Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir

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Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir

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We have developed a comprehensive Petrophysical Characterization Workflow for a carbonate field, and to demonstrate it, we have created a Jupyter Notebook on GitHub. Our workflow comprises several steps, and we have used chatGPT3 to refine our python coding.

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# Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir
We have developed a comprehensive Petrophysical Characterization Workflow for a carbonate field, and to demonstrate it, we have created a Jupyter Notebook on GitHub. Our workflow comprises several steps, and we have used chatGPT3 to refine our python coding.

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/Costa_field_characterization3.gif)

---
>## Work repository is work in progress.
>
>There is a Geolog project that uses the same workflow and data that is also available at the following link:
>
>https://github.com/Philliec459/Characterization-of-a-New-Open-Source-Carbonate-Reservoir-Benchmarking-Case-Study-by-Costa
>
> 
> With this notebook we use our own normalized features (PHIT, RHOB and GR) and label (log10(Core_Perm)) vs. the 'black box' methods that are employed with some of the python packages. This way we can normalize and de-normalize as necessar knowing exactly how we performed the work.
> 
> We have added to our Characterization Notebook that uses Panel Widgets to select the well and well log analysis parameters:
> 
> 	CChartbook_Porosity_Optimized-Lithology_Perm_Thomeer_Saturations_Lasio_GPT_GitHub5.ipynb
> 	
> It is not totally straight forward, but please follow the directions in the Notebook:

> - Intitialize the entire Notebook in the beginning by running then entire Notebook first
> - Select the well and select your Neutron-Density crossplot porosity chart.
> - Use the interactive Lithology Optmimization and Pickett Plot to finalize on your petrophysical parameters. 
> - From that point on, run from the START POINT 2 as swhown in the Notebook
>
> For our characterization notebook we have added Andy McDonald's method to export las files for our results. The link to Andy's YouTube presentation is given in the notebook.
> **Watch Andy's YouTube presentation on this:**
>
> https://www.youtube.com/watch?v=GwAbfriuHr4
>
> 
> *Costa_Oil_Production.ipynb*
> 
>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/Costa_Production.gif)
>

---

# Introduction
**According to Costa(1):**
> *This work presents a new open-source carbonate reservoir case study, the COSTA model, that uniquely considers significant uncertainties inherent to carbonate reservoirs, providing a far more challenging and realistic benchmarking test for a range of geo-energy applications. The COSTA field is large, with many wells and large associated volumes. The dataset embeds many interacting geological and petrophysical uncertainties in an ensemble of model concepts with realistic geological and model complexity levels and varying production profiles. The resulting number of different models and long run times creates a more demanding computational challenge than current benchmarking models.*

> *The COSTA model takes inspiration from the shelf-to-basin geological setting of the Upper Kharaib Member (Early Cretaceous), one of the most prolific aggradational parasequence carbonate formations sets in the world. The dataset is based on 43 wells and the corresponding fully anonymized data from the north-eastern part of the Rub Al Khali basin, a sub-basin of the wider Arabian Basin. Our model encapsulates the large-scale geological setting and reservoir heterogeneities found across the shelf-to-basin profile, into one single model, for geological modelling and reservoir simulation studies.*

> *The result of this research is a semi-synthetic but geologically realistic suite of carbonate reservoir models that capture a wide range of geological, petrophysical, and geomodelling uncertainties and that can be history-matched against an undisclosed, synthetic 'truth case'. The models and dataset are made available as open-source to analyze several issues related to testing new numerical algorithms for geological modelling, uncertainty quantification, reservoir simulation, history matching, optimization and machine learning.*

In this GitHub repository we have used a new, comprehensive reservoir characterization database from Costa, Geiger and Arnold(1) We employed all the available well logs, Routine Core Analysis (RCA) and Special Core Analysis (SCAL and implemented our normal carbonate reservoir characterization workflow as discussed by Phillips (2). For this repository we did not use the 3D static or dynamic models, but we did use the time-series dynamic production and formation pressure data by well in Spotfire to better understand the dynamic aspects of the reservoir too. This is a rich dataset that needs to be explored further, more than what is presented in the scope of this project.

