Multi-Channel (MCS) Production Tubing was
specifically designed for wells that have liquid loading problems. As gas wells deplete, reservoir pressure declines, and gas velocity up the well decreases. Even though the gas-liquid ratio entering the wellbore may be unchanged, sooner or later, liquid eventually starts to collect in the wellbore because the gas velocity becomes insufficient to carry the liquid out of the well.
In a sense,
MCS production tubing is a re-invention of the velocity string. They are similar in theory (reducing tubing diameter to regain steady state flow)... but an MCS greatly extends the timespan of its benefits (maintaining steady state flow) and fixes its main drawbacks (lower gas production rate and difficulty in kicking off).
An MCS is a new type of "production tubing" that
divides the flow up the well into multiple flows through small-diameter internal passageways. By reducing the diameter of each individual flow passageway, it reduces the "Turner Critical Rate" (i.e., minimum gas flowrate/ velocity) required to maintain steady state flow up the well (see "Turner Critical Rate" page)... and by utilizing multiple flow passageways, it compensates for the restrictive/ choking effects of using a single small-diameter passageway.
For example, for 2-inch ID tubing, the gas velocity up a well flowing at the "Turner Critical Rate" is > 20 feet per second.
tubing (e.g., as pictured above, with seven 7mm-diameter internal passageways)
will flow at steady state down to a gas velocity of as low
as 2 fps, assuming the same gas-liquid ratio. Ultimate recovery is greatly increased, and without the costs and complexities of artificial lift.
Two designs of MCS production tubing are available from stock, shipped from Canton, Ohio. Both are intended for
conventional gas wells producing under 50 Mcf per day, having a well depth of under 5,000 feet.
One has a gas flow range of 8 to 40 Mcfd (1 1/4 inches in diameter, priced at $1.75 per foot), and the other from 2 to 12 Mcfd (1 inch diameter, priced at $1.35 per foot).
In the near future, other MCS production tubing designs will be available, such as those accomodating gas production volumes of up to 1 MMcfd or more, and those with greater tensile strength to permit deployment in wells up to 9,000 feet deep.
MCS production tubing requires no maintenance, no consumables, and no outside energy input. Kickoff is automatic (no swabbing). Particulates are produced along with the liquid, and the extrusion polymer is resistant to the buildup of salt, scale and paraffin.