Core Sample Selection via Rock Quality Classification

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Solution Overview

Problem

The high cost and time-consuming nature of special core analysis (SCAL) for core samples in petroleum exploration make it economically infeasible for all samples, often leading to undersampling or oversampling, resulting in inaccurate representations of formations and increased costs.

Innovation Solution

A method for selecting representative core samples through a preliminary analysis that determines rock quality values, static rock types, and sampling subspaces, allowing for a more intensive SCAL on a reduced number of samples, optimizing hydrocarbon production while minimizing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If special core analysis (SCAL) is conducted on all core samples, then comprehensive formation property information is obtained, but time and cost increase significantly

Engineering Contradiction:

Improveformation property informationVSAvoidcore sample assessment time

Core Design Contradiction:

Loss of informationVSLoss of time

Solution Approach 1:

The patent segments the core sample population into different groups based on rock quality classification (RQC) and formation zone characteristics. By dividing samples into high-quality, medium-quality, and low-quality groups, the system applies SCAL selectively to representative samples from each segment rather than all samples, thus maintaining information completeness while reducing overall assessment time and cost.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary rock quality classification and formation zone identification on all core samples before conducting SCAL. This preliminary sorting action identifies which samples are most representative of different formation characteristics, allowing SCAL to be focused on a reduced set of priority samples that will provide the most valuable formation property information.

Inventive Principle:

Principle #10Preliminary action

2Loss of information

If SCAL is conducted on all core samples, then accurate formation representation is achieved, but costs become prohibitive

Engineering Contradiction:

Improveformation representation accuracyVSAvoidcore sample assessment cost

Core Design Contradiction:

Loss of informationVSLoss of energy

Solution Approach 1:

The patent applies different levels of analysis quality to different core sample groups based on their rock quality classification. High-quality samples receive full SCAL treatment, medium-quality samples receive targeted analysis, and low-quality samples receive minimal or no SCAL. This local quality differentiation ensures accurate formation representation from the most representative samples while significantly reducing overall assessment costs.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of analysis intensity based on rock quality classification parameters. By using RQC scores and formation zone characteristics as selection criteria, the system dynamically adjusts which samples undergo full SCAL versus reduced analysis, optimizing the balance between formation representation accuracy and assessment cost.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If a limited number of core samples are selected for SCAL, then costs and time are reduced, but risk of undersampling and inaccurate formation representation increases

Engineering Contradiction:

Improvecore sample assessment costVSAvoidformation representation accuracy

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent incorporates feedback mechanisms where preliminary core analysis results (rock quality classification, formation zone identification) feed into the SCAL sample selection process. This feedback loop ensures that samples selected for SCAL are those most likely to provide accurate formation representation, reducing the risk of undersampling while maintaining cost efficiency.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces manual, subjective sample selection with an automated computational system that uses rock quality classification algorithms and formation zone identification. This substitution of mechanical/subjective selection with automated objective criteria ensures consistent, reliable sample selection that minimizes undersampling risk while reducing costs associated with manual evaluation of all samples.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10969323B2Systems and methods for special core analysis sample selection and assessment

Publication Date: 2021.04.06 SAUDI ARABIAN OIL CO

AI summary

Provided are embodiments of conducting a special core analysis (SCAL) of an identified subset of core samples. Embodiments include determining rock quality values for core samples extracted from a subsurface hydrocarbon formation, and determining static rock types corresponding to the core samples based on the rock quality values. For each of the static rock types identified, scaling the corresponding rock quality values to generate scaled rock quality values, and determining a number of subspaces (ns) for the static rock type based on the scaled rock quality values. For each subspace of the static rock type: identifying a number (k) of most similar rock quality values in the subspace; identifying a subset of the core samples corresponding to the most similar rock quality values identified for the subspace of the static rock type; and conducting a SCAL of the core samples of the subset of the core samples.