The RCA and SCAL core data as well as the 17 well logs provided as las files were used extensively in our Petrophysical evaluation. These data are all in a Geolog project that is included in this repository. The following layout depth plot display shows a typical well from the field and the analysis performed on each well.

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/Results.png)

The process used in this repository follows a tried and proven workflow as described by Phillips et al. (2) in the characterization of an Arab D carbonate reservoirs from Saudi Arabia. Core Porosity, Permeability, Petrophysical Rock Types (PRT), Capillary Pressure and capillary pressure-based saturations are all estimated or calculated within this workflow. Just as in previous studies, the core analysis database was used extensively as the foundation and calibration to these petrophysical interpretations.

Costa provided 110 High Pressure Mercury Injection (HPMI) core samples with RCA Porosity and Permeability. We performed Thomeer Parameter Analysis on each HPMI sample to establish our own, reservoir specific Thomeer Parameter Capillary Pressure core database used to mode saturations. In Geolog we fit the Thomeer hyperbola to all 110 HPMI samples and established the Thomeer parameters for each sample. We used python loglan code to load the High-Pressure Mercury Injection (HPMI) Core data directly from the Costa SCAL dataset into a Geolog Well and then modeled the HPMI data using the Thomeer parameters fitting the Thomeer hyperbola to each HPMI sample. This portion of the Geolog project serves an example as to how to build your own reservoir-specific core calibration database for their own Reservoir Characterization studies.

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/Thomeer_Parameter_fitting.gif)

### Suggested Carbonate Workflow:
The following workflow and processing are suggested to interrogate, process, interpret and model the petrophysical properties for this benchmark carbonate reservoir using Costa's RCA and High-Pressure Mercury Injection core database as calibration. The workflow consists of the following steps:

1) Interrogate the Well Log data and Costa calibration data using standard Geolog layouts, cross plots, and histograms; and then use a python loglan featuring Altair, which is interactive software driven from a Geolog Module Launcher.

##### Altair used to Interrogate the Costa Capillary Pressure curves and Petrophysical Rock Types (PRTs):

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/Costa_Pc2.gif)

2) Normally we would run MultiMin for a solid log analysis model using the typical minerals found in this reservoir; Limestone, Dolomite, and Illite. With MultiMin we always use environmentally corrected log data, calculating the uncertainties for each log curve employed in the analysis. However, to make this dataset more universal, we have employed python to perform our deterministic log analysis of the 17 HW wells. This code is provided in the Geolog project. We received these data as las files with a text file of log header data including X,Y locations, KB elevation and TD.  There were no directional survey data provided, so at this point we are assuming these wells to be vertical, and TVDss was calculated accordingly.

3) Use available core data from the representative reservoir/field to build a petrophysical model to estimate permeability for all wells in field using Geolog's Facimage. Our plan is to include a python loglan too using kNN with normalized input data that is weighted by Euclidean distances for each of the nearest neighbors to estimate permeability for each well.

4) Using the kNN estimated permeability and calculated Total Porosity (PHIT) from our log analysis, we queried Costa's core database to predict the following Petrophysical results:

- Thomeer Capillary Pressure parameters (Pdi, Gi and BVocci) for each pore system, i, over the entire reservoir interval for Capillary Pressure-based saturations
- Estimate the most dominant pore throat diameter at each level in the well calculated from the Thomeer parameters G and Pd. This exact mode of the pore throat distribution is calculated using the following equation:

*Mode of Pore Throat Distribution (microns) = exp(-1.15 * G1) * (214/Pd1)*

This exact Mode of the Pore Throat Distribution (PTD) is what Winland is trying to accomplish with r35 and Amaefule with FZI; however, they are not exact. The Mode of the PTD calculated from the Buiting equation is taken directly from the Capillary Pressure data and is the exact mode that correlates to other petrophysical parameters extremely well.

We used this mode to partition our data into Petrophysical Rock Types. If the Mode > 2 microns, then the PRT was a Macro porous rock. If the Mode > 0.1 micron and less that 2 microns, then this was Meso porous rock. If the Mode < 0.1 microns, then this rock was Micro porous rock.

