Technologies Help Enhance Production From Gas Wells, Storage

(Tech Connections Column, July 2002, American Oil and Gas Reporter)

Whether in exploration and production or gas storage operations, deliverability is all-important in the natural gas arena. Myriad approaches can be employed to enhance deliverability. The following examples, pulled from PTTC workshops, illustrate the diversity of approaches.

A two-day workshop cosponsored by the Oklahoma Geological Survey and PTTC focused on finding and producing Cherokee reservoirs in the southern Mid-Continent. Hidden among many geological gems were two presentations outlining contributions from improved stimulation techniques.

Les Broker, Broker & Capucille, described how improved reservoir understanding and binary foam technologies led to profitable Prue Sandstone wells in the Robberson Ranch Field in Grady County, Ok. There, 1970 vintage wells encountered good pay, but production results using then-accepted hydraulic fracturing technology were poor, so development stopped. An identified reservoir sat there for nearly 30 years. Only recently, recognizing the potential of newer binary foam technologies that keep water off the formation, was another well drilled. Favorable results have led to five new wells. Newer stimulation technologies, combined with improved understanding of reservoir geology, have turned this prospect around. There are other gems similar to this hidden across the patch.

In another presentation, Bob Shelley, Halliburton Energy Services, described how integrated modeling using neural network technology redefined completion/stimulation objectives for a Granite Wash field in the Texas Panhandle. Subsequent field treatments confirmed the validity of changes to completion/stimulation design justified by a neural network model. In fact, average well production was doubled using a less expensive completion. Earlier analysis using conventional evaluation and optimization methods had failed to see well potential. According to Shelley, this is a high-level approach to modeling the reservoir and well completions. This method uses reservoir, geology and completion/stimulation data to develop a field-specific model.

Within the gas storage realm, deliverability is essential. An Appalachian Region workshop featured presentations about several projects–many of which are funded by the Department of Energy’s Strategic Center for Natural Gas within the National Energy Technology Laboratory–and addressed storage well damage. Early work by DOE and the Gas Research Institute identified eight damage mechanisms within gas storage wells (SPE 38863). Of these, damage from hydrocarbons, organic residues, and production chemicals was one of the major mechanisms. Earlier work by DOE/GRI demonstrated that liquid carbon dioxide hydraulic fracturing could be effective (SPE 51066 and 56728), but cost and reliability concerns limited application.

In a current DOE project, Advanced Resources International is exploring a less expensive, nonfracturing, nonpropped CO2-based treatment. Two field test sites, one with Kinder Morgan in Nebraska and a second with Consumers Energy in Michigan, have been selected. In the two sites, different causes for damage were identified. In the Nebraska site, damage resulted from crude oil, valve grease and minor amounts of compressor oil. In the Michigan site, damage resulted from asphaltene and emulsions. Laboratory work has identified promising approaches for removing damage, and field treatments are being planned.

DOE is also funding work that addresses damage from inorganic precipitates, including a project in Pennsylvania’s Summit Field that explores some innovative technologies. Partners, along with DOE, include Holditch Reservoir Technologies, National Fuel Gas, and Penn State University.

In another project, laboratory work and early field testing show that a sonication tool looks promising for removing inorganic damage (http://www.fossil.energy.gov/techline/tl_sonictool.shtml). One field test has been scheduled for August with Nicor Gas, and discussions with several other operators for a second test site are underway.

Horizontal laterals are another alternative for increasing deliverability. In the Donegal Gas Storage Field in Pennsylvania, Columbia Gas Transmission has been employing various recompletion and stimulation efforts since 1993. These include increasing perforating shot density, high sand concentration fracs, tip screen-out fracs, and extreme overbalanced technology, but needed improvements in skin factor and deliverability were not achieved. Columbia did achieve success using underbalanced coiled-tubing drilling techniques when drilling a horizontal lateral (about 450 feet of horizontal exposure in the formation). Initial testing indicates that the horizontal lateral increased well deliverability by more than 8,000 percent (SPE 72373).

In the natural gas vein, readers are encouraged to attend the Colorado Oil & Gas Association’s Rocky Mountain Natural Gas Strategy Conference, Aug. 5-7 in Denver, plus a preceding half-day DOE workshop organized by DOE’s NETL to present results from DOE projects, on the morning of Aug. 5. More information about these events may be found at www.pttc.org.

Contact Mark Hoffman (mahoffman@mail.wvu.edu) for the notebook on the Appalachian gas storage workshop, or contact Jim Ammer, DOE NETL (jammer@fetc.doe.gov) for information about the DOE-funded gas storage projects. For information about the Cherokee workshop, contact Dan Boyd, OGS, at dtboyd@ou.edu or 405-325-3031. Referenced SPE papers may be ordered through SPE’s Web site, www.spe.org.