A Technical and Economic Study of Completion Techniques in Five Emerging US Gas Shales: A Woodford Shale Example

Abstract

With the increased demand for energy and the declining conventional hydrocarbons worldwide, energy companies are turning to unconventional resources such as shale gas. With more than 2,000 Tcf of gas in place indentified in just 5 shale gas plays in the United States, shale-gas formations are now the number one targets for exploration drilling. Furthermore, there are still many more major shale-gas plays and basins waiting to be explored, evaluated, and developed. Because of the extremely low permeability of most shale formations, it is essential to select the appropriate completion techniques for shale-gas reservoirs. There are very few papers in the petroleum literature that provide a logical method to select completion techniques for given shale-gas-reservoir conditions. There are papers discussing successful completion techniques that seem to work for a specific shale. We have used many of these SPE papers to help define "best practices" in completing shale-gas reservoirs. We then developed logic to determine the best practice in completing shale-gas reservoirs as a function of reservoir conditions. In this paper, we will specifically cover the logic we have developed for choosing completion techniques in shale-gas reservoirs.First, we performed a literature review on the five basins as well as on all shale-gas plays in the US to determine the best practices in shale-gas completion techniques in fluctuating price environments and identify key geologic parameters that affect overall well performance. From our literature review, we identified seven pertinent geologic parameters that influence shale-gas completion practices. Next, we identified different completion trends in the industry for different geologic settings. Subsequently, we generated an economic model and performed sensitivity analysis to determine optimal completions for each gas-shale basin. On the basis of these economic models, we developed decision flow charts to select completion techniques. Finally, we programmed the flow chart, and we call this program Shale Gas Advisor. This program can be used to determine optimum completion best practices not only for the five gas-shale basins discussed, but also for gas-shale plays that have similar geologic attributes. We validated the program with published case histories in the SPE literature.

Economic impact analysis of natural gas development and the policy implications

“…In addition, longer drilling laterals were made possible along with the multi stage stimulation (Halliburton, 2008). (Agarawal et al, 2012;Cardott, 2006;Curtis, 2002;Hexion, 2009;Kulkarni, 2011;Mckeon, 2011;Patterson, 2012;Rajtar, 2010;Schulz and Horsfield, 2010;USDOE, 2009) …”

Inventory of Shale Formations in the US, Including Geologic, Geochemical, Hydrological, Mechanical, and Thermal Characteristics

“…Agrawal (2009) describes the depositional environment, mineralogy and TOC of the Woodford. GIS data for the Woodford Shale within the Anadarko and Arkoma Basins were generated from Amsden (1975; (Figure 2-13).…”

“…Hammes et al (2011) presented a detailed description of the regional geology and stratigraphy of the Upper Jurassic Haynesville Shale, including isopach and structure maps of this important shale gas play unit; these maps were digitized to generate GIS data to create depth and isopach maps for this unit (Figure 2-14). Agrawal (2009) describes the depositional environment, mineralogy and TOC of the Haynesville. Surles (1987) constructed isopach maps for the entire Eagle Ford shale and its members, as well as compiled information on the amount of sand and organic matter.…”

Economic appraisal of shale gas resources, an example from the Horn River shale gas play, Canada

“…In recent years since the start of the shale gas boom, methods and procedures of economic feasibility evaluation of shale gas development have been proposed and examples of economic appraisals of North American shale plays are publically available in literature as well as from industry reports. Agrawal (2009) conducted an economic analysis on five emerging shale gas plays in the United States for two types of completions-vertical and horizontal to examine which completion method is the best under different economic environments. A discounted cash flow (DCF) model was used to generate economic yardsticks, such as net present value (NPV), internal rate of return (IRR) and payout time for comparing the economic outcomes in those five emerging shale plays.…”