Datapages, Inc.Print this page

Results of Recent Drilling at Vernon Field, Isabella County, MI: A Geologic Model for the Top of the Dundee Fm.

J. R. Wood1, T. J. Bornhorst1, S. D. Chitttick1, W. B. Harrison2, D. Barnes2, W. Quinlan3, and E. Taylor4
1Michigan Tech. Univ., Houghton, MI
2Western Michigan Univ., Kalamazoo, MI
3Cronus Energy LLD
4Consultant, Traverse City, MI

A horizontal well with dual laterals was drilled at Vernon Field in the fall of 2000. This well was designed to probe the field for bypassed oil and was sited based on data from previous wells. The initial lateral penetrated the Dundee Formation at –2905 feet subsea and continued approximately due East for 1501 feet, mostly in hard shale (plug?) with no hydrocarbon shows. The second lateral was offset to the Northeast and about 9 feet higher in the section. This lateral encountered good shows and good reservoir rock but efforts to bring it on production failed. The well was plugged and abandonedJanuary 5, 2001.

The main reason for the failure of the well to produce was excessive water production probably due to two main causes: (1) water introduced into the lateral via fractures, and (2) a higher water table than anticipated due to efficient previous production. If fractures were the reason, then serious doubt is cast on the use of laterals to produce bypassed oil from fields of this type. Although the use of a multi-lateral well did allow us to probe the formation for good reservoir rock, the same strategy may have doomed the effort to put the well on production by increasing the chances of cutting water– bearing faults or fractures. On the other hand, a vertical well sited over the shale plug encountered in the first lateral would have likely failed too.

A geologic model was constructed for Vernon Field that takes into account the lithologies encountered in this well. The basic model is that the first well drilled into a large shale plug which is interpreted as either a mud-filled sinkhole originally formed on the surface of karsted Dundee limestone or a shale-filled low on a similarly exposed karstic surface. It appears that the dolomitization was a hydrothermal event following karstification, either subaerially or submarine.

AAPG Search and Discovery Article #90900©2001 AAPG Eastern Section Meeting, Kalamazoo, Michigan