General Data

Open hole logs are loaded for depth matching purposes and to complement the cased hole log (CHL) interpretation. Also, a deviation survey is used quantitatively in PL interpretation and brings important qualitative information for the interpretation of other logs.

In addition to traditional Open hole (OH) logs, borehole images, Cement logs including CBL, VDL and Impedance maps and any other array data type, typically DLIS files, can be loaded to supplement the CHL analysis.

If saturation and porosity logs are also loaded, Emeraude will automatically create a track displaying the formation fluid volumes.

Completion Details

Here, the internal diameter (ID), perforation depth and reservoir zones, markers, pipe roughness and deviation are loaded.

These inputs are used for Zone rate calculations of the PL interpretation and qualitatively for the other logs.

Well Sketch

It is possible to create a completion diagram of the well, by selecting completion items (casing, tubing, cement, etc.) from a list.

This is for illustrative purposes only, the diameter and length of the components are not used as an input for the calculation process. The well schematic can be shared with other K-W modules.

Load CHL Data

Passes and stationary data are loaded from LIS, DLIS, LAS and ASCII files.

Automatic tracks are built to give an instant view of the log data, whilst customized views can be created through the use of snapshots and templates, permitting fast navigation through the data.

Array data type can be loaded directly (DLIS files) or created at the loading stage from individual/multiple LAS or .csv files. This is the default data format for DTS, MFC and Noise data.

Editing Data

The raw CHL data normally requires editing before an interpretation can be performed.

Emeraude contains a broad range of editing options: lateral average, depth stretch, shift, delete data and fill, hide data, merging, splicing, derivative, sampling, user formula module, etc...

Cross-plots and Histograms

Petrophysical workflows typically include cross-plotting measurements in order to establish trends, patterns and zones with different properties. Emeraude offers 4D crossplots (X, Y, colour, size).

Similarly, histogram plots are crucial to understand the distribution of the measurements over the interval of interest and quickly spot outliers.

Define Reference Channels

The reference channels will be used to compute the PVT properties and also in the regression during zone rates calculation.

In Emeraude, pressure temperature and any relevant hold-up or density channel need to be defined. If more than one pass is selected, a lateral average will be applied.

PL Tool Configuration

Density tool type needs to be defined to allow the relevant corrections are applied in the calculation scheme. The spinner blade diameter must be entered to compute the velocity profile correction factor. A built-in list of capacitance tools is included for the different vendors, with their respective calibration charts.

Spinner Calibration and Velocity Generation

The spinner measures revolutions per second (RPS), but the interpreter needs fluid velocity and rates. To transform spinner RPS and cable speed to fluid velocity, the spinner calibration parameters need to be known. When sufficient passes are available, an in-situ spinner calibration can be performed.

Different calibration modes and editing tools are available on user defined spinner calibration zones. The interpolation between calibration zones may be modified, depending on the fluid distribution in the pipe.

Once the spinner calibration parameters are known, the apparent velocity is calculated for each pass and each spinner, where applicable.

For MPT spinners, a Hold-up weighted spinner calibration option is offered to handle toolstring rotation in stratified flow conditions.

PVT

PL phase calculation is highly sensitive to the PVT. Consequently, when calculating the rates at downhole conditions, a number of PVT properties are required. Also, to convert the downhole rates to surface conditions, the volume factors need to be known.

Black-oil PVT offers a wide choice of correlations, which can be viewed and matched to user-defined measurements. PVT tables may also be loaded. If the PVT is zoned, properties are redefined for each inflow zone. A steam-water model is available to analyse steam injection wells.

MPT Processing

In the presence of MPT sensors, an average value of holdup and rates is computed at every depth, from the discrete measurements.

At every depth, an average value of holdup and rates, from the distributed measurements, is computed.

The MPT processing first maps the measurements using 2D models and then integrates holdups and velocities to compute the rates. The mapping can be constrained by the user, by, for example, forcing stratification and accounting for conventional measurements.

N number of passes can be stacked (or combined) into a single equivalent ‘virtual’ pass, which contains N times the number of probes, compared to the original tool.

Rate Calculation

The rates are calculated in selected intervals of the log, and a continuous profile can be created.

