JP QUANTITATIVE PETROPHYSICAL CHARACTERIZATION OF THE BARNETT SHALE : A case of the study in Denton Co., Fort Worth Basin ConocoPhillips School of Geology & Geophysics M.S. Roderick Perez and Dr. Roger Slatt ABSTRACT The purpose of this study is to identify which facies of the Barnett Shale are most fracturable. The study includes a 100 sq mi three dimensional seismic survey and 164 wells, encompassing an area close to 120,000 sq mi. The area of study was conducted in Denton Co.; Ft. Worth Basin, Texas. In this area the Barnett shale thickens from NNE to SSW. The Barnett Shale reservoir is characterized by low permeability and a variety of depositional facies. Based on gamma ray behavior it can be divided into fourteen gamma ray parasequences (GRP); corresponding to five in the Upper Barnett Shale and nine in the Lower Barnett Shale. In addition, these fourteen GRPs show three characteristic GR log pattern defined as upward decreasing, upward increasing, and upward constant trends. These two main zones are divided by the Forestburg limestone, which acts as a fracture barrier during hydraulic fracturing. The study emphasizes volumetric seismic attributes, such as curvature, coherency, and inversion, to identify and evaluate faults, fracture lineaments, and other features in the Barnett section. The Barnett section within the study has a thickness around 700 ft, which represents 200 ms in seismic time. With an average frequency spectrum of 45 Hz is difficult to resolve internal reflections less than 70 ft thick. Model based inversion was used in order to improve the vertical seismic resolution and to tie in detailed facies core descriptions. The seismic information and vertical well control data played an essential role in the creation of synthetic seismograms to get quality results in the facies model. This work demonstrates that seismic acoustic impedance inversion reveals high heterogeneity in impedance values for the Lower and Upper Barnett section. The underlying hypothesis used in this thesis is that it takes longer for seismic waves to travel through some lithofacies and lesser time in others. Under this criterion, the seismic inversion method was used to analyze the variation in acoustic impedance response among the different gamma ray parasequences. Core studies performed by Singh (2008) show that facies with high calcite content (concretions) contain well defined fractures, indicating that they are fracturable. Thus, we expect that those facies with high calcite content and high impedance might potentially be more fracturable than non-calcite mudstones. The correlation of seismic facies with rock facies is key in this research in order to seismically identify parasequences that could potentially be more fracturable. Finally, this thesis work follows a workflow that allows the identification of facies with high gamma ray and high calcite content (high impedance) in order to identify potentially most fracturable GRPs in the Barnett Shale. Key words: Barnett Shale, seismic inversion, seismic attributes. GEOLOGY OF THE AREA Modified from Pollastro, Modified from Montgomery et al., This research is part of a multidisciplinary project with the goal of integrating different geological and geophysical tools to provide a better understanding of the geology of the Barnett Shale. The Barnett Shale is an organic rich and thermally mature rock deposited during Mississippian time (~340 Ma ago) in the Fort Worth Basin (FWB), TX. It is the primary source rock for oil and gas produced from the Paleozoic reservoirs rocks in the basin. The FWB is a shallow north – south elongated foreland basin, encompassing roughly 15,000 mi in north Texas. It formed during the late Paleozoic Ouachita orogeny (Walper, 1982). FWB is delineated in the east by the Ouachita Thrust Front, north by the Red River Arch, to the north – northeast by the Muenster Arch, west by Bend arch, Eastern shelf and Concho arch, and in the south by the Llano Uplift (Fig ). GEOLOGY OF THE AREA JP SC ASW ST Modified from Singh, Singh, lithofacies related to depositional and diagenetic processes, 14 parasequences characterized by the behavior of the gamma ray log in the Barnett Shale. Vertical Resolution≈70,94 ft AAPG Mid-Continent 2009 / Tulsa, OK 1

QUANTITATIVE PETROPHYSICAL CHARACTERIZATION OF THE BARNETT SHALE : A case of the study in Denton Co., Fort Worth Basin ConocoPhillips School of Geology & Geophysics M.S. Roderick Perez and Dr. Roger Slatt Lithofacies Well DWell CWell BWell A Avg. TOCStd. D. Avg. TOCStd. D. Avg. TOCStd. D. Avg. TOCStd. D. Phosphatic deposit Siliceous non-calcareous mudstone Siliceous calcareous mudstone Calcareous laminae Reworked shelly deposit Micritic/Limy mudstone Silty-shaly (wavy) interlaminated Concretion Dolomitic mudstone GR Phosphatic deposits Calcareous laminae rich deposits Dolomitic mudstone Reworked shelly deposits HYPOTHESIS HIGH GAMMA RAY – LOW FRACTURE POTENTIAL It takes longer for seismic waves to travel through some lithofacies and less time to get through others, depending on their composition. MODEL BASED INVERSION WORKFLOW MODEL BASED RESULTS TRAINING OF NEURAL NETWORK VALIDATION OF NEURAL NETWORK APPLICATION OF NEURAL NETWORK NEURAL NETWORK BASED NVERSION To validate this hypothesis the seismic inversion method was used to analyze the variation of acoustic impedance response among the different gamma ray parasequences. Core studies from Singh show that facies with high calcite content (for example concretions) contain well defined fractures, indicating they are fracturable. Thus, expecting that those facies with high calcite content and high impedance might potentially be more fracturable than the non-calcite mudstone facies. The correlation of seismic facies with rock facies is the key to this research in order to seismically indentify those parasequences that could be more potentially more fracturable. AAPG Mid-Continent 2009 / Tulsa, OK 2 c

QUANTITATIVE PETROPHYSICAL CHARACTERIZATION OF THE BARNETT SHALE : A case of the study in Denton Co., Fort Worth Basin ConocoPhillips School of Geology & Geophysics M.S. Roderick Perez and Dr. Roger Slatt ZoneGR Min GR Max GR MeanGR StD. Marble Falls U. Barnett Lm GRP GRP GRP GRP GRP Forestburg GRP GRP GRP GRP GRP GRP GRP GRP GRP AAPG Mid-Continent 2009 / Tulsa, OK 3 High gamma ray – low fracture potential High gamma ray – high TOC content CONCLUSIONS Gamma ray and acoustic impedance logs are correlated to the gamma ray parasequences identified in the Barnett Shale. Acoustic impedance inversion results for the 3D geological model allow the mapping of lithofacies which contain high calcite content – high impedance. Field trials indicate that these parasequences might potentially be more fracturable for a hydraulic fracture job. Cluster modes Clustering analysis for bed sets from well logs (Wallet and Perez, 2009) ACKNOWLEDGEMENTS I would like to give thanks to Devon Energy Corporation for supporting this research with data and providing funding in the form of my research assistantship. I would also like to thank Schlumberger for the licenses to use Petrel 2008© which was very helpful in completing this research.