3D & 4D Closed-loop™

Identification of by-passed oil is the key to unlock the remaining potential of mature fields. Building a reliable reservoir model through consistent integration of static and dynamic reservoir data is the key to successful Locate-the-Remaining-Oil (LTRO) activities.

Challenges

A large number of reservoir geomodeling projects do not meet the project objectives. It is not uncommon that resulting models exhibit extreme differences between prediction and observed facts. In traditional approaches, reservoir engineers only use production data or other types of well data to screen and refine the models. Due to the lack of efficient tools and workflow, it is still uncommon to perform history matching of seismic data. As a result, the production-data-matched models are usually not geologically-consistent. Although they may be used for production forecasting, reserve estimation and uncertain analysis. It is not unexpected that their predictive capability of the location of remaining oil is questioned. 

Benefits

  • Independent check of the petrophysical
    evaluation of porosity, Vshale (net-to-gross), and saturation
  • Improved reservoir understanding without acquiring new data, thus no further addition of CAPEX
  • Unrivalled accuracy in the delineation of remaining oil enables cost-effective in-fill drilling and reservoir management in a mature field
  • Reduce cost and turnaround time of traditional history matching project, eliminating the cost of deferred decisions.
  • Handle data redundancy and inconsistency in a systematic, probabilistic manner

Approach

Promoters of sophisticated (and expensive) history matching software packages often assert that the sensitivity analysis, screening, and model refinement steps can all be done in one single black-box approach.  However, the truth is that no single approach is appropriate for all circumstances. 

Regardless of the history matching workflow, the reservoir engineer and geomodeling team have several important tasks that no assisted history matching method should do automatically:

  • the interpretation of reservoir data,
  • the parameterization of the reservoir model(s), and
  • the decision about the uncertainty of the input parameters and reservoir data.

For closing the loop between the reservoir model and seismic data, 

  • Quantification of noise 
  • Need for understanding the mismatch between synthetic and observed seismic data (e.g. errors in rock physics model, noise, incorrect reservoir properties, etc.)
  • Interpretation unambiguity due to competing production effects and their combined nonunique 4D signatures
  • Need for the addition of flow barriers 
  • Balance the influence of 4D seismic and production data

 

These tasks are necessarily subjective decisions and have extreme importance on the quality of the model (and hence the history match).  Clearly, the interpretations, assumptions, and decisions of the geomodeling team which ultimately lead to a numerical model of the reservoir should be challenged and questions during the modelling process. The sequential approach with the combined use of computer-assisted approach and manual editing is most widely used with the focus given to updating different parameters in different steps. 

Parameters to be updated in 3D & 4D Closed-loop™

Approach

Promoters of sophisticated (and expensive) history matching software packages often assert that the sensitivity analysis, screening, and model refinement steps can all be done in one single black-box approach.  However, the truth is that no single approach is appropriate for all circumstances. 

Regardless of the history matching workflow, the reservoir engineer and geomodeling team have several important tasks that no assisted history matching method should do automatically:

  • the interpretation of reservoir data,
  • the parameterization of the reservoir model(s), and
  • the decision about the uncertainty of the input parameters and reservoir data.

For closing the loop between the reservoir model and seismic data, 

  • Selection of seismic data due to the spatially varying noise level
  • Need for understanding the mismatch between synthetic and observed seismic data (e.g. errors in rock physics model, noise, incorrect reservoir properties, etc.)
  • Interpretation unambiguity due to competing production effects and their combined nonunique 4D signatures
  • Need for the addition of flow barriers 
  • Balance the influence of 4D seismic and production data

 

These tasks are necessarily subjective decisions and have extreme importance on the quality of the model (and hence the history match).  Clearly, the interpretations, assumptions, and decisions of the geomodeling team which ultimately lead to a numerical model of the reservoir should be challenged and questions during the modelling process. The sequential approach with the combined use of computer-assisted approach and manual editing is most widely used with the focus given to updating different parameters in different steps. 

Parameters to be updated in 3D & 4D Closed-loop™

Solution

PEM calibration on multiple cross-plot template simultanously 

PEM-model creation and calibration

Along with applicability to the specific reservoir scenario, calibratebility is an indispensable criterion for selection of the optimum rock-physics model. This is not a trivial task and the challenges are often not properly dealt with by the G&G team. 3D & 4D Closed-loop™ contains a complete set of widely-used PEMs chosen based on our 20 years experience in the North Sea. It also allows the users to easily create and calibrate a custom PEM with powerful sensitivity and calibration functionalities. 

PEM-model creation and calibration

Along with applicability to the specific reservoir scenario, calibratebility is an indispensable criterion for selection of the optimum rock-physics model. This is not a trivial task and the challenges are often not properly dealt with by the G&G team. 3D & 4D Closed-loop™ contains a complete set of widely-used PEMs chosen based on our 20 years experience in the North Sea. It also allows the users to easily create and calibrate a custom PEM with powerful sensitivity and calibration functionalities. 

PEM calibration on multiple cross-plot template simultanously 

Seismic model validation

Simulation to Seismic (Sim2Seis) is a forward modelling technique used to predict/generate the synthetic seismic response from a static or dynamic reservoir model. There are two key components of a Sim2Seis workflow: reservoir model (geological and/or simulation model) and petro-elastic models (PEMs). PEMs are rock physics functions which relate reservoir properties such as rock types, porosity and fluid saturation to the elastic properties such as compressional and shear velocities, and density. Predicted elastic properties are used to compute reflection coefficients when convolved with a wavelet generate a synthetic seismic volume (1D or 3D).

 

 

Seismic model validation

Simulation to Seismic (Sim2Seis) is a forward modelling technique used to predict/generate the synthetic seismic response from a static or dynamic reservoir model. There are two key components of a Sim2Seis workflow: reservoir model (geological and/or simulation model) and petro-elastic models (PEMs). PEMs are rock physics functions which relate reservoir properties such as rock types, porosity and fluid saturation to the elastic properties such as compressional and shear velocities, and density. Predicted elastic properties are used to compute reflection coefficients when convolved with a wavelet generate a synthetic seismic volume (1D or 3D).

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A variety of grid properties editing tools are available allowing users to interactively test a specific scenario

Interactive editing of grid properties

After the difference between observed and synthetic seismic is analyzed, and the reasons that cause such discrepancies full understood, editing the grid properties cannot be easier in 3D & 4D Closed-loop™. The software offers a full spectrum of editing options to suit different circumstances.

Interactive editing of grid properties

After the difference between observed and synthetic seismic is analyzed, and the reasons that cause such discrepancies full understood, editing the grid properties cannot be easier in 3D & 4D Closed-loop™. The software offers a full spectrum of editing options to suit different circumstances.

A variety of grid properties editing tools are available allowing users to interactively test a specific scenario