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Pressure Transient Analysis


Saphir was first developed over twenty-five years ago by two engineers who needed a tool for their own interpretation work. It was fast, interactive and robust and it remains so, but much has changed. Saphir has grown to a dominant position in the Industry with over 2700 commercial licenses used as standard by nearly all the Major IOC’s and NOC’s and other clients across operators, service companies and consultants on all continents.
The Saphir methodology has always been based on the Bourdet derivative as the main diagnostic tool; matching the measured data to the model, taking into account the detailed production history.
The ever-increasing processing power of PCs has enabled KAPPA to aggressively expand the technical capability of Saphir. This has resulted in the development of fast numerical models, that has naturally extended to the rigorous solution of nonlinear problems. Saphir is now available only in the non-linear variant known as Saphir NL. When actively maintained under the current pricelist, Saphir NL also includes the well performance analysis module Amethyste as a free add-on.
In v4.20 a minifrac analysis component was developed and the slug-test option was reintegrated. Substantial improvements in the analytical and numerical models were added to better address unconventional formations. An improved Perrine method addresses multiphase flow and material balance correction has been added to the deconvolution. The Rubis sector now allows the Saphir NL numerical model to start from a dynamic state of a Rubis simulation.
Saphir main window

Data loading and editing
Saphir NL offers a wide variety of loading and editing capabilities in order to arrive at a quality checked and consistent set of rate and pressure data. Although this is not the most riveting of subjects, Saphir NL can load an unlimited number of gauges, rates, pressure and other data in almost any format including ASCII, Excel™, PAS and databases of all kinds via OLEDB & ODBC. Saphir NL has real time links with acquisition systems, data drag-and-drop from other Ecrin modules and Diamant Master, which can identify build-ups and initialize Saphir NL on a single click. Multi-layer rates may also be imported from Emeraude.
Data QA/QC and datum correction
Saphir NL offers a comprehensive range of interactive QA/QC tools including trends, tidal correction, gradient analysis and the possibility to compare various gauges to detect sensor drifts and wellbore effects.
Saphir NL can define or import VLP’s and well intake models, either from Amethyste or standard file import. VLP’s are used in conjunction with analytical and numerical models to simulate the pressure at gauge depth or at surface. Alternatively they can be used to correct pressure data a priori to reservoir depth.
Test design
All analytical and numerical models may be used to generate a virtual gauge on which a complete analysis may be simulated. This can take into account gauge resolution, accuracy and potential drift in order to select the appropriate tools or to check if the test objectives can be achieved in practice.
Extracting ΔP and deconvolution
One or several periods of interest, generally shutins, for one or several gauges may be extracted and presented on a semi-log and loglog plot, the latter integrating the Bourdet derivative.
Deconvolution can be used to combine several successive shut-ins into a longer ‘virtual production’. Available methods are (1) von Schroeter et al, (2) Levitan, (3) Houzé et al and (4) a hybrid combination. Saphir NL v4.20 now integrates the Levitan material balance correction.
Specialized plots
Additional specialized analysis plots can be created with options tailored to specific flow regimes. These include very short-term tests or FasTestTM for perforation inflow testing and predefined types such as MDH, Horner, square root and tandem root.
Analytical models
Saphir NL offers a comprehensive built-in analytical catalog combining built-in well, reservoir and boundary models, complemented by external models (see Technical references). Interactive ‘pick options’ are offered for most parameters for a first estimate by selecting a characteristic feature of the model on the Bourdet derivative. There is the option to use the AI package ‘KIWI’ as a guide. Additional capabilities include rate dependent skin, changing wellbore storage, interference from other wells, gas material balance correction, well model changing in time, horizontal and vertical anisotropy.
Numerical models
Numerical models are used for geometries beyond the scope of analytical models. This is predominantly 2D but with 3D refinement where needed. The most complex numerical model to date solves the problem of fractured horizontal wells.
These numerical models also address nonlinearity. Pseudopressures are replaced by the exact diffusion equations for real gas, non-Darcy flow, pressure related physical properties, multiphase flow, water and gas injectors, water drives, and more recently desorption models for shale gas and CBM.
Use of Rubis sectors
A sector of a Rubis full field 3D reservoir model can be imported and run directly in Saphir for a given time range. In v4.20 the starting point is the dynamic state of the simulation at the extraction time. This enables Saphir NL to simulate 3D / 3-phase flow with gravity and in complete coherence with the reservoir model.
Multilayer analysis
An unlimited number of commingled layers that have individual initial pressures can be modeled analytically or numerically. Connected layers can be modeled numerically. Analytical models can superpose internal or external single layer models. Stabilized or transient rates can be loaded and associated with any combination of contributing layers. Rates may be loaded directly from Emeraude analyses. Optimization is performed on both pressure and layer rates.
Optimization and sensitivity analysis
Nonlinear regression is used to optimize the model parameters. This may be automatic or user controlled from a list of variable parameters, acceptable range, and weighting of the data. Optimization may be performed on the extracted period(s) or on the whole production history. Confidence intervals may be displayed. Sensitivity analysis may be performed by running the same model for different parameters.
AOF and IPR analyses are available for vertical, horizontal and fractured wells. Test sequences may be flow after flow, isochronal or modified isochronal, with or without an extended stabilized flow. Transient IPRs are also available. Shape factor and average pressure can be calculated for closed and constant pressure systems. IPR facilities are shared with Amethyste and can be transferred between these modules on a single drag-and-drop.
Minifrac analysis (new in v4.20)
A consistent workflow combines the G-function plot with derivatives to define the leakoff behavior and the closure pressure. It is complemented by square root and after closure analysis plots.
Slug and Pulse
A welcome return after a long break, this was recently restored in v4.20. The processing allows a modified version of the Ramey function to match the slug pressure response of a DST with Bourdet derivative type-curves. This method can also solve for instantaneous production with wellbore storage.
Formation tests
This temporary, free Saphir NL component will be removed in Generation 5 when a dedicated module will be commercially available. This option enables the interpretation of any number of probes, active and interference, to discriminate vertical permeability. Models for packer-probe and probe-probe interference are included with the latter considering storage and skin. An inbuilt preprocessor handles LAS format files and calculates rates from pump volumes.
Reporting and exporting
Saphir has an extensive range of comparison, reporting, exporting and printing capabilities. The free and unprotected Saphir Reader allows files to be read, printed and exported without the requirement for an active license. A ‘slide presentation format’ is available to use Saphir ‘live’ on a LCD projector or to create PowerPoint™ slides.
Edit rates dialog


Deconvolution of two consistent build-ups (von Schroeter et al)

Deconvolution of two consistent build-ups (von Schroeter et al)

Deconvolution of three inconsistent build-ups (Houzé et al)

Classical Horner plot

2-Porosity PSS - Picking the transition

Interpretation using a numerical model

Rubis sectors running in Saphir


Formation testers: Analysis and rates calculation from volumes

Formation testers: Analysis and rates calculation from volumes