News Release, Kansas Geological Survey, Nov. 7, 2011
LAWRENCE--Using a new, noninvasive mathematical tool, the Kansas Geological Survey based at the University of Kansas has been collecting data on underground rocks in an Ellis County oil and gas field.
The Survey is studying the Arbuckle Group of rocks to determine if it can permanently hold CO2 injected during oil operations or for permanent storage. The project is a subsurface characterization investigation and will not include sequestration of CO2.
Now, along with industry partners Vess Oil Corporation and Murfin Drilling Company of Wichita, the Survey is drilling a horizontal well, spudded November 1, in the Bemis-Shutts field to test how accurately the tool--a three-dimensional, seismic-derived volumetric curvature--can provide images of subsurface linear features, such as faults.
Survey geologists Jason Rush and Lynn Watney are leading the investigation, which is funded by a $1.5 million U.S. Department of Energy (DOE) grant.
In the Bemis-Shutts field, where the Arbuckle is not as deep as it is in southern Kansas, CO2 will likely only be used in oil recovery operations, Rush said.
More than 3,500 feet deep and up to 1,000 feet thick, the Arbuckle is isolated by numerous impermeable layers, or cap rocks, from the much shallower freshwater surface aquifers.
The horizontal well starts out vertical, gradually turns in a horizontal direction and will head through about 2,000 feet of the upper Arbuckle. The borehole will be drilled through an ancient sinkhole below the oil zone.
"The horizontal part of the well is purposely being drilled to intersect faults, fractures, and paleokarst, suggested by volumetric curvature, so that we can evaluate their dimensions, orientation and permeability," said Rush.
Paleokarst--a landscape of ancient caverns and sinkholes formed in limestone and other soluble rocks now buried beneath thousands of feet sediment--sits atop the Arbuckle.
"One question we hope to address is whether ancient karst features coincide with long-lived faults and whether those faults may act as leakage pathways," Rush said.
CO2 sequestration--the containment of CO2 from industrial processes and other sources--is being explored worldwide in an effort to reduce the greenhouse gases released into the atmosphere. CO2 is already used in tertiary oil operations to squeeze out trapped oil that is hard to recover using traditional methods.
Once the well is completed, measurements and images collected from the well will be compared to maps generated by the volumetric curvature tool to confirm the tool's utility.
"If results are promising, we envision using seismic volumetric curvature attributes as a screening tool, whereby we can eliminate locations that have potentially conductive faults," Rush said. "The results will also be used to better understand karst-related reservoir compartmentalization within existing Arbuckle oil fields."