5) Use the Thomeer Capillary Pressure parameters to model saturations based on the buoyancy due to fluid density differences at the height above the Free Water Level (FWL). In this instance we compare the Bulk Volume Oil (BVO) from our analysis vs. BVO from Thomeer-based capillary pressure saturations. We have used BVO since BVO is pore volume weighted, and Sw is not.

We did perform a Free Water Level (FWL) search for each well. We use the Thomeer parameters to model Capillary Pressure based saturations as shown below:

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/Thomeer_sats.png)

We vary the FWL from the highest potential FWL elevation down to the lowest potential FWL elevation for the reservoir and pick the FWL where the error between the BVO on logs vs. Capillary Pressure are at a minimum.

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/fwl_search.gif)

This is an example of the single well output from a typical FWL search. The FWL search was performed on all wells in the study.

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/FWLSearch.png)

Not all wells are useful in establishing the FWL. A few of the wells were too high where all we really were estimating was the Base of Reservoir (BOR) for those wells. There were also a few wells that were near 100% wet, and they were not used to establish the FWL surface. Eliminating these wells allowed us to establish the following FWL surface for this reservoir:

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/FWL_Surface.png)

Our estimated FWL surface is a plane but tilted with a high elevation of 8176 feet TVDss on the West, dipping to the East to a maximum FWL elevation of 8215 feet TVDss. Tilted FWL’s are quite prevalent in Saudi Arabia due to dynamic aquifer pressures, tilted structures and even subduction. We are not as familiar with the location of this field, but some of the conditions cound have been present in this field too. The FWL Surface was then used with the estimated Thomeer parameters on each well to calculate the final Capillary Pressure based saturations on each well in the field. The timing of drilling of each well is not understood, but HW-32 might be showing signs of water encroachment as seen in the figure below.

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/HW-32.png)

For the 3D static model, the Thomeer parameters on each well can be distributed thoughout the model or calculated from the Mode of the PTD that was calculated from a distributed Porosity and Permeability in the 3D static, fine-grid model. The points of intersection of the FWL surface at each well is then used to build the FWL plane. This FWL surface is then used with the modeled Thomeer parameters to estimate the original saturations for the field prior to production estimating OOIP from the FWL and above.

Finally, as with most of our studies we want to be able to integrate our Petrophysical findings with the dynamic production and pressure data to better understand the productive characteristics of this reservoir to be able to maximize recovery with sustained production over the life of this field.

>![Geolog_Image](https://raw.githubusercontent.com/Philliec459/Comprehensive-Petrophysical-Characterization-workflow-for-a-Carbonate-Reservoir/main/Costa_Spotfire.png)

---
### RESOURCES:
https://researchportal.hw.ac.uk/en/datasets/costa-model-hierarchical-carbonate-reservoir-benchmarking-case-st

https://github.com/Philliec459/Geolog-Used-to-Model-Thomeer-Parameters-from-High-Pressure-Mercury-Injection-Data

https://github.com/Philliec459/Geolog-Used-to-Automate-the-Characterization-Workflow-using-Clerkes-Rosetta-Stone-calibration-data

### REFERENCES:
1.  Costa Gomes J, Geiger S, Arnold D. The Design of an Open-Source Carbonate Reservoir Model. Petroleum Geoscience, 
    https://doi.org/10.1144/petgeo2021-067
2.  Phillips, E. C., Buiting, J. M., Clerke, E. A, “Full Pore System Petrophysical Characterization Technology for Complex Carbonate Reservoirs – Results from Saudi Arabia”, AAPG, 2009 Extended Abstract.
3.  Clerke, E. A., Mueller III, H. W., Phillips, E. C., Eyvazzadeh, R. Y., Jones, D. H., Ramamoorthy, R., Srivastava, A., (2008) “Application of Thomeer Hyperbolas to decode the pore systems, facies and reservoir properties of the Upper Jurassic Arab D Limestone, Ghawar field, Saudi Arabia: A Rosetta Stone approach”, GeoArabia, Vol. 13, No. 4, p. 113-160, October 2008.

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