (Kansas Geological Survey, KU Energy Research Center, and Tertiary Oil Recovery Project) are working with the field’s operators to find ways of reviving Schaben.

Shaben is important not because it is unusual, but because it is so typical. Discovered in 1963, it has produced about 9.2 million barrels of oil. Over the years, oil production mostly declined while water production went up. That is typical of most Kansas oil fields, and that makes Schaben a good candidate for study. Forty-three percent of Kansas oil comes from rocks that are the same age as those that produce oil in Schaben. Boost production here, and maybe you can boost it lots of places.

Shaben has been heavily drilled over the years, but the first step in this study was to drill three more wells, this time to gather additional, more modern information. The wells brought up complete cores of the oil-producing rocks. Sophisticated suites of geophysical logs were run.

These new data, along with existing information, were used to create computer simulations of the subsurface geology. Those simulations produced maps showing the sweet spots, the best targets for additional drilling. The simulations also helped predict the impact of new wells. “Computer simulations showed what would happen if wells were drilled in specific places,” said Tim Carr, Survey petroleum geologist. “If you’re going to drill dry holes, it’s cheaper to drill them in the office, on the computer.”

Researchers also studied the new cores by using nuclear magnetic resonance (NMR)—a technique from the medical industry that reveals much about the nature of rock’s pore space. Pore space determines the rate that fluids, like oil, move through rock, and thus can be recovered by wells. By producing a clearer picture of rock porosity, NMR helps pinpoint layers that might be particularly productive.

Based on the new information, the field’s operators drilled or re-completed 14 wells in 1996 and 1997; seven more are planned in 1998. Average daily production has increased from about 300 barrels a day in 1995 to around 500 in 1997.

It is much too soon to pass judgment on the cost effectiveness of all this. However, the Schaben study’s ultimate importance may lie in “technology transfer,” or letting people know about the techniques applied to the field. Much of the Schaben field data—production numbers, core photos, gravity and magnetic data, cross sections—are available on the Survey’s home page.

In addition, Survey researchers have taught several courses on reservoir simulation, and more are in the works. “It doesn’t matter much that we’ve done something at Schaben. What’s important is that we’ve done something that can be used on other fields in the state,” said Carr.

Online February 10, 2003

Comments to: lbrosius@kgs.ku.edu

Kansas Geological Survey

URL:http://www.kgs.ku.edu/Publications/GeoRecord/1998/vol4.2/Page1.html