The Effect of Stimulation and Completion Methodologies on Production in Jonah Field
M. Eberhard, M. Mullen, 2004. "The Effect of Stimulation and Completion Methodologies on Production in Jonah Field", Jonah Field: Case Study of a Tight-Gas Fluvial Reservoir, John W. Robinson, Keith W. Shanley
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The past decade has witnessed many changes in hydraulic fracture-stimulation technology and completion operation techniques used in the development of low-permeability reservoirs. Most of these changes have been effective in improving our ability to economically extract hydrocarbons from these unconventional reservoirs. By reviewing the stimulation and completion techniques used in Jonah field over the past decade, a best-practice methodology has emerged of how to treat these low-permeability gas reservoirs from both a hydraulic fracture-stimulation view and a completion practice perspective to identify damage mechanisms and to maximize productivity. The methods discussed here can be applied to low-permeability reservoirs in other basins. However, the techniques discussed here are evolutionary and will one day become dated as new innovations are developed.
The Lance Formation in Jonah field consists of several hundred feet of stacked, lenticular sandstones with reservoir permeability to gas ranging from 1 to 20 μd. The completion of multiple sandstone packages requires 5 – 12 stages of hydraulic fracturing. Spatial sampling and artificial neural networks, guided by an understanding of the reservoir, were used to compare specific stimulation types and completion practices in a well to its immediate offsets. The results suggest the following best practices:
Never shut a well or a fracture stage in for extended periods of time.
Never kill a well or fracture stage with fluid once the hydraulic fracture treatment is cleaned up.
Use composite flowthrough fracture plugs instead of bridge plugs to isolate fracture stages.
Fracture stages should be no longer than 350 ft (110 m).
There should be no more than five entry points per fracture stage.
Completion fluid should be near neutral pH and low gel loading.
The stimulation treatment size should be based on the amount of net pay determined from wire-line logs.
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The discovery of a giant natural gas field within a mature petroleum province is a significant event. Understanding the factors that control such an accumulation is important if the oil and gas industry is to continue to develop natural gas resources. Jonah field, in the Greater Green River basin of southwest Wyoming, is the largest natural gas discovery in the onshore United States in the last 10-15 years with recoverable reserves ranging from 8 to 15 tcf natural gas. Since beginning widespread field development in August 1992, Jonah has produced approximately 1 tcf gas, 10.3 million barrels of oil, and 3.7 million barrels of water. Field production is still increasing with daily production presently at 666 MMCFGPD, 5800 BOPD, and 4000 BWPD from approximately 600 wells. Active drilling continues within the field as operators consider widespread downspacing. By virtue of being a tight-gas field, Jonah is, in many respects, nontraditional. Recent assessments of natural gas potential, for both the U.S. and the world, strongly suggest that most future gas resources will come from low-permeability sandstones in the deeper portions of sedimentary basins, and from fields that will undoubtedly share characteristics with Jonah. The subtle structure, the low-permeability nature of the reservoir, the challenging petrophysics, and the environmental sensitivity surrounding Jonah may foreshadow what explorationists have to look forward to as the demand for natural gas increases, not only in the United States, but throughout the world. This volume brings together previously unpublished material on Jonah field and attempts to integrate all aspects including geology, geophysics, reservoir engineering, drilling and completion, and regulatory affairs. As such, this is a definitive collection that provides a truly integrated perspective of this giant field.