Rate calculation is treated as an optimization problem using nonlinear regression, with full flexibility in the type and number of input measurements. Calculations may be zoned or continuous. The zoned calculation focuses on user defined stable flow intervals. The continuous method seeks agreement everywhere on the logs and the holdups are treated as variables, allowing a possible deviation from the slip models. The zoned method works well most of the time and it is very fast. The continuous method may provide a better answer in complex cases and when attempting to match temperature. The user has the choice.

Global Regression

The global regression solves for the contribution of the inflow intervals instead of the selected calculation zones only. Such regression solves for the entire well at once, allowing the user to impose constraints such as the contribution sense, surface rates, etc. It is also possible to fix any particular contribution to a fixed or null value.

Log and Results

The interpretation’s result is presented in the form of a cumulative and contribution profiles with phase rates. This can be at downhole or standard conditions.

Numerical outputs can be obtained from the summary table, which shows the cumulative and contribution rates, and velocities of each phase, with the PVT properties at the level of each inflow zone

Thermal/DTS

Increasingly, wells are completed with fibre optic distributed temperature sensors (DTS). Even in a conventional PL job, the spinner may fail or give an erroneous response under certain circumstances such as counter current or high viscosities. If the thermal properties of the fluids, completion and formation are known it is possible to perform quantitative production or injection profiling.

Coupling energy and mass balance equations, Emeraude offers methods for production and injection profiling and annular leak detection. Also, Emeraude incorporates specific formulations for Water Injection Fall-off (warmback) and steam injection.

Due to the broad application and various types of models used in thermal/DTS data, a specific workflow was developed. Visit the Thermal page to learn more about thermal solutions in Emeraude and Rubis.

DAS

Distributed Acoustic Sensing (DAS) data can be loaded from .h5 files, following the PRODML DAS standard. DAS raw, spectra, and frequency band extracted (FBE) are automatically displayed versus depth or time as array images. It is possible to edit the data, extract particular frequencies, and display the array in 3D.

Completion Description

Multi-Finger Caliper (MFC) statistics including penetration and reduction are based on the nominal pipe diameters (ID, OD). The user needs to enter the details for all logged pipe.

Centralization

Due to toolstring weight, the MFC tool is not always concentric with the pipe. The different arms reflect this eccentricity by displaying a large variation of radius measurements, typically with a sinusoidal distribution.

The centralization algorithm fits, at every depth, an ellipse or circle, from where the pipe centre can be extracted and the arm radii recomputed. The algorithm removes a number of measurements to avoid including holes or deposition in the regression.

Bad Fingers and Filtering

When one or more arms show invalid data (ie clogged, dead or with electronic problems), it is possible to replace its value by an average of the adjacent arms, or using the median or mean at that depth.

It may also be necessary to filter the data to remove telemetry spikes.

Recalibration

The MFC outputs a number of radius values (one for each finger), which are based on surface calibration that relate the transducer electric output (voltage) to the actual radius value. This calibration may not be valid due to finger wear or temperature. The arm values can be recomputed in Emeraude based on statistics (mean, median) or known ID.

Joints Identification

Even though Emeraude calculates statistics at every depth, the analyst is typically interested in the main pipe bodies and not in the connections. Joints are automatically identified based on threshold values of penetration, CCL and metal loss. The user can constrain the minimum pipe length and add offsets between the connection and the beginning of the joint definition.

Joints table

The final product is a Joint table, where the main statistics for each joint are displayed. From here, the analyst can quickly spot the joints that are more affected, and navigate to them to take snapshots or cross-sections of the different features.

MFC Display

MFC data can be displayed as 2D maps, with the colour representing the finger radius, cross sections and 3D images. All plots are automatically refreshed after applying any editing or processing step.

Data Loading

Noise data is typically acquired at stations to reduce the noise induced by cable movement, not representative of the fluid. These stations may be very finely spaced and hundreds recorded.

Emeraude can load time-driven .csv or las files with changing depth. Stationary data is automatically identified from the cable speed or depth variation. For memory jobs, it is possible to load noise and depth data from different files and synchronize these by applying time shifts.

