What are the most effective well casing design practices for drilling?

1 Casing Types and Functions

The first step in well casing design is to select the appropriate types and functions of the casings for your well. Generally, there are four main types of casings: conductor, surface, intermediate, and production. Each type has a specific function and role in the well construction process. For example, the conductor casing is the first and shallowest casing that is installed to prevent the collapse of the loose soil near the surface. The surface casing is the second casing that is installed to isolate the freshwater zones and provide a base for the blowout preventer. The intermediate casing is the third casing that is installed to seal off any troublesome formations and provide pressure control. The production casing is the final and deepest casing that is installed to isolate the production zone and enable the flow of fluids to the surface.

2 Casing Design Criteria

The second step in well casing design is to determine the design criteria for each casing section. The design criteria are the parameters that define the performance and safety requirements of the casings, such as burst, collapse, and tensile strength, as well as corrosion resistance, thermal expansion, and fatigue. The design criteria are influenced by the well conditions, such as depth, pressure, temperature, fluid properties, and formation characteristics. To calculate the design criteria, you need to use various methods and tools, such as empirical formulas, analytical models, numerical simulations, and software applications.

3 Casing Connections and Accessories

The third step in well casing design is to choose the appropriate connections and accessories for the casings. The connections are the joints that connect the casing segments together, and they can be either threaded or welded. The accessories are the additional components that are attached to the casings, such as centralizers, float shoes, float collars, cementing baskets, and stage collars. The connections and accessories affect the installation, integrity, and performance of the casings, as they provide sealing, alignment, anchoring, and cementing functions. To select the optimal connections and accessories, you need to consider factors such as load capacity, reliability, compatibility, and cost.

4 Casing Running and Cementing

The fourth step in well casing design is to plan and execute the casing running and cementing operations. The casing running is the process of lowering and inserting the casings into the borehole, and it requires careful coordination, monitoring, and control. The casing cementing is the process of pumping cement slurry into the annulus between the casings and the borehole wall, and it requires proper mixing, displacement, and placement. The casing running and cementing operations are critical for ensuring the stability, isolation, and integrity of the casings, as they prevent leakage, migration, and contamination of fluids.

5 Casing Evaluation and Testing

The fifth step in well casing design is to evaluate and test the casings after they are installed and cemented. The casing evaluation is the process of inspecting and verifying the condition and quality of the casings, and it involves various methods and techniques, such as logging, caliper, and ultrasonic. The casing testing is the process of applying pressure and temperature to the casings, and it involves various equipment and procedures, such as packers, gauges, and valves. The casing evaluation and testing operations are essential for confirming the performance and safety of the casings, as they detect and resolve any defects, damages, or failures.

6 Casing Maintenance and Repair

The sixth and final step in well casing design is to maintain and repair the casings throughout the well life cycle. The casing maintenance is the process of monitoring and preventing any deterioration or degradation of the casings, and it involves various actions and measures, such as corrosion inhibition, scale removal, and biocide injection. The casing repair is the process of restoring and improving any compromised or impaired casings, and it involves various solutions and options, such as patches, liners, and squeeze cementing. The casing maintenance and repair operations are vital for extending the longevity and functionality of the casings, as they enhance the well integrity, productivity, and profitability.

7 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?