Browsing by Subject "Unconventional resources"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Decline curve analysis in unconventional resource plays using logistic growth models(2011-08) Clark, Aaron James; Lake, Larry W.; Patzek, Tadeusz W.Current models used to forecast production in unconventional oil and gas formations are often not producing valid results. When traditional decline curve analysis models are used in shale formations, Arps b-values greater than 1 are commonly obtained, and these values yield infinite cumulative production, which is non-physical.. Additional methods have been developed to prevent the unrealistic values produced, like truncating hyperbolic declines with exponential declines when a minimum production rate is reached. Truncating a hyperbolic decline with an exponential decline solves some of the problems associated with decline curve analysis, but it is not an ideal solution. The exponential decline rate used is arbitrary, and the value picked greatly effects the results of the forecast. A new empirical model has been developed and used as an alternative to traditional decline curve analysis with the Arps equation. The new model is based on the concept of logistic growth models. Logistic growth models were originally developed in the 1830s by Belgian mathematician, Pierre Verhulst, to model population growth. The new logistic model for production forecasting in ultra-tight reservoirs uses the concept of a carrying capacity. The carrying capacity provides the maximum recoverable oil or gas from a single well, and it causes all forecasts produced with this model to be within a reasonable range of known volumetrically available oil. Additionally the carrying capacity causes the production rate forecast to eventually terminate as the cumulative production approaches the carrying capacity. The new model provides a more realistic method for forecasting reserves in unconventional formations than the traditional Arps model. The typical problems encountered when using conventional decline curve analysis are not present when using the logistic model. Predictions of the future are always difficult and often subject to factors such as operating conditions, which can never be predicted. The logistic growth model is well established, robust, and flexible. It provides a method to forecast reserves, which has been shown to accurately trend to existing production data and provide a realistic forecast based on known hydrocarbon volumes.Item Eagle Ford shale : evaluation of companies and well productivity(2016-08) Chavez Urbina, Grecia Alexandra; King, Carey Wayne, 1974-; Lake, Larry W.Unconventional resources, particularly shale reservoirs, are a significant component in oil and gas production in the United States as they represent (as of May 2015) 48 and 58 percent, respectively, of the total oil and gas produced. However, there has been a deceleration on oil and gas production in general because of low market prices. The drastic decline in oil and gas prices that started in 2014 has companies struggling to continue their operations, resulting in negative financial outcomes for 2015 for most companies. The present work examines the financial results of three companies, EOG Resources, Pioneer Natural Resources, and Chesapeake Energy, along with their particular well productivity using the Logistic Growth model to forecast production in one of the most prolific shale plays in the United States, the Eagle Ford. This work also examines the economic feasibility of drilling new wells when oil prices are low using a discounted cash flow model for each company. The financial analysis shows that from the three companies, Pioneer Natural Resources has the best financial results; its high cash-flow-to-debt ratio, and low debt and debt-to-equity ratios make it an attractive company to invest in. In contrast, Chesapeake has the worst results which represents high risk for investors, and EOG has moderate results that still make it a good company to invest in. The discounted cash flow model demonstrate that under the cost assumptions and estimated production used in this work, EOG gets the best results from their wells located in the Eagle Ford with break-even prices bordering the 40 $/bbl compared to the other companies with break-even prices above 87 $/bbl for Pioneer and 89 $/bbl for Chesapeake. From the discounted cash flow model, it can also be concluded that none of the companies in the analysis is expected to gain revenue from drilling new wells if oil prices are under 40 $/bbl, and that companies that are quick to respond to the low prices by reducing their drilling and completion costs can significantly improve their well economics.Item Facies characterization and stratigraphic architecture of organic-rich mudrocks, Upper Cretaceous Eagle Ford Formation, South Texas(2011-08) Harbor, Ryan Lee; Ruppel, Stephen C.; Fisher, W. L. (William Lawrence), 1932-; Steel, Ronald J.The Eagle Ford is a well-known source rock for both sandstone (Woodbine) and carbonate (Austin and Buda) hydrocarbon reservoirs in East and South Texas. Recent discoveries have demonstrated that source rocks, such as the Eagle Ford, are capable of producing significant volumes of gas and oil. At the same time, variations in well producibility indicate that these rocks, like conventional reservoirs, display considerable geological heterogeneity. Yet, only limited research has been published on the subsurface stratigraphy and character of Eagle Ford facies. Understanding the types, controls, and distribution of these heterogeneities requires in-depth rock-based studies. In order to characterize Eagle Ford facies, 27 cores from 13 counties were investigated for rock textures, fabrics, sedimentary structures, and fossil assemblages. These studies were supported by light and electron microscopy as well as analysis of elemental chemistry and mineralogy. Regional subsurface stratigraphic correlations and facies distributions were defined using wireline logs calibrated from core studies. In South Texas, the Eagle Ford Formation was deposited during a second-order transgressive/regressive cycle on the flooded, oxygen-restricted Comanche Shelf. Nine depositional facies consisting predominately of organic-rich, fine-grained (5.0 % TOC) to coarser-grained (3.05 % TOC) fabrics were identified. Facies developed in low-energy environments episodically interrupted by higher-energy, event sedimentation (current winnowing, cohesive and non-cohesive density flows, and turbidity flows). Locally, these rocks show evidence of early diagenetic recrystallization of calcite. Concurrent water anoxia and organic matter preservation persisted locally into later Austin deposition, resulting in formation of a three-fold division of the Cenomanian-Coniacian Eagle Ford Formation. Common facies of lower and upper Eagle Ford members include (1) unlaminated, fissile, clay- and silica-rich, organic-rich mudrocks, (2) laminated, calcareous, organic-rich mudrocks, and (3) laminated, foraminifera- and peloid-rich, organic-rich packstones. The transitional Eagle Ford member consists of highly-cyclic (1) ripple-laminated, organic-rich wackestone (cycle base) and (2) burrowed, organic-lean lime wackestones (cycle top). Transitional Eagle Ford facies developed in oxygen-restricted, basinal depositional environments as distal equivalents to burrowed, foraminiferal lime wackestones of the Austin Formation. Facies complexities in the Eagle Ford stem from complicated and interrelated processes of sediment production and distribution, diagenesis, and water column chemistry. Integrated core studies shed light on both controls of facies formation and their spatial distribution. These findings provide a framework for upscaling the fine-scale, heterogeneous character of shelfal Eagle Ford mudrocks; thus allowing development of predictive models into the distribution of key reservoir properties in the subsurface.