How do you design and optimize well trajectories and casing programs to enhance well bore stability?

1 Well trajectory design

Designing a well trajectory that enhances well bore stability requires careful consideration of the orientation and magnitude of rock stresses, the rock properties, the drilling fluid properties, and the well bore deviation tools. Software tools such as well planning software, geomechanical models, and directional drilling simulators can be used to design and evaluate different well trajectory options and optimize them based on well bore stability criteria. This will help you minimize drilling costs, maximize reservoir contact, avoid geological hazards, and comply with environmental regulations.

2 Casing program design

The casing program is an essential sequence of casing strings installed in the well bore to support the well structure, isolate different formations, and control the well pressure. When designing a casing program , you must consider factors such as the well load scenarios, pressure profiles, temperature profiles, and corrosion risks. These all affect the casing stresses, strains, burst loads, collapse loads, axial loads, thermal expansion and contraction, material selection, and corrosion protection. Software tools like casing design software, stress analysis models, and casing wear simulators can be used to design and evaluate different casing program options and optimize them based on well bore stability criteria.

3 Well bore stability analysis

Well bore stability analysis is the process of assessing the risk of well bore failure and identifying the optimal well pressure and well geometry to prevent or mitigate it. This type of failure can occur in different modes, such as tensile, shear, compaction, and sand production. The analysis involves collecting and quality controlling data, such as logging, core, drilling, and test data to create a geomechanical model. This model is used to evaluate the likelihood and severity of well bore failure for different scenarios with criteria, indicators, and sensitivity analysis. Finally, you can use software tools to optimize your well design with mud weight optimization, trajectory optimization, and casing optimization.

4 Well bore stability monitoring

Well bore stability monitoring is the process of observing and measuring the actual well bore conditions and comparing them with the predicted ones. This can help detect and diagnose issues such as instability, lost circulation, stuck pipe, formation damage, and casing deformation. Well bore stability monitoring typically involves drilling performance monitoring (e.g. rate of penetration, torque and drag, vibration, bit wear) to indicate drilling efficiency and well bore friction; drilling fluid monitoring (e.g. mud weight, rheology, filtrate loss, cuttings analysis) to indicate well pressure and formation interaction; well logging monitoring (e.g. caliper logs, image logs, sonic logs, density logs) to indicate well bore geometry and rock properties; and well testing monitoring (e.g. pressure tests, leak-off tests, formation integrity tests, injection tests) to indicate well pressure limits and rock strength. Software tools such as real-time data acquisition systems, data visualization tools, and data analysis tools can be used to monitor well bore stability and adjust drilling parameters accordingly.

5 Well bore stability challenges

Well bore stability challenges can significantly increase the complexity and difficulty of maintaining well bore stability. These challenges may vary depending on the geological setting, the reservoir characteristics, and the drilling objectives. For example, high-pressure high-temperature wells require special casing materials, drilling fluids, and operational procedures to withstand extreme conditions. Shale wells are prone to hydration, swelling, creep, and collapse due to the complex mineralogy and anisotropy of shale formations. Horizontal wells have higher dogleg severity, torque and drag, and buckling risks due to the long lateral sections and the high inclination angles. Multilateral wells have higher stress concentration, fracture initiation, and casing connection failures due to the multiple branches and junctions. Extended reach wells have higher frictional pressure losses, hole cleaning issues, and well control difficulties due to the large horizontal displacements and depths. To overcome these well bore stability challenges and optimize well performance, advanced geomechanical models, directional drilling simulators, and multilateral design software can be used.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?