Chert Content Determination via Quartz-Zircon Logging Ratios
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Solution Overview
Problem
Conventional logging tools cannot accurately distinguish chert from quartz in subterranean formations, leading to difficulties in drilling and completion operations due to chert's high rock strength and similar elemental composition.
Innovation Solution
Determining the amount of chert in a subterranean formation by calculating volumetric ratios of quartz to zircon using conventional logging data from both the selected formation and baseline formations, and applying a specific equation to derive the volumetric percentage of chert, which can then be used to adjust drilling or completion operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional logging tools are used to measure density, neutron, and resistivity, then the elemental composition can be identified, but chert cannot be distinguished from quartz due to their similar composition
Solution Approach 1:
The patent uses zircon as an intermediary indicator to indirectly determine chert content. Since zircon is specifically associated with chert nodules and has distinct logging tool responses, it serves as a mediator to identify chert that cannot be directly distinguished from quartz using conventional density, neutron, and resistivity measurements alone.
Solution Approach 2:
The patent changes the measurement parameters from direct elemental composition analysis to volumetric ratio analysis of quartz to zircon. By measuring the response of logging tools to these specific minerals and calculating their volumetric ratios, the system can indirectly determine chert content that would otherwise be indistinguishable from quartz.
2Measurement precision
If core samples are taken to accurately determine chert content, then identification accuracy improves, but cost and time increase
Solution Approach 1:
The patent replaces the mechanical system of core sampling, physical transport, and laboratory analysis with a logging tool-based measurement system. The logging tools measure density, neutron, and resistivity parameters in-situ, and computational algorithms process these measurements to determine chert content, eliminating the need for physical core samples and laboratory work.
Solution Approach 2:
The patent creates a virtual model of the formation composition by using logging tool responses to calculate volumetric ratios of minerals. This computational copy of the formation's mineralogy allows accurate chert identification without physical sampling, preserving time and resources while maintaining measurement precision.
3Productivity
If chert presence is not accurately identified, then drilling operations can proceed without adjustments, but drilling and completion operations face difficulties due to chert's high rock strength
Solution Approach 1:
The patent performs preliminary identification of chert zones using logging tools before drilling or completion operations begin. By determining the volumetric ratio of quartz to zircon and comparing it against baseline data from known hydrocarbon-bearing zones, the system提前 identifies areas with high chert content, allowing operators to plan appropriate drilling parameters and completion strategies in advance.
Solution Approach 2:
The patent establishes a feedback mechanism where logging data is continuously analyzed to determine chert content, which then feeds back into drilling and completion operation planning. The calculated volumetric ratios and chert identification results provide real-time feedback that allows operators to adjust their operations to account for high rock strength zones, improving both productivity and operational reliability.
Data Source
AI summary
Techniques for determining an amount of chert in a rock formation include identifying first logging data for a selected zone of a first subterranean formation that includes chert, quartz, and zircon; identifying second logging data for a second subterranean formation that is different than the first subterranean formation, the second subterranean formation including chert, quartz, and zircon; determining a first volumetric ratio of quartz to zircon in the selected zone based on the first logging data; determining a second volumetric ratio of quartz to zircon based on the second logging data; determining a maximum value of the second volumetric ratio; and calculating, based on the first and second volumetric ratios and the maximum value of the second volumetric ratio, a volumetric percentage of chert in the selected zone.