Reservoir simulation

It’s Possible That Salt Clogging Is Lowering Your Gas Production

A new program offers an affordable way to figure out if salt precipitation could be behind underperforming gas wells and suggests a path to higher production.

detail of crystal salt
Getty Images.
Charts a, b, c, d compare gas production, bottomhole pressure, and oil and water production
Fig. 1—Charts a, b, c, d compare gas production, bottomhole pressure, and oil and water production as modeled with salt blockages (solid line) and without (dotted line).
Source: SPE 212257.

Salt buildup around producing wells is known for causing drastic drops in gas production.

“Salt precipitation in gas wells (can) cause clogging, and severe production declines that may happen in days,” said Cíntia Gonçalves Machado, a scientist at TNO, which supports operators working in the waters off the Netherlands where salt blockages are a significant issue for producers.

She recently presented a paper at the SPE Reservoir Simulation Conference on a new application that cuts the time and cost required to analyze the impact of salt on production and evaluate treatment plans (SPE 212257).

The goal for TNO and its partner, Equinor, was to create an open-source simulator built on to a familiar engineering tool allowing “engineers to study how salt precipitation may affect production with a tool that is relatively cheap computationally, and also easy to use and visualize,” Machado wrote in an email.

Specifically, the team that developed it started with a black-oil model in the open-source OPM Flow simulator and added elements that simulate salt precipitation, which happens as rapidly evaporating gas pulls water molecules out of salty brine, and estimate the effect on permeability.

Other programs can do all that. What makes this one different is that it can run on an engineer’s laptop and can run a simulation in minutes to hours, while previous models require high-powered computer systems running for hours to days, Machado said.

The early users are likely to be the small cadre of experts working on the extreme cases where salt buildup happens so rapidly that regular injections of fresh water are needed to dissolve the blockages. But Equinor also wanted a tool to help it identify wells where salt blockages are having a slower-building impact that is not obvious.

“They see wells with a reduction in gas production and want to have some tool to understand and predict it,” said Paul Egberts, a staff mathematician at TNO who applied his years of salt-modeling experience to this project.

The team also included Odd Steve Hustad, a reservoir technology specialist at Equinor who advised on how to accurately incorporate the physical properties of the brine into the black‑oil model.

The paper described their work: “The black-oil transport equations are extended to allow the gas to contain vaporized water in addition to vaporized oil. The salt-transport equation is modified to account for a solid salt precipitate.

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