In-Situ Stress Estimation by Back Analysis Based on Wellbore Deformation with Consideration of Pore Pressure
Bibliographic record
Abstract
In oil and gas industry, wellbore stability control is paramount in an operation. It is essential to have information of the in situ stresses in well planning and prevention of wellbore failure. However, the current available measurement methods for in situ stresses in petroleum engineering are costly and often give scattering results. In this paper, a more practical displacement-based back analysis technique is proposed to determine the magnitude and orientation of the in situ stresses. The purpose is to provide an alternative tool for small operators in petroleum industry. An analytical solution is derived from displacement-stress relationship around a well in an isotropic rock with consideration of pore pressure. This method can be applied to calculate the displacement at any point around the well induced by drilling. In a reversed order, it can be used to calculate the in situ stresses from measured displacements at a number of locations on the borehole wall. For practical purpose, drained and undrained constitutive 2D models using measured diametrical deformation at different locations around a borehole wall as the input data have been developed to estimate the in situ stresses. Program codes in Matlab were written to facilitate the analysis under different conditions. An example is introduced to test the model and the program. The results validated this back-analysis approach and made a reliable estimation of the in situ stresses. The effects of pore pressure are also evaluated and are found to have significant impact on the shape of wellbore deformation. This impact differs for the drained and undrained conditions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".