University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 5-2014 Mechanical Stratigraphy of the Mississippian in Osage County, Oklahoma Caleb James Jennings University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/etd Part of the Geology Commons, and the Geophysics and Seismology Commons Recommended Citation Jennings, Caleb James, "Mechanical Stratigraphy of the Mississippian in Osage County, Oklahoma" (2014). Theses and Dissertations. 2347. http://scholarworks.uark.edu/etd/2347 This Thesis is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected], [email protected]. Mechanical Stratigraphy of the Mississippian in Osage County, Oklahoma Mechanical Stratigraphy of the Mississippian in Osage County, Oklahoma A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology by Caleb Jennings University of Arkansas Bachelor of Science in Geology, 2012 May 2014 University of Arkansas This thesis is approved for recommendation to the Graduate Council. ____________________________________ Dr. Christopher Liner Thesis Director ____________________________________ ____________________________________ Dr. Matthew Covington Dr. Adriana Potra Committee Member Committee Member Abstract The Mississippian formation of Oklahoma and Kansas has recently developed as a world class unconventional reservoir with wells producing up to 800 bbl/day. The Mississippian is composed of multiple distinct lithologic zones including limestone, hard chert, and soft tripolitic chert. These zones are difficult to discern with traditional log correlation, but mechanical stratigraphy has the potential to improve previous correlations of the Mississippian. This study uses full wave sonic logs from Osage County, OK to analyze the elastic properties of the Mississippian. Our work computes isotropic elastic parameters in an effort to partition the Mississippian section into units that may be correlated between wells. Raw material for this study consists of P-sonic, S-sonic, and density logs in two wells. From sonic log data we compute metric P- and S-wave velocities, then calculate the two independent isotropic elastic parameters (Lame's constant and shear modulus) at every log depth through the Miss and a short section above and below. Young's modulus, a key parameter related to brittleness and fracability, is shown to vary vertically and laterally in the Mississippian. Through our work to separate the Mississippian into multiple distinguishable units, we may be able to better correlate logs in this area as a guide for oil exploration mapping and completion. Acknowledgements I would like to thank my advisor, Christopher Liner, and my committee members, Matthew Covington and Adriana Potra, for all of their help and guidance on this project. I would also like to give a special thanks to Charles Wickstrom, who donated a portion of the data used in this project from Spyglass Energy. I would also like to thank Maurice Storm of Nemaha Resources and Randy Lawson of Lawco for donating sonic log data to this project. This thesis is a product of the Multiscale Arkansas Unconventionals Project (MArkUP) established in 2012 and directed by Professor Christopher Liner. Table of Contents 1. Introduction………………………………………………………………………………….....1 2. Geologic Setting and Site Information………………………………………………...………2 2.1 Site Background……………………………………………………………………….2 2.2 Geologic Setting…………………………………………………………………….....4 2.3 Stratigraphic Section………………………………………………………………..…5 2.4 Structure…………………………………………………………………….…………9 3. Purpose and Scope……………………………………………………………………..….….14 4. Previous Investigations…………………………………………………………………..…...15 5. Mississippian Section in Osage County, Oklahoma…………………………………….……17 5.1 St. Joe Formation………………………………………………………………….…17 5.2 Boone Formation………………………………………………………….…...…….18 5.2.1 Lower Boone……………………………………………………………….20 5.2.2 Upper Boone…………………………………………...………….……….23 5.2.3 Chat…………………………………………………………………...……26 5.2.4 Tripolite…………………………………………………………………….29 6. Rock Mechanics and Methods…………………………………………………………....…..36 6.1 Raw Data description………………………………………………………………...36 6.2 Converted Quantities……………………………………………………………...…37 6.3 Independent Mechanical Parameters……………………………………………..….39 6.4 Dependent Mechanical Parameters…………………………………………………..41 7. Results and Correlations…………………………………………………………………...…50 7.1 Zone Discriminators for the Mississippian………………………………….…….…50 7.2 Log Overview……………………………………………...………………...50 7.3 Zone Divisions………………………………………………………….…....52 7.4 Density of Tripolite…………………………………………………………………..55 7.5 Zone Correlation……………………………………………………………………..58 7.6 Brittleness Attributes………………………………………………………………...60 7.7 Gamma Comparison…………………………………………………………………63 8. Conclusions………………………………………………………………….