a single well that produces from two separate formation at the same time. Production from each zone is segregated by running two tubing strings with packers inside the single string of production casing, or by running one tubing string with a packer through one zone while the other is produced through the annulus. In a miniaturized dual completion, two separate 4 1/2-inch or smaller casing strings are run and cemented in the same wellbore.

Related Terms

• Multiple Completion

an arrangement for producing a well in which one wellbore penetrates two or more petroleum-bearing formations. In one type, multiple tubing strings are suspended side by side in the production casing string, each a different length and each packed to prevent the commingling of different reservoir fluids. Each reservoir is then produced through its own...

• Side-By-Side Completion

a single bore-hole completion where there are distinct surface-to-zone tubing strings with isolation from each other....

• Tubingless Completion

a method of producing a well in which only production casing is set through the pay zone, with no tubing or inner production string used to bring formation fluids to the surface. This type of completion has its best application in low-pressure, dry-gas reservoirs....

• Slim-hole Drilling

drilling in which the size of the hole is smaller than the conventional hole diameter for a given depth. This decrease in hole size enables the operator to run smaller casing, thereby lessening the cost of completion. See miniaturized completion....

• Casinghead

a heavy, flanged steel fitting connected to the first string of casing. It provides a housing for slips and packing assemblies, allows suspension of intermediate and production strings of casing, and supplies the means for the annulus to be sealed off. Also called a spool....