High-Integrity Casing Strings From End to End

Mention high integrity casing strings, and one thinks of gas-tight connections, and that is an important part of the story. However, complex well-bore geometrics; hot, high-pressure and unstable holes; complex re-entries; and a host of other considerations are creating integrity demands that go beyond the connection.

As a result, ensuring casing-string integrity has become a holistic enterprise focused on system performance from one end of the string to the other. This emphasis takes many forms to ensure that a high-integrity casing string reaches the target depth with the designed diameter and, once in place, provides an effective wellbore over the life of the well.

Drilling-with-casing and solid expandable liner technologies are integral to reaching target depth with the optimal hole size. Advanced torque-monitoring technologies provide quality assurance during makeup and while running the casing. Zonal isolation is ensured with cementing equipment from swellable centralizers to float and stage devices. Cement-bonded logging tools—including the conventional ultrasonic radial scanner—provide access and performance that plays a vital role in verifying the installation of a high-integrity casing string.

Three service examples—torque monitoring, drilling-with-casing and solid expandable liner—illustrate the scope of this advance.

Torque Monitoring

Torque monitoring ensures that proper connection makeup is the quintessential focus for high-integrity casing strings. However, technology advances have extended torque monitoring to the stress condition of the entire string.

For example, in tight-radius, shale-gas wells, the high build rate in the curve section puts additional stress on the casing string during installation. In many cases, rotation and reciprocation during running is required to reach TD, including stresses into the casing and connections. Concerns about connection integrity during subsequent fracturing simulation work have added monitoring of down-hole torque and string weight to the traditional focus on rig-floor connection makeup.

A top-drive casing-running and drilling system can provide significant advantages in ensuring casing-string integrity. Some systems that include an electronic load cell can provide highly accurate and fast-response torque and weight measurements that are much more reliable than the rig’s top-drive readings. This capability is a major factor in the system’s success in drilling tight-radius well geometrics.