Vs. Depth Spectrogram

For each station, a representative noise spectrum is extracted based on statistical or instantaneous values. Combining all stations, the final versus depth spectrogram is obtained, together with the noise normalized energy and spectrum centroid. Spectrogram may be displayed interpolated or at depth of the station.

It is possible to select individual frequency bins and apply further calculations using the Mathpack or external DLLs.

Sigma Definition

The logged sigma represents a volume-weighted response of the different formation components (fluids, matrix, shale). The user enters the sigma values for all the components of the system.

Cross-plots

The previous definition of the sigma components can be refined through the use of specific cross-plots. Different variables are plotted depending on the available data, which will lead to the sigma values for the matrix, water and hydrocarbon.

The cross-plots and sigma definition may be zonal in case of variable lithology, hydrocarbon properties or water salinity.

Water Saturation

Once the definition of the sigma components and effective porosity is complete, the water saturation is computed.

Time-lapse

Saturation logs recorded at different times, and possibly through different techniques, can be plotted together in a ‘Pore volume analysis’ track, in order to understand the evolution of the water saturation front.

Data Loading

Cement logs from sonic or ultrasonic tools can be loaded in Emeraude in LAS and DLIS format. Emeraude automatically identifies the relevant mnemonics of the main Cement evaluation tools in the industry.

Cement Data Display

Cement logs display is facilitated by using predefined templates, arranging the available data in a specific layout. Most cement maps have a built-in associated colour scale. Impedance and sectors amplitude maps can be displayed in 3D. Waveforms from the VDL can be extracted at any depth.

Cement Evaluation

Bond index and attenuation can be calculated from CBL data. An isolation analysis workflow is offered, consisting in the evaluation of the casing-cement bond, cement-formation bond, and channelling. Casing connections can be identified and removed from the analysis.

Evaluation Results

The potential for hydraulic isolation is presented in a dedicated track as a traffic light system. The results are also available as tables, presenting the main parameters for each interval with different properties, and per joint.

Data Loading

Thickness data from Ultrasonic or electromagnetic remote-field eddy currents (single barrier) tools can be in LAS and DLIS format. The pipe nominal parameters and required to extract pipe statistics.

Thickness Computation

Emeraude allows computing the thickness from electromagnetic tools. Calibration passes at various frequencies are used to obtain the pipe properties. Thickness is computed from phase values from the various receptors.

Results

Joints identification is available for thickness data, to remove the effect of the connections.

Thickness statistics are presented as logs and as results tables. Processed data can be displayed in 3D or as cross-sections.

Selective Inflow Performance (SIP)

In a multirate PLT, the well is logged at different surface rates. For each choke setting, the contribution of the zones and corresponding bottom hole pressures will change. Plotting the bottom hole flowing pressure versus the contributions for each zone, it is possible to obtain an IPR curve for each producing layer, and therefore quantify important reservoir parameters, such as reservoir pressure, productivity index and absolute open flow.

In Emeraude, an SIP analysis can be made with a few clicks. Pseudopressures can be used for gas. An unlimited number of SIP’s can be created and compared. Each zone can be assigned a different model: straight line, C&n or L.I.T. The SIP can use the total, phase or total liquid rate. Data may be downhole or from surface. Pressure datum correction and composite IPR’s are available.

Apparent Permeability (APERM)

Estimation of effective permeability at reservoir scale is fundamental for an accurate reservoir model. In carbonates, the permeability in vuggy or fractured intervals can be dramatically different from the matrix permeability measured in core plugs. The apparent permeability based on PLT data may be the solution for a field-scale characterization.

This method corrects, with the PL interpretation, the open-hole effective permeability. It uses an IPR relationship where the relevant reservoir or perforation parameters are defined zone by zone. The method is implemented for single-phase liquid, liquid mixture, or for gas using pseudopressures.

Multilayer Transient Analysis

In PTA it is possible to define a multilayer model with different petrophysical properties, unequal reservoir pressures and varying skin. The layer contribution will be simulated, and these can be used to adjust the layer parameters.

From Emeraude, it is possible to transfer the production profile to Saphir for multilayer transient analysis. Also, the initial layer pressures can be based on SIP analysis.