Production Analysis has recently evolved from old empirical methods to a modern methodology that shares a lot of analysis and modeling tools with pressure transient analysis. With over 1300 commercial licenses Topaze NL, the Ecrin module dedicated to PA, is used by clients ranging from the Major IOC’s to NOC’s and smaller independents on all continents, frequently as a complement of Saphir NL.

The abundance of data from permanent gauges has meant that users are able to obtain answers that were previously only available from transient tests. This information has the advantage that it is available at no extra cost and with no deferred production. As the long-term production is modeled, the evolution in time of the well productivity may also be quantified. Finally, forecasting is based on a real model as opposed to an empirical function.

Topaze NL unique features include a total compatibility with Saphir NL data and models, an extensive analytical model catalog and a unique numerical capability that allows reliable history matching and forecasting, even in the case of shale gas and CBM produced by fractured horizontal wells. Its multiwell capability allows very fast full-field decline analysis and forecasting. A field production profile generator is integrated in Topaze NL.

In v4.20 Topaze NL integrates additional specialized plots and substantially enhanced analytical and numerical models, especially adapted to the low permeability range of unconventional formations. Topaze NL, when actively maintained under the current pricelist, also includes the well performance analysis module Amethyste.

Topaze can load and edit an unlimited number of gauges, rates, pressure and other data in almost any format including ASCII, Excel™, PAS, DMP2, Merak and databases of all kinds via OLEDB & ODBC. Topaze has real-time links with various acquisition systems, and data drag-drop from other Ecrin modules or from Diamant Master.

When pressures are acquired at surface, or at any point other than the sandface, the well intake option allows either the loading or generation of a well intake response to simulate sandface pressure. When the user extracts the data for analysis, options include the choice of pressure and rate gauge, time range, time sampling, and whether or not to correct pressures to datum which, in v4.12, may be the wellbore model created and copied seamlessly from the Amethyste (WPA) module.

An ever-increasing list of specialized plots is available in Topaze NL:
• Multiple variants of the Arps plot.
• Fetkovich type-curves
• P-Q plots, to discriminate between transient and boundary dominated flow
• Normalized rate cumulative plot
• A variation of the Agarwal-Gardner
• Flowing material balance
• Square root plot (new in v4.20)
• Power law loss ratio plot (new in v4.20)

When pressures are acquired at surface, or at any point other than the sandface, they can be corrected to datum using well intake models created by Topaze NL, imported from third party software or drag-anddropped from Amethyste.

The three main and complementary diagnostics used in Topaze NL are the rate and pressure history match, the loglog plot and the Blasingame plot. The Blasingame plot displays on a loglog scale the instantaneous and average productivity index, with derivative, vs. material balance time. Type-curves are also available. For gas material balance, the time is replaced by the material balance pseudotime. The simulated model can be compared to the data on these three plots.

With a wide range of well, reservoir and boundary models (see technical references) Topaze NL can simulate pressures from rates, rates and cumulative production from pressures, or both. History matching is obtained by nonlinear regression of the model on pressures, rates, cumulative production or any weighted average.

Topaze NL numerical models are used to generate complex geometries beyond the scope of analytical models. This is predominantly 2D but with 3D refinement where needed (see Ecrin). The most complex numerical model to date has been added to solve the problem of fractured horizontal wells.

Numerical models also address nonlinearities, replacing the linear diffusion used in analytical model by the real diffusion equations solving for real gas, non-Darcy flow, pressure related physical properties, multiphase flow, water drives, and desorption based on the Langmuir isotherm, for shale gas (single phase) and coalbed methane (2-phase water-gas).

The multiwell mode of Topaze NL facilitates the analysis of the production of multiple wells. The production data can be loaded simultaneously in formats including DMP2, Merak, or by drag-drop from Diamant. It is then possible to view this data together in a browser, and conduct quick or detailed analysis of all wells or groups of wells. The results are viewed easily as tables or bubble maps as required and then it is a simple step to construct a field profile from any extension of the selected diagnostic, be it a decline curve or a complex model.

The numerical module allows the simulation of multiple well productions, where individual wells can be pressure or rate controlled. Topaze NL permits 2D and 3D visualization of the well drainage areas and their evolution with time. If the simulation deviates from the data and indicates a change in the well productivity index the user may assign individual skin values to different production periods. Nonlinear regression is then applied on all skins, resulting in a relationship between mechanical skin and time.

Without data, or after history matching, a production forecast for any model may be run based on the anticipated producing pressure. Sensitivity to production improvement or decay can be simulated. One can specify a wellhead pressure constraint for the reference well if an intake has been defined.

This tool provides a uniform and standardized approach to obtaining quick production estimates for new fields and incremental recovery studies. Valid for oil, gas and condensate the user can model water or gas drive taking into account all producing and/ or injecting wells. It allows the input of an unlimited number of various well-type profiles and generates a field production profile consistent with the drilling and workover schedule and facility constraints. The profile generator can use a multiwell field profile as a baseline for an incremental study.

Topaze NL has an extensive range of comparison, reporting, exporting and printing capabilities. The free and unprotected Topaze Reader allows files to be read, printed and exported without the requirement for an active license. A ‘slide presentation format’ has been added to use Topaze NL ‘live’ on a LCD projector or to copy/paste plots into PowerPoint™.