Fractured Reservoir Discrete Feature Network Technologies

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Marathon Oil Company will collect reservoir performance data related to implementation of the TAGS process, and will provide this data in formats appropriate for incorporation into the WWW-accessible database. This data will be include hydraulic response data, in addition to borehole data such as electronic log (FMS/FMI) output for definition of the fracture network.

Task 4.1.1 Fracture Image Data Acquisition

In this task, Marathon will collect and process fracture image data such as FMS/FMI logs for the Yates field study site, and will provide this data in electronic formats appropriate for incorporation to the WWW server.

Task 4.1.2 Well Testing Data Acquisition

In this task, Marathon will collect and process well test and hydraulic responses related to the TAGS process in the fractured reservoir Yates field study site, and will provide this data in electronic formats appropriate for incorporation to the WWW server.

Discussion:

Marathon Oil Company will conduct a preliminary evaluation of the TAGS process beginning in 1995. Available fracture imaging tools will be applied as appropriate in available vertical and horizontal wells. Improved methods of obtaining oriented fracture image data from gas-filled wellbores will be explored. These methods may be transferred from shallow/groundwater technology with modification to meet both petroleum reservoir and data analysis requirements. This data will be made available along with more typical additional electronic log (FMS/FMI) output for definition of the fracture network.

Wells have been and will be tested at varying drawdown to improve quantification of fractured reservoir fluid coning behavior. Performance of vertical wells completed in a single “branch” of a fracture network will be contrasted to that of horizontal wells completed in varying numbers of fracture network “branches” as a function of placement and orientation. Completion design optimization for fracture oil withdrawal from a vertically managed unconfined oil column is critically dependent on three-dimensional fracture network flow behavior.

Close observation of field fractured reservoir performance is critical to recognize the rapid response potential of fracture networks. Static observation wells are required to provide continuous surface readout pressures and routine measurements of fracture fluid contact movement in the dynamic producing fractured reservoir. Available historic pressure and contact data will be updated with continuing refined observation of the project area. This electronic database also provides daily production and injection (water and gas) data to record system response to planned or operationally initiated charges (disruptions). The more typical weekly or monthly data gathering in oil fields may not resolve the rapid reaction of the fracture network.

The project area evaluation will benefit from both injection surveys obtained on gas and water injectors, and productivity testing of withdrawal completions for analysis of vertical variation in the fracture network. The ability to gather input for evaluation of fluid contacts in the fracture network provides an opportunity to define “true” three-dimensional fracture network contrast. Sites having only a thin fractured formation or wells completed within a narrow elevation band provide two-dimensional data for evaluation of a three-dimensional problem.