PanSystem® Software Technology Overview
Permanent Downhole Gauge Data –
From PanQL™ Software to In-Depth Analysis
The PanQL module is a subset of PanSystem software that has been implemented in Weatherford’s reservoir monitoring system (RMS) and data acquisition unit. The PanQL application will perform an automatic transient analysis quick-look on unscheduled buildups from wellhead or downhole gauge data and will e-mail the results to the reservoir engineer.
PanQL log-log plot: radial flow line and flow regime are fitted automatically to derive k and S. P* is obtained from a Horner plot.
The entire process is automated so that no user interaction is required and no valid buildup, no matter how short, is missed.
- The PanQL program is triggered when a shut-in is detected and the pressure change and duration constitutes a valid data set for interpretation. This is determined by a smart acquisition routine based on defined parameters.
- The following information is obtained from the quick-look analysis:
- k: the effective permeability of the formation
- S: skin factor: the near-wellbore damage or improvement
- p*: the extrapolated formation static pressure (from the Horner plot)
- A synopsis of the PanQL results is then sent to the reservoir engineer via e-mail.
- If the reservoir engineer wishes to further investigate the quick-look, he or she may log in to the system via a web interface, look at the plots and results, and determine whether or not to download raw data or a wavelet reduced data set for in-depth investigation.
- As successive test results are accumulated in the database, these parameters can be graphed against time to reveal trends.
A wide range of reservoir and boundary models, diagnostic plots, line-fit options, type-curves and simulation are available in PanSystem software should a more rigorous analysis be required.
Permanent Downhole Gauge Data – Long-term Data Analysis
Deconvolution module, showing raw data, a sequence of flowing and shut-in periods (upper left); the deconvolved constant rate derivative (right); flowrates before and after adjustment, an optional part of the deconvolution process (lower left).
PanSystem software can be used to analyze an entire permanent downhole gauge record or sections of it rather than just individual buildups. This takes advantage of the huge radius of investigation implicit in any long-term pressure record at a constant rate (ideally) or at different rates interspersed with shut-ins, as is more usually the case to identify remote boundaries, closure, drainage area, pore volume, etc.
Three techniques are available in the pressure decline analysis (PDA) module of PanSystem software.
- Deconvolution: The deconvolution module processes any multi-rate test sequence including flowing periods and shut-ins and, without any prior assumptions regarding models, presents the data in the form of a constant rate drawdown response, from which it is more straightforward to extract the underlying reservoir and boundary models. The module also has the option to minimize errors in flowrate measurements by making adjustments.
- Agarwal-Gardner type-curves: These type-curves are intended primarily for assessment of drainage area and pore volume in semi-steady state systems, but also cover the early transient period.
- Equivalent constant rate (ECR) method: Primarily for semi-steady state analysis, this is a relatively simplistic process which, like deconvolution, converts the data to an equivalent constant rate drawdown.
The powerful wavelet-based advanced data conditioning module has been implemented in the dataprep section to facilitate reduction and denoising of large data sets and to detect rate change events automatically.
The Power of Numerical Simulation
The use of a numerical simulator enables the well test analyst to reach beyond the limits of analytical simulation in terms of complexity of reservoir structure and completion design.
- True 3-dimensional well test simulator
- Complex boundary geometries, irregular shapes
- Multiple layers, multiple completions
- Heterogeneities (rock and fluid)
- Pressure vs. time at any point in the reservoir
The fault structure encountered by this fall-off test could not be modeled analytically in its entirety. The numerical model, which was based on the fault map and created in the PanMesh module, delivered a good pressure and derivative match, confirming the correctness of the map.
The PanMesh™ module is fully integrated into PanSystem software. It fulfills the same basic simulation objectives as the analytical quick match and advanced simulators available in the PanSystem application in terms of model validation and test design, and occupies a similar place in the workflow, but has a far greater modeling capability.
PanMesh’s color visualization facility offers a deeper understanding of the nature of the transient response by tracking the pressure transient as it propagates through the reservoir. This enables the analyst to see how changes in the model structure correlate with changes in the pressure derivative.
Wireline Formation Testing
Pre-test data from a wireline formation tester with probe. PanSystem software has models to interpret the active and interference signals from a dual or packer-probe combination.
The PanSystem application will import wireline formation tester data in conventional LAS format and in Weatherford’s DPK format. Automatic identification of flow periods based on piston movement makes for rapid data preparation.
Models have been implemented for the analysis of probe and dual-packer configurations used for pre-test, pump-out, and mini-DST tests. In addition, active and interference signals from a dual- or packer-probe combination can be processed simultaneously to optimize results.