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The most important mechanical properties of casing and tubing are burst strength, collapse resistance and tensile strength. These properties are necessary to determine the strength of the pipe and to design a casing string. If casing is subjected to internal pressure higher than external, it is said that casing is exposed to burst pressure loading. Burst pressure loading conditions occur during well control operations, casing pressure integrity tests, pumping operations, and production operations. The MIYP of the pipe body is determined by the internal yield pressure formula found in API Bull. This equation, commonly known as the Barlow equation, calculates the internal pressure at which the tangential (or hoop) stress at the inner wall of the pipe reaches the yield strength (YS) of the material.
Two forms of derivatized cellulose have been found useful in well-cementing applications. The usefulness of the two materials depends on their retardational character and thermal stability limits. This is commonly used at temperatures up to approximately 82 C (180 F) for fluid-loss control, and may be used at temperatures up to approximately 110 C (230 F) BHCT, depending on the co-additives used and slurry viscosity limitations. Above 110 C (230 F), HEC is not thermally stable. HEC is typically used at a concentration of 0.4 to 3.0% by weight of cement (BWOC), densities ranging from 16.0 to 11.0 lbm/gal, and temperatures ranging from 27 to 66 C (80 to 150 F) BHCT to achieve a fluid loss of less than 100 cm3 /30 min.
Remedial cementing is undertaken to correct issues with the primary cement job of a well. Remedial cementing requires as much technical, engineering, and operational experience, as primary cementing but is often done when wellbore conditions are unknown or out of control, and when wasted rig time and escalating costs have the potential to force poor decisions and high risk. Good planning and risk assessment is the key to successful remedial cementing. Squeeze cementing is a "correction" process that is usually only necessary to correct a problem in the wellbore. Most squeeze applications are unnecessary because they result from poor primary-cement-job evaluations or job diagnostics.
Use of several types of production logs in combination can provide important information, often quite cost effectively, for diagnosing a gas kick encountered during drilling. An example is discussed below. During the coring of a gas sand at 15,000 ft, a pressure kick occurred, gas pressure was then lost at the surface, and mud was added periodically to keep the drillpipe full. On the day after the gas kick, noise and temperature logs were recorded during the same run inside the drillpipe with the well static. These logs were run to identify the flow path of a likely underground blowout.
Production logging tools can provide important information for assessing a gas blowout after abandonment. A well was drilled through two gas zones on the way to test a deeper oil zone. The well was abandoned and the wellhead cut at the seafloor. Six months after abandonment, there was a gas blowout to the surface, causing the sea to churn. A relief well was drilled in order to flood the blowing zone.
The first fracture treatments were pumped just to see if a fracture could be created and if sand could be pumped into the fracture. In 1955, Howard and Fast published the first mathematical model that an engineer could use to design a fracture treatment. The Howard and Fast model assumed the fracture width was constant everywhere, allowing the engineer to compute fracture area on the basis of fracture fluid leakoff characteristics of the formation and the fracturing fluid. Modeling of fracture propagation has improved significantly with computing technology and a greater understanding of subsurface data. The Howard and Fast model was a 2D model.
Loss of circulation is the uncontrolled flow of whole mud into a formation, sometimes referred to as a "thief zone." This article discusses causes, prevention, and remedial measures for lost circulation. Figure 1 shows partial and total lost-circulation zones. In partial lost circulation, mud continues to flow to surface with some loss to the formation. Total lost circulation, however, occurs when all the mud flows into a formation with no return to surface.
Remedial cementing requires as much technical, engineering, and operational experience, as primary cementing but is often done when wellbore conditions are unknown or out of control, and when wasted rig time and escalating costs force poor decisions and high risk. Squeeze cementing is a "correction" process that is usually only necessary to correct a problem in the wellbore. Before using a squeeze application, a series of decisions must be made to determine (1) if a problem exists, (2) the magnitude of the problem, (3) if squeeze cementing will correct it, (4) the risk factors present, and (5) if economics will support it. Most squeeze applications are unnecessary because they result from poor primary-cement-job evaluations or job diagnostics. Squeeze cementing is a dehydration process.
As SPE's Distinguished Lecture series wraps up its SPE section presentations for 2020–2021, a new series of virtual presentations stretches through the summer, providing access for all SPE members. Three of the live virtual presenters will be speaking on topics in the health, safety, environment, and sustainability (HSES) discipline. Each year, SPE selects industry experts, nominated by their peers, to share their knowledge and expertise at SPE section meetings. Despite the many challenges faced this season, SPE's Distinguished Lecturers gave more than 450 virtual presentations to members in more than 191 SPE sections countries around the world. Starting on 22 June, 22 presentations will be made available live virtually, broadening the audience from SPE section meetings to all of SPE's membership.