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Exploitation of the Mississippi Chat Using Horizontal Well Bores in Osage County, OK
Shane Matson1, Ron Haveman2, Dan Jacobs3
1Spyglass Energy Group, LLC, 2Ceja Corporation , 3Ceja Corporation
The Lower Mississippian (Osagean) tripolitic chert, commonly referred to as “Mississippi Chat”, has been a prolific oil and gas producer in northern Oklahoma and south-central Kansas. Though porosity values are high (20-45%), permeability ranges from 10-100 md, making the Mississippi Chat a challenging reservoir to exploit. In the 1950’s explorationists began using seismic surveys with good success in the hunt for “good Chat”. 3D seismic surveys were completed in 1999 on the East Hardy Unit, productive since E. W. Marlin’s oil discovery in the 1920’s. In 2003 Ceja Corporation drilled the first horizontal Mississippi Chat well in Osage County, OK. The prospect location was identified using 3D seismic and located within the unit. Initial production was over 200 BOPD and 450 MCFPD. To date Ceja Corporation and Spyglass Energy have drilled twenty horizontal wells targeting seismically defined and well log confirmed prospects in the Mississippi Chat of Osage County, OK.
Horizontal wells are typically 2000’ in length and drilled using traditional mud motors and tri cone bits. Confidence in geostearing has improved significantly over the past 6 years by using detailed well cutting and gas detector analysis. All wells have been completed open hole with little to no stimulation. Average initial production is 50 BOPD with 200 BWPD. Gas to oil ratios for horizontal wells range from 2:1 – 15:1, making horizontal exploitation for gas production much more favorable than 1.5:1 typical of vertical wells and adds greater positive impact on economics.
The presentation includes data from 20 horizontal Mississippi Chat wells. In August of 2008 these 20 wells had a cumulative production of 750,000 BO and greater than 1 BCFG. The presentation includes information on prospect identification methodology, well bore geometry, past and future drilling and completion techniques, and production history. Sw and So log analysis on three of the wells is included to illustrate problems inherent in Mississippi Chat well log analysis.
AAPG Search and Discover Article #90097 © 2009 Tulsa Geological Society, Tulsa, Oklahoma