Friday, May 24, 2013

Case Study via SLB: MicroScope Resistivity Niobrara Shale

via http://www.slb.com/resources/case_studies/drilling/microscope_niobrara_shale.aspx


Case Study: MicroScope Resistivity and Imaging Enable Successful Completion in Complex Shale Formation

Real-time high-resolution images accurately identify formation dip, faults, and natural fractures for placement of lateral within Niobrara target zone

Challenge: Maximize wellbore intersection with natural fractures to optimize oil recovery from highly faulted zone in Niobrara shale.
Solution: Use real-time images from MicroScope resistivity- and imaging-while-drilling service to confirm borehole position relative to target formation and identify and characterize natural fractures.
Result: Successfully placed horizontal lateral within predefined target interval and completed well for production.
A MicroScope horizontal borehole image acquired while drilling is shown here with correlated dip data.

Intersect maximum number of natural fractures

An independent operator in the western US planned to drill a horizontal lateral to produce oil from a complex reservoir in the Niobrara shale formation. Prior to drilling the lateral, a complete openhole log, including images from an FMI fullbore formation microimager, was acquired in a vertical well to identify the best horizontal target interval, confirm the presence of natural fractures, and determine the maximum horizontal stress orientation.
This information was used to select the direction the horizontal lateral should be drilled to maximize the number of natural fractures it would intersect and facilitate the development of a complex fracture network during stimulation. To enhance reservoir understanding and optimize oil recovery, the operator needed to correlate and confirm the position of the borehole relative to the target formation while drilling.

Optimize wellbore placement in highly complex reservoir

MicroScope service provided high-resolution electrical borehole images, azimuthal gamma ray measurements, and multidepth formation resistivity measurements in real time. This information, together with mud gas data, was used to constantly update the structural model and determine wellbore trajectory relative to the target interval in the highly faulted reservoir.
When the lateral had been drilled to about three-quarters of its planned length, it crossed a major fault plane with a significant fault throw, which placed the lateral below the target formation within just a few hundred feet of TD. To improve reservoir exposure, the operator decided to drill a sidetrack from the existing lateral.

Improve structural understanding

The improved structural understanding that interpretation of the real-time MicroScope images provided made steering the sidetrack less demanding than steering the original lateral. While drilling the sidetrack, real-time MicroScope images revealed that there was less structural change than there had been in the first half of the lateral. Constant updating of the structural model based on real-time data enabled successful placement within the predefined target interval and well completion.

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