Automated Geosteering via Gamma Log Correlation
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Solution Overview
Problem
Current geosteering methods for directionally drilled wells rely heavily on manual correlation of gamma log data, leading to inconsistent results and subjective bias, as they require geosteerers to visually match gamma traces between wells, which is time-consuming and prone to errors.
Innovation Solution
A system and method that automatically determine the path of a directionally drilled well by solving a minimum travel distance problem using gamma log readings from the target well compared to an offset well, represented as a two-dimensional matrix of nodes, where the distance between nodes is calculated based on gamma reading differences, and a numerical algorithm is used to find the optimal stratigraphic blocks that define the well's path within the target formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual correlation of gamma log data is used, then geosteerers can visually match gamma traces between wells, but the process is time-consuming and prone to errors
Solution Approach 1:
The patent replaces the manual mechanical process of visually matching gamma traces with an automated computer-based system. The system automatically correlates gamma log data from the target well with the typelog by processing digital data through algorithms, eliminating the need for manual visual comparison while improving both speed and consistency of the correlation process.
Solution Approach 2:
The system creates a digital copy of the gamma log data from both wells and processes these copies through computational algorithms. By working with digital replicas rather than physical or manual data, the system enables rapid, repeatable correlation analysis without the time constraints and human errors associated with manual methods.
2Measurement precision
If manual manipulation of strat block lengths and angles is performed, then geosteerers can try to get a fit between well logs, but the results are subjective and inconsistent
Solution Approach 1:
The patent replaces subjective manual manipulation of stratigraphic blocks with an objective computational algorithm. The system automatically adjusts and optimizes block lengths and angles based on mathematical criteria that minimize the difference between well logs, eliminating the subjectivity and inconsistency inherent in manual geosteerer judgments.
Solution Approach 2:
The system incorporates feedback mechanisms where the correlation quality is continuously evaluated and the stratigraphic block parameters are iteratively adjusted based on the degree of match between the target well log and typelog. This feedback loop ensures consistent, objective optimization of the correlation rather than relying on geosteerer intuition.
3Productivity
If automated numerical algorithms are used to solve minimum travel distance problem, then objectivity and efficiency are improved, but the system complexity increases
Solution Approach 1:
The patent segments the complex well path determination problem into smaller manageable components: discrete stratigraphic blocks with defined parameters, nodes representing specific locations, and edges representing possible paths. This segmentation allows the complex minimum travel distance problem to be solved through systematic algorithmic processing of simplified elements rather than handling the entire complex problem at once.
Solution Approach 2:
The system transforms the three-dimensional well path problem into a two-dimensional matrix representation with nodes and edges. By projecting the complex 3D spatial and stratigraphic problem onto a 2D computational grid, the system simplifies the algorithmic processing while preserving the essential relationships needed for accurate path determination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides an objective and efficient method for determining the well's path, reducing human error and subjectivity, and enabling precise geosteering to maintain the wellbore within the target formation, thereby enhancing hydrocarbon production and minimizing gas or water breakthrough.
Implementation Method 1
a gamma log, or 'gamma ray log' is obtained using a downhole tool that measures naturally occurring gamma radiation emitted from the rock units. It is well known that different rock types emit different amounts of radiation which provides a means for identifying lithologic units in the subsurface
Data Source
AI summary
There is provided herein a system and method for automatically determining a path within a target rock unit of a directionally drilled well (a target well) using log readings, e.g., gamma log readings, taken in the target well as compared with log readings (a typelog) taken in a well that penetrates the target rock unit (an offset well). Most specifically, in some embodiments the path of the target well within the target rock unit will be obtained by solving a minimum travel distance problem which uses distances that are based on differences between well log readings in the target and offset wells. Solution of this problem will yield a collection of stratigraphic blocks lengths and dips that define a path of a well in a subsurface through the target formation or rock unit.