ORKA: Limits

ORKA: Limits™ is a reservoir engineering tool for shale gas and unconventional reservoirs. Limits uses readily available and routinely collected pressure and rate data to determine feasible ranges of physical reservoir and completion parameters in order to estimate the uncertainty in the future performance of the well. All well data is stored in Object Reservoir’s Knowledge Architecture (ORKA) and is fully searchable via a variety of well input parameters. Once the well data are entered, the click of a button generates a comprehensive spread of diagnostic plots, including:

• BHP vs. Time
  • Log (gas rate) vs. time
  • Log (critical unloading rate) vs. time
  • Log (water-gas ratio) vs. time
• Log (Gas Rate) vs. Time
  • Casing-head pressure vs. time
  • Tubing-head pressure vs. time
  • Choke size vs. time
• Inverse Productivity Index vs. Time
• Inverse Productivity Index vs. Superposition Time function
• Log (gas rate) vs. Cumulative Production (linear)

These plots provide enormous value in understanding completion performance, in determining internal linear transient flow regimes, and in allowing for detailed observation of well performance. The normal range of well performance can be very easily ascertained, and any outlying wells (in terms of performance) can be identified for more rigorous study. The parameters illustrated in these plots (Rcomp, Jlt, Jdep, Jlt ex, and Jdep ex) form the physical basis for Limits’ predictive modeling. Once the data are input, the diagnostic plots prepared, the similarity parameters identified, and the physical constraints discovered, the well is ready for probabilistic forecasting.

As a result of the diagnostic plots, Limits generates predictive models and long-term probabilistic forecasts that are completely grounded in the physical behavior of the rock and the rock’s interaction with the completion. Providing forecasts that show upside and downside scenarios based on thousands of model runs, Limits provides a defensible suite of results that can support the booking of reserves and drastically decrease reserve uncertainty. All of the plots and forecasts are stored in the same ORKA hierarchy as the source data.

Limits’ fully validated physics have a proven track record of delivering reliable forecasts. Some of Limits’ key features include:

• Functionality custom built for Shale Gas well analysis, modeling and forecasting
• Using validated physics and actual petrophysical and completion properties derived from well-specific data to generate results
• Data editing, QC and organization functionality
• Constraint analysis to capture the uncertainty of completion and reservoir parameters
• Fully supported Monte Carlo and stochastic forecasting
• Fully supported Pressure Dependent Permeability modeling capability
• Treatment for Wet Gas
• Revolutionary and fully configurable ‘canvas’ User Interface.
• Ability to export parameters from a physics-based forecast as an equivalent decline curve for use in economic analysis packages
• Fully integrated tubing model
• Automated calibration of all stochastic models to production history
• Fully configurable and unobtrusive Data Provenance System, tracking the changes to data and the assumptions so any interpretation can be re-constructed ex post by reservoir engineering managers.

Combined, these features allow the user to diagnose and understand the performance of their Shale Gas wells using a common framework of analysis, based on actual physics and stochastic methodologies which embrace non-uniqueness and uncertainty. Additionally the user will generate accurate, defensible well forecasts on more wells in a fraction of the time compared to more traditional detailed numerical modeling, and with more accuracy than existing decline curve and analytic methods, for use in M&A, and other such activities. Data from hundreds of wells can be cataloged in ORKA to give forecasts that range from single wells to an entire shale play.