NB/T 11621.1-2024 in English
VALIDShale Gas Core Logging Technology Specification Part 1: Core Acquisition Operations
- Issued on:2024-09-24
- Implemented on:2025-03-24
- File Format:PDF
- Delivery:Via email within 2~4 business days
$329.00
| Standard No: | NB/T 11621.1-2024 |
| Document status: | VALID |
| Title in English: | Shale Gas Core Logging Technology Specification Part 1: Core Acquisition Operations |
| Title in Chinese: | 页岩气 保压取心技术规范 第1部分：取心作业 |
| Language: | English |
| File Format: | Electronic (PDF) |
| Delivery: | Via email within 2~4 business days |
| Issued on: | 2024-09-24 |
| Implemented on: | 2025-03-24 |
| Chinese Classification: | E13-Petroleum drilling |
| Professional Classification: | NB-Energy |
| Related Keywords: | shale gas core logging technology specification part
shale gas pressure-maintaining coring shale gas deep shale gas exploration core acquisition operations introduction technical background |
Introduction
Technical background and innovative value of the standard
As my country's first special standard for shale gas pressure-maintaining coring, NB/T 11621.1-2024 fills the gap in technical standards for deep shale gas exploration. Compared with conventional coring standards such as SY/T 5347-2016, its core innovations are reflected in:
| Comparison dimensions | Traditional coring standards | Pressure-maintaining coring standards |
|---|---|---|
| Pressure maintenance | No clear requirements | Requires 15MPa stable pressure for 10min and pressure drop ≤0.5MPa |
| Seal detection | Visual inspection | Soap water detection + pressure decay double verification |
| Tool configuration | Basic coring tools | Mandatory equipment class=instrument>Differential assembly and Pressure-maintaining inner tube sealing valve |
Analysis of key operation technical requirements
1. Tool sealing verification
Article 5.3.4 of the standard clearly requires a step-by-step pressure test: 1MPa initial inspection + 15MPa final inspection. Compared with the API standard, an intermediate pressure transition link is added to detect seal assembly defects in advance.
2. Wellbore adaptability design
Differentiated drilling tool combination solutions are given for different well types, and it is particularly stipulated that high-angle wells need to use ≤9m short tools, and horizontal wells need to adjust the position of the weighted drill pipe to solve the passability problem of conventional coring tools in complex wellbores.
Gas content test operation specifications
Typical case: During pressure-maintaining coring at the 2300m well section of a shale gas well, the pressure-maintaining inner tube was tilted 50cm according to the requirements of Article 7.2.3 and then tested. The measured gas content was 18% higher than that of the conventional method, confirming that the free gas content in the reservoir was underestimated.
Dual indicators for sealing verification
- Visual inspection: no bubbles in soapy water for 5 minutes
- Pressure decay: pressure drop <5% in 15-20 minutes
Implement risk control on site
According to Article 6.4 of the standard, a three-level termination mechanism needs to be established:
| Primary risk | Core blockage/core grinding | Immediately stop operation |
| Secondary risk | Abnormal fluctuation of pump pressure | Check the status of the sealing valve |
Suggestions on the direction of standard evolution
The next step needs to be supplemented: ①Correction coefficient of coring parameters for ultra-deep layers (＞3500m) ②Special treatment process for CO2-bearing strata ③Digital core tracing system interface specifications.
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