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Interest is growing in drilling the Austin Chalk formation, with oil and gas companies hopeful that applying the latest unconventional resource development technologies can open a new chapter of expansion in a historically prolific play that dates to the 1920s. Much of the new drilling is in areas of the Chalk that overlie some of the most active parts of the Eagle Ford Shale play in south Texas. Drillers there are taking advantage of the additional stacked play opportunities that can often be drilled with the same rigs and crews they are using in the Eagle Ford and sometimes in the same well. Some operators may have also drilled in the Chalk during the depths of the industry downturn to hold leases and temporarily defer deeper Eagle Ford wells. The Austin Chalk extends from Mexico across south and east Texas and a large portion of Louisiana to Mississippi.
Abstract The Austin Chalk formation has seen several active development booms over the past 35 years due to new technologies. Recently, a program was undertaken to test multistage fracturing technology in the Giddings Austin Chalk field to determine if sufficient additional reserves could be unlocked to spark another development boom. This paper highlights the challenges encountered during the project from the initial reservoir simulation and well candidate selection through system design and installation and treatment design. The Austin Chalk formation has seen considerable horizontal development across Texas as operators chased areas of concentrated natural fractures. Significant quantities of hydrocarbons are apparently trapped in the tight carbonate matrix between the widely spaced fractures along the proven productive edge of the field. Many of the wells in these areas have poorly drained the Austin Chalk due to limited natural fracturing. Multistage fracturing has the potential to reach the insufficiently drained matrix blocks by isolating portions of formation between the natural fractures. A total of 16 openhole multistage hydraulic fracturing completion systems have been run in the Giddings Austin Chalk field across four different counties in an effort to increase EUR’s from existing wells and to extend the economic boundaries of the formation. Simulation work done at the outset of the project pointed towards economic incremental recoveries from multistage hydraulic fracturing. This work also helped validate initial candidate selection. It was found that openhole multistage systems can be run into the Austin Chalk, but it was learned that due to high formation friction factors, careful design work was necessary to ensure that the completion equipment could be run to the desired depth. Results to date have shown that multistage fracturing can increase recovery from existing wells in poorly fractured areas as well as allow for economic development of previously uneconomic fringe areas.
The Austin Chalk formation holds the potential for a resource development revival if the industry can look at it through "a fresh set of eyes," Tony Maranto, executive vice president and chief operating officer at EnerVest, told the SPE Gulf Coast Section's Business Development Study Group recently. Application of the latest technologies and development methods could "move the needle," he said, in a formation that has produced since the 1920s and has experienced more than one heyday--the last one in the 1990s as horizontal drilling was introduced. Maranto, a 35-year industry veteran, joined EnerVest in August 2016 after more than 20 years with EOG Resources. He stressed that he was giving his own views and not necessarily those of EnerVest, which is the largest producer in the Austin Chalk. "I'm not going to end this talk by telling what's going to happen in the Austin Chalk, but I will talk about what can happen," Maranto said.
Rowe, Harry (Premier Oilfield Laboratories) | Sivil, Evan (University of Texas at Austin) | Hendrix, Chris (University of Texas at Austin) | Narasimhan, Santhosh (Premier Oilfield Laboratories) | Benson, Andy (Premier Oilfield Laboratories) | Morrell, Austin (Premier Oilfield Laboratories) | Torrez, Gerardo (Premier Oilfield Laboratories) | Mainali, Pukar (Premier Oilfield Laboratories)
Abstract Beyond the traditional use of descriptive sedimentology for assigning lithofacies, the added ingredient of chemostratigraphy provides unique supporting evidence for the assignment of facies (chemofacies) and the development of more robust paleoenvironmental and diagenetic interpretations. Chemostratigraphic investigation of several cores from Late Cretaceous Gulf Coast strata reveals chemofacies relationships in what is largely a twocomponent system (carbonate-clay). Micro-Rebound Hammer-Unconfined Compressive Strength (MRH-UCS) estimates, coupled with the chemofacies interpretation, outline predictable associations between facies and mechanical stratigraphy that yield insight toward understanding stratigraphically-controlled changes in rock strength that can be quantified and used as inputs for geomechanical models and completions simulations. This presentation focuses onhighlighting the simple element-mineral linkages, developing an understanding of how mechanical stratigraphy changes as a function of chemofacies and the underlying cyclical drivers of clay-rich and clay-poor facies, and introducing a stratigraphically-constrained model of rock strength behavior for Austin Chalk successions that can be used as partial input for induced fracture simulations. Cored strata from Austin Chalk wells represent a broad range of fine-grained lithologies that were used to develop geochemical and chemostratigraphic records of depositional and diagenetic change. Cores were sampled for major and trace element composition at a 2-inch vertical resolution using a Bruker Tracer XRF spectrometer. Raw x-ray spectra were calibrated using a reference suite that encompasses the range of elemental variability observed in the cores. Output from a hierarchical cluster analysis (HCA) of the elemental results was evaluated in terms of a partition index table (PIT), which was subsequently used to define relative elemental enrichments and assign characteristic chemofacies names. Samples representing the range of chemofacies assignments were analyzed for estimates of rock strength using a micro-rebound hammer, defining a general linkage between chemical and mechanical properties of the Austin Chalk.