Geosteering Inverse Problem Extrapolation Thin Formations
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Solution Overview
Problem
Existing geosteering methods face challenges in accurately determining the boundaries between thin oil and gas bearing formations during horizontal well drilling, leading to difficulties in maintaining the borehole within the target formation due to inadequate resolution of gamma ray logging data.
Innovation Solution
The method involves processing natural gamma ray data to solve the inverse problem for borehole positions, extrapolating formation boundaries ahead of the drill bit, and adjusting the borehole trajectory to reach the target layer by utilizing the sphere of influence of gamma radiation, allowing for precise guidance within the target formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional gamma ray logging data is used for geosteering, then the drilling process can proceed, but the resolution is insufficient to accurately determine boundaries in thin formations
Solution Approach 1:
The method performs preliminary actions by solving the inverse problem and extrapolating formation boundaries ahead of the drill bit before actually reaching those boundaries. This allows the drilling team to anticipate boundary locations and adjust the borehole trajectory proactively, improving boundary determination accuracy before the limitation of current gamma ray data resolution becomes critical.
Solution Approach 2:
The invention introduces an intermediary computational process (solving the inverse problem and extrapolating boundaries) that mediates between the limited gamma ray logging data and the need for accurate boundary determination. This intermediary process enhances the information content of the raw gamma ray data, enabling accurate boundary identification in thin formations despite the inherent resolution limitations of the logging tool.
2Manufacturing precision
If the borehole trajectory is adjusted frequently to maintain position in thin formations, then the drill bit can stay within the target layer, but the complexity of real-time decision making increases
Solution Approach 1:
By solving the inverse problem and extrapolating boundaries ahead of the drill bit, the system performs preliminary trajectory planning before the drill bit reaches critical boundary zones. This reduces the need for frequent reactive adjustments and simplifies real-time decision-making while maintaining high borehole position accuracy in thin formations.
Solution Approach 2:
The method implements a feedback mechanism where gamma ray measurements are continuously processed through the inverse problem solution, and the extrapolated boundary information feeds back into trajectory adjustment decisions. This closed-loop feedback system maintains borehole position accuracy while systematic processing reduces the perceived complexity of real-time operations.
3Loss of information
If gamma ray data is collected at multiple borehole positions, then better boundary information can be obtained, but the time required for data collection and processing increases
Solution Approach 1:
The inverse problem solution and boundary extrapolation are performed preliminarily at each measured position before moving to the next position. This allows the system to accumulate boundary information efficiently from multiple positions while minimizing idle time, as the computational processing occurs in parallel with or immediately following data acquisition at each location.
Solution Approach 2:
The method maintains continuous useful action by processing gamma ray data through the inverse problem solution continuously as the drill bit progresses through the formation. This continuous processing approach ensures complete boundary information is obtained from multiple positions without interrupting the drilling operation, thereby minimizing time loss while maximizing information completeness.
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 enables accurate determination of formation boundaries and adjustment of the borehole trajectory, ensuring the drill bit remains within the target layer, even when the formation is thin, thereby optimizing the drilling process and maximizing recovery from oil and gas reservoirs.
Implementation Method 1
natural gamma ray data is obtained for a plurality of borehole positions along a proposed borehole trajectory through a formation having formation layers of different lithologies
Data Source
AI summary
In a method for drilling a borehole real time geosteering data, including natural gamma ray data is obtained for a plurality of borehole positions for drilling a borehole along a projected trajectory. A formation layer having a thickness equal to or greater than the natural gamma ray sphere of influence and having a first lithology is identified. Data is processed for subsequent borehole positions. Upon location of the boundary of a formation layer of different lithology within the natural gamma ray sphere of influence, at least two points of the different formation layer boundary are determined by using the inverse problem methods, and an extrapolation ahead of the drill bit of at least two points is made utilizing the boundary to determine whether to change the borehole trajectory.