Petrophysics With Python

Dilshad Raza
Institute of Geology,
University of the Punjab, Lahore 54590, Pakistan.

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Repo:

This Repo Contains Notebooks in which I have explored and analyzed different aspects of Petrophysics with Python.

Introduction:

The term "petrophysics" was coined by G.E. Archie and J.H.M.A. Thomeer in a quiet bistro in The Hague. By their definition, petrophysics is the study of the physical and chemical properties of rocks and their contained fluids.The Society of Petrophysicists and Well Log Analysts (SPWLA) mission is to increase the awareness of petrophysics, formation evaluation and well logging best practices in the oil and gas industry.

Python

Python is a popular programming language. It was created by Guido van Rossum, and released in 1991. Python is a high-level, interpreted, general-purpose programming language. Its design philosophy emphasizes code readability with the use of significant indentation. Python is dynamically-typed and garbage-collected.

Python and Petrophysics

Use of python to explore and visualise the well log data, doing machine learning and applying AI methods is increasing rapidly because of easy to understand syntax of the programming language and the ability to use different modules that can be used to work on Geosciences data inluding Well log data, Seismic Sections data, Data with Geospatial References.

Role of petrophysicist

Petrophysics emphasizes those properties relating to the pore system and its fluid distribution and flow characteristics. These properties and their relationships are used to identify and evaluate:

• Hydrocarbon reservoirs
• Hydrocarbon sources
• Seals
• Aquifers

The petrophysicist or petrophysical engineer practices the science of petrophysics as a member of the reservoir management team. The petrophysicist provides answers on products needed and used by team members, as well as physical and chemical insights needed by other teammates.

The reservoir and fluid characteristics to be determined are:

• Thickness (bed boundaries)
• Lithology (rock type)
• Porosity
• Fluid saturations and pressures
• Fluid identification and characterization
• Permeability (absolute)
• Fractional flow (oil, gas, water)

It is easy to define these characteristics and to appreciate their part in the assessment of reserves. The difficult part comes in determining their actual value at a level of certainty needed to make economic decisions leading to development and production. The seven characteristics listed are interdependent (i.e., to properly determine porosity from a wireline log, one must know the lithology, fluid saturations, and fluid types). The science of petrophysics is then used to unscramble the hidden world of rock and fluid properties in reservoirs from just below the Earth’s surface to ones more than four miles deep. The petrophysicist then takes on many characteristics of the fictional sleuth Sherlock Holmes to extrapolate, from the most meager of clues, the true picture of the subsurface reservoir using dogged determination to wrest all possible information from the available data, all the while enjoying the thrill of the hunt.

How does the petrophysicist solve this difficult problem? Archie’s general method is to subdivide the problem into smaller segments and iterate using all data until all data agree. One starting point is to determine rock types (petrofacies) wherein we identify:

• Pore type
• Pore size distribution
• Pore throat type
• Pore throat distribution

When coupled with fluid type, one can establish a capillary - pressure model that will lead to understanding in-situ fluid saturations and fluid flow. However, the tools available to the petrophysicist are:

• Mud logging (solids, liquids, gasses, volumes, rates, concentrations, and temperature)
• Measurement while drilling (MWD) and Logging while drilling (LWD)
• Wireline logging (open- and cased-hole)
• Core sampling [(wireline (percussion and drilled) and whole] and core analysis
• Fluid sampling (wireline and/or drillstem tests)

Tools for Petrophysics

Here is the table of Tools that are appropriate for studying different petrophysical properties.

Petrophysical property determination

Petrophysical analysis can be used for the following:

• Lithology determination
• Net-pay (or pay/nonpay) determination
• Porosity determination
• Fluid-contacts identification
• Water-saturation determination
• Permeability determination

References

• Crain, E.R. 1986. Log Analysis Handbook. Tulsa, Oklahoma: PennWell.
• Dewan, J.T. 1983. Essentials of Modern Openhole Log Interpretation. Tulsa, Oklahoma: PennWell.
• Log Interpretation Principles/Applications. 1989. Houston, Texas: Schlumberger.
• Introduction to Wireline Log Analysis. 2002. Houston, Texas: Baker Hughes Inc.
• Fundamentals of Rock Properties. 2002. Aberdeen: Core Laboratories UK Ltd.