What is casing design in drilling?

The design of a casing program involves the selection of setting depths, casing sizes and grades of steel that will allow for the safe drilling and completion of a well to the desired producing configuration. Such a casing string is called a combination string.

How do you design a casing?

Casing program design is accomplished in three major steps:

1. Mud program is prepared.
2. The casing sizes and corresponding drill-bit sizes are determined.
3. The setting depths of individual casing strings are found.

What is casing in oilfield?

Casing is a series of steel pipes that are run into a drilled oil well to stabilize the well, keep contaminants and water out of the oil stream, and prevent oil from leaching into the groundwater. Casing is installed in layers, in sections of decreasing diameter that are joined together to form casing strings.

What is a casing design factor?

Many factors enter into the production casing design. These include the mud weights required to drill the well and balance the formation pressures, the fracture gradients, casing seat depths, casing sizes, the directional plan, the cement program and the temperature profiles.

How is casing setting depth determined?

Two main factors determine the depth of the casing shoe, namely, the fracture pressure and the pore pressure. A third factor is the lithology, because it is desirable to place the casing shoe in a competent shale section. Methods to predict fracture gradients for deeper wells already exist.

What is a casing program?

Casing Programs. Sometimes the well is drilled in stages called a casing program. Here, a well is drilled to a certain depth, cased and cemented, and then the well is drilled to a deeper depth, cased and cemented again, and so on. Each time the well is cased, a smaller diameter casing is used.

How do you calculate casing pressure?

[28] Pipe To Pull Before Well Starts To Flow (ft) = (Overbalance x (Casing Capacity – Metal Displ.)) / (Mud Gradient x Metal Displ.) [30] Pressure drop per foot tripping dry pipe = (OMD x 0.052 x Metal Displ.) / (Casing Capacity – Metal Displ.)

Where do we set casings during drilling?

Casing is a large diameter pipe that is assembled and inserted into a recently drilled section of a borehole. Similar to the bones of a spine protecting the spinal cord, casing is set inside the drilled borehole to protect and support the wellstream.

How is well casing installed?

Also known as setting pipe, casing a well involves running steel pipe down the inside of a recently drilled well. The small space between the casing and the untreated sides of the well is filled with cement to permanently set the casing in place.

Why design safety factors should be considered in the casing design?

Why we need a safety factor? We use API Casing Design Safety factors to allow for such uncertainties and to ensure that the rated performance of the casing is always greater than any expected loading. In other words, the casing strength is always downrated by a chosen safety factor value.

How are casing points determined?

What size well casing do I need?

The casing determines the size of the pump: 5″ and 6″ casing will accommodate a 4” submersible pump: 5 – 90 Gallons Per Minute (GPM) 8″ casing will accommodate a 6” submersible pump: 50 – 200 GPM. 10″ casing will accommodate an 8” submersible pump: 100 – 800 GPM.

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