Amethyste is new in Ecrin v4.12. It is a Well Performance Analysis (WPA) module fully integrated within the Ecrin suite. Amethyste spans the divide between datum and the analysis packages Saphir (PTA), Topaze (PA) and Rubis (HM), and provides a natural extension to results obtained from Emeraude (PL). Amethyste brings all the good work we do in modeling the reservoir to where it matters; modeling and predicting production performance at surface or pressure at gauge depth.

So what?

The WPA concept is not new and there are fine vendors who have been developing similar software for years. Indeed the results of those products can be imported into Ecrin using industry standard file formats. But Amethyste is the first module born of the workflow created by the interconnectivity of the Ecrin suite. It was a technical necessity and herein lies the reason for its development. With complete coherence with the rest of the suite, new workflows can be performed incredibly quickly with consistency across the range for wellbore modeling as well as IPR calculations. An IPR defined in Saphir can be drag-dropped in Amethyste. More importantly, a wellbore model defined in Amethyste can be drag-dropped to Saphir, Topaze and Rubis where this model is then run dynamically with complete control. No blind table interpolation as Ecrin runs a full calculation for each pressure guaranteeing accurate and smooth corrections.

Amethyste has its technical roots in WAM, a tried and tested WPA program developed and used by Marathon since 1986. The PVT and flow model libraries come from the unification of the KAPPA Ecrin and WAM codes. This library uniquely combines empirical, mechanistic and drift flux models.

As code is shared with other modules the cost to add Amethyste to Ecrin is very reasonable, unless you are using it before August 2010…until when it is free!

The workflow in Amethyste is similar to other Ecrin modules, with the same logic for loading and manipulating data, and a control panel guiding the user through the default path. The Amethyste browser allows technical objects to be transferred to and from other Ecrin documents. The browser can be used to drag-drop components between analyses or between other Ecrin modules. In particular, a whole VLP object can be dropped in Saphir, Topaze, or Rubis and run from those modules with the possibility of changing any model parameter post-transfer.

After selecting the problem type, the user proceeds with the definition of the Ecrin PVT Black-Oil model, with correlations or tables. The user will define the Well and then the VLP, or will to go straight to the IPR option. If both IPR and VLP have been defined, Amethyste shows an overlay on the WPA plot, which becomes the starting point for subsequent sensitivity studies.

Amethyste distinguishes the wellbore and flowline and they can be treated independently or together. The flow can be defined as annular or tubing. An arbitrary geometry can be defined from an input of step values, or by loading point data such as a caliper survey. Any number of restrictions can be included. A well sketch is available for graphical display using a library of pre-defined completion elements. After the well / flowline have been defined, a well plot is automatically built.

In the VLP option multiple pressure drop models can be selected for comparison over the entire range. A reference is defined that will be used for WPA. The application settings allow the customization of the set used and the default choice. For each model, multipliers can be applied to the hydrostatic and friction pressure drops. These values can be adjusted later to match user data. In the VLP dialog, the user defines the temperature profile, either by two points, a loaded profile or by calculation. When calculated, the temperature uses a segmented model incorporating convection, conduction, and thermal compressibility effects.

The VLP is used to generate various scenarios of traverses (p vs. depth) and VLP plots (p vs. q). For each scenario, user data can be input, manually, from file, or picked from production data. On validation, each scenario is run and the corresponding plot built. The plot content can be customized interactively.

If an IPR study was performed with Saphir (PTA), this can be drag-dropped into Amethyste and the IPR part of the analysis is over. Alternately, test data can be loaded, or drag-dropped, into Amethyste. The IPR option, which is strictly the same as in Saphir, is used to define a single, or composite layer IPR. Multiple models can be selected and compared. A reference is defined that will be used for WPA. For those models using a Skin, the user can input a total Skin or calculate the Skin components using a completion model. User data can be added for comparison with the model(s). An IPR plot is created that can be customized interactively. From this plot, the user may adjust the reference IPR parameters in order to match the data provided.

As soon as a VLP and an IPR have been defined, Amethyste overlays them, and the intersection point gives the solution for a given value of surface conditions.

Amethyste can perform as many sensitivity studies as needed. A given study will correspond to a set of user controlled values for an IPR parameter, a VLP parameter or both. A cross correlation between the resulting rates and the sensitivity parameters can then be displayed.

Amethyste has an extensive range of reporting, exporting and printing capabilities. Lift curves can be generated in Eclipse format for use with third party software. The free and unprotected Amethyste Reader allows files to be read, printed and exported without an active license.