| Autor: |
Prahlad Yadav, Saad Imtiaz, Satya Perumalla, Hemant Singh |
| Rok vydání: |
2017 |
| Předmět: |
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| Zdroj: |
Day 3 Wed, November 15, 2017. |
| Popis: |
In the Middle East, a significant amount of Non-Productive Time (NPT) has been associated with controlling wellbore instability caused by weak shale before reaching the reservoir. Due to limited availability of pad locations and complex well trajectories, operators are now forced to drill high angle wells through shale as compared to vertical or low angle wells in the past. This has resulted in a substantial increase in drilling complications in terms of controlling shale instability.Comprehensive geomechanical studies from various fields of Middle-East have helped to determine most plausible root causes of shale rock instability and to draw a holistic geomechanical approach to solve the problem. Shale samples (core and cuttings) were collected from multiple fields, and various types of lab tests were performed on these samples including XRD, XRF, chemical tests, rock mechanical tests etc. Geomechanical modeling and drilling analysis were performed to compare the drilling events to the shale characteristics in order to determine the mechanisms of rock failure. Chemoporoelastic and plane of weakness modeling techniques were also performed to understand some less-common failure mechanisms that were driving instability within these shales.It was noted from the analysis that not all shales behave in a similar fashion. A potential solution that may solve instability problem in a particular field/region might not be effective in the other field/region. Geomechanical analysis suggested that a range of shale instability mechanisms ranging from stress induced failures and planes of weakness to complex rock-fluid interaction were responsible for hole instability, and different mud and drilling parameters are required to keep the hole stable in different shales. Raising the mud weight exclusively during drilling of these shales with multiple failure mechanisms was found to be ineffective and potentially counter-productive. A customized solution along with real-time geomechanics monitoring can help to mitigate shale instability in drilling of high angle wells.A customized methodology for shale stability has been proposed in this paper based on integrated mechanical and chemical characteristics of most commonly encountered shales in the Middle East. This approach has helped to devise a comprehensive as well as practical approach to enhance drilling efficiency through shales in various fields in the region. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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