………………..65 References………………………………………………………………………………….……66 Appendix………………………………………………………………………………………...69 List of Figures Figure 1: Google Earth map showing the locations of wells in the study area………………...…3 Figure 2: Paleogeographic map showing depositional environment……………………………..5 Figure 3: Stratigraphic columns used for Mississippian outcrop studies………………………...6 Figure 4: Stratigraphic column of the Ozarks developed by MArkUP group……………………7 Figure 5: Stratigraphic column of Osage County, Oklahoma developed by MArkUP group……8 Figure 6: Geologic provinces map of Oklahoma locating the study area……………………….10 Figure 7: Structural cross section A-A’…………………………...………………………….…11 Figure 8: Structural cross section B-B’………………………………………………………….12 Figure 9: Structural cross section D-D’…………………………………………………………13 Figure 10: Chert types seen in Boone Formation outrcrops………………………………….…19 Figure 11: lower Boone seen in outcrop…………………………………………………….…..22 Figure 12: upper Boone seen in outcrop………………………………………………………...25 Figure 13: Mississippian unconformity from the Wild Creek survey……………………….….28 Figure 14: 3D image of the top of the Mississippian from the Wild Creek survey………….….33 Figure 15: Tripolite seen in outcrop…………………………………………………….……….34 Figure 16: Global sea level curves………………………………………………………………35 Figure 17: Converted well log quantities…………………………………………………….….38 Figure 18: Log curves for the two independent parameters, λ and µ…………………………...40 Figure 19: Log curves for dependent parameters……………………………………………….42 Figure 20: Brittleness crossplot defined by Rickman et al. (2008)…….…………………….…44 Figure 21: Brittleness crossplot defined by Goodway et al. (2007)………………….…………46 Figure 22: Brittleness crossplot defined by Sharma (2012)………………….……………….…48 Figure 23: Three brittleness curves defined in literature………………………………….….…49 Figure 24: Mechanically distinct Zones defined through the Mississippian…………………....54 Figure 25: Density comparison of the four wells in the study area………………..……………57 Figure 26: Zone correlation across study area……………………………..……………………59 Figure 27: Goodway et al. (2007) brittleness curve and Poisson’s ratio………………...……...61 Figure 28: Rickman et al. (2008) and Sharma (2012) brittleness curves and Young’s modulus.62 Figure 29: Gamma curve comparison of the four wells in the study area………………………64 1. Introduction The Mississippian section of Osage County, Oklahoma has been a major petroleum producer for over one hundred years. Historically, the largest producing interval has been the highly porous unit in the upper portion of the section, known as the Chat (Rogers, 2001). The term Chat refers to the altered section toward the top of the Mississippian section that can be any variety of chert breccia, regolith facies, or tripolitic chert developed toward the top of this section (Manger, 2014). Other intervals within the Mississippian, informally called the Dense Lime, were known to contain oil; however these intervals consisted of tight limestone and chert with too little porosity to be developed as a conventional reservoir. The last several years have seen a resurgence of interest in the Mississippian play in Osage County, largely due to the advent of horizontal drilling and hydraulic stimulation techniques (Dowdell, 2012). These techniques have facilitated a dramatic increase in production from non-Chat intervals, thus creating a need to better understand the Dense Lime interval of the Mississippian. This reservoir is heterogeneous and difficult to interpret using standard geological techniques. Dipole sonic log data may be useful to discriminate mechanically distinct intervals through a section otherwise difficult to differentiate. Rock mechanics derived from sonic data could be a powerful tool for the description of zones within the Mississippian section. 1 2. Geologic Setting and Site Information 2.1 Site Background Osage County is located on the Cherokee platform in northeastern Oklahoma, a region of subtle structure influenced by the Nemaha uplift to the west and the Ozark uplift to the east (Johnson, 2008). Although Osage County has been the subject of conventional hydrocarbon exploration and production for over one hundred years (Bass, 1940), it has recently seen a resurgence of interest as an unconventional reservoir. This interest is driven by rising oil prices, enabling technologies such as horizontal drilling, hydraulic stimulation, 3D seismic surveys, and dipole sonic logs, all of which can be important when characterizing an unconventional reservoir. The four wells included in