[Editor’s note: This story appears in the June 2020 edition of E&P. Subscribe to the magazine here. It was originally published May 27, 2020.]

A perfect storm of too low oil prices, too low demand and too much supply forced many operators to make the difficult decision to shut in production. IHS Markit announced in May that it expected as much as 17 MMbbl/d total liquids output (which includes nearly 14 MMbbl/d of crude oil production) to be cut or shut in between April and June.

The process of shutting in production is more complicated than simply flipping a switch. Physical challenges, like paraffin blockages and microbial-induced corrosion, could be effectively managed by “pickling” the well.

Pickling is preserving something for an extended time. Think summer-fresh cucumbers cleaned and preserved in a briny solution to keep from spoiling to enjoy on a wintry cold day. Pickling also is the process of using acid to remove foreign substances from metal. When a well is pickled, the wellbore is cleaned and treated with paraffin inhibitors and biocides to save downhole components and its production for better days and higher oil prices.

“The state of the well is preserved when shut in,” Willem Marais, technical service manager for M-I SWACO, a Schlumberger company, told E&P. “When favorable conditions return, the well can be started up in a condition similar to when it was before shut-in.”

It is a time-proven process, and its application in the unconventional wells of today demonstrate how the industry is applying the lessons learned over the years.

“In heritage fields or ones with high water cuts and significant lifting costs impacting opex, historically they’ve been shut in to prevent losing money on the wells,” Jimmy Ott, technical support manager of oilfield and industrial chemicals with Baker Hughes, told E&P. “We’ve been through market downturns a number of times. We’re using our past experiences to ensure operators understand the value of preserving their downhole and surface facility assets.”

Controlling the integrity of the well, along with ensuring a smooth restart with production volumes at pre-shut-in levels, are the primary reasons to perform a pickling treatment, Marais noted.

“In producing wells, the fluids are constantly moving,” he said. “But when it is shut in, a stagnant environment is created.” 

Hot fluids flowing through the wellbore and out to associated flowlines keep the system warm. Shutting in the well reduces or eliminates the heat distribution, causing the system to cool down.

“The worst-case scenario is when there are hydrocarbons in the tubing or in the well that begin to precipitate organic components like the waxes or asphaltenes, potentially creating a blockage in the system that will inhibit flow when the well is restarted,” Marais said. “It will require a capex spend to remove and clean out the blockages before the well can produce again.”

Microbial-induced corrosion is another well challenge. While microscopic in size, its impact is significant in that it is destructive to the wellbore and associated equipment, according to Ott.

“Bacteria begin to feed on the nutrients found in the stagnant fluids and begin to proliferate, with the result being incredibly damaging corrosion. In the Permian Basin, for example, the sulfate-rich waters provide plenty of nutrients for sulfate-reducing bacteria to grow and rapidly damage equipment.”

In 1736 Benjamin Franklin coined the phrase, “An ounce of prevention is worth a pound of cure.” In today’s rapidly changing oil markets and operating dynamics, there is a truth there in that “an ounce of preservation today is worth a pound of headaches later.”

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