Which Gas Processing Equipment should I use?
Although there are many options for processing midstream gas, no one option is best for all circumstances. The major driving forces when choosing the correct processing method are gas composition, residue specifications, NGL takeaway, and the expected long-term inlet gas volume and composition projections. In many cases, the best answer ends up being multiple processing options that change over time as the field develops and then matures due to inlet volume and composition fluctuations.
The amount of NGL liquids in the gas is typically a major consideration in choosing the processing methodology. A leaner liquid gas composition will favor choosing a JT unit or refrigeration process. JT units are very economical when the required compression is currently available on-site. Rich gas compositions and large processing volumes will favor cryogenic processes when an NGL sales line is available to the processing site.
The residue gas pipeline can dictate the processing method if it has a stringent BTU or GPM specification. The chosen processing method must meet the residue pipeline gas specifications.
Will you sell NGLs to a pipeline, put them in a truck, or weather them in an atmospheric tank? You must know what your NGL market is before you can choose a processing technology. What are the required specifications for the NGLs? How much will it cost to get the NGLs to market? With this information, you can then determine the profitability of the different gas processing options for your application.
Do you expect your well/field to have a quick or slow decline? Do you expect to add more wells or find new gas streams to add to the plant? Do you want your equipment to be able to change NGL recoveries based on market conditions? These questions help determine whether a large capital plant is best upfront or leased equipment should be used to hedge against changing gas volumes and market economic conditions.
Gas Processing Options
JT plants are simple setups that use a pressure drop to cool the gas to meet a dew point specification. For more information on how they work, please visit the page on our JT Units. If you have enough available free pressure drop and a lean gas, JT units are usually the best choice because there is so little cost to operate them—no utilities, minimum operator attention, or major maintenance. JT units can run in a field for years with a pumper coming by only several times a day to manage them. JT units work especially well on dry gas and when the consumed pressure drop is economically free to the producer, making them ideal for gas storage fields.
Electric Refrigeration Plants
If there is no pressure drop or the gas is too rich, a good solution may be an electric refrigeration plant, which cools the gas using electric refrigeration, just like the air is cooled in your home or office. Electric refrigeration is easy to operate, easy to install when skidded, and can be deployed quickly. The lowest temperature that can be achieved is usually –15 °F, so if your specifications require a colder temperature, then you will need to add a JT valve with some pressure drop or move to propane refrigeration or cryogenic. Click here to learn more about our leased electric refrigeration.
Propane Refrigeration Plants
They are good options for longer-term solutions with steady inlet flow volumes that require processing temperatures in the –10 to –35 °F range. Propane refrigeration uses propane as the refrigerant, allowing temperatures as low as –40 °F. Propane refrigeration requires more extensive installation, including foundations for a large compressor and more extensive monitoring and maintenance. However, a propane refrigeration process can be gas powered instead of electric. Dew Point Control does not offer propane refrigeration.
If you want the absolute best product recoveries, then we recommend a cryogenic plant. A cryogenic plant is usually based around a turbo-expander, when the inlet gas is rich in NGL liquids. Then supplemental refrigeration must be added upstream of the expander to achieve temperatures well below –80 °F. These plants are time consuming to build, and expensive to install and operate but are often the best choice for long-term profits. Dew Point Control does not offer cryogenic plants, but our leased JT and refrigeration units are often used to bridge the time required to build or expand an existing cryo unit or to debottleneck an existing cryogenic plant by leaning up the inlet gas stream with supplemental refrigeration.
Multiple Processing Scenario
DPC was fortunate to be involved with the development of the gathering and processing of the first Marcellus rich gas area near Houston, PA. The original producer contacted DPC and leased several of our large JT units and some NGL tanks so they could flow their original Marcellus wells to market. The JT units removed enough liquids so that the gas would meet the HCDP requirements of the takeaway residue pipeline. The virgin reservoir was still at high pressure, and the use of JT units was the most economical way to process the gas at the production sites.
Once the reservoir was proven, the midstream processor moved in to gather the area’s production and install the long-term processing and gathering facilities. The high liquid content of the gas made the gathering and processing very important and justified cryogenic processing. Having previously worked for the processor at several other locations, DPC was asked to supply a 40 MMSCFD refrigeration unit including NGL stabilization and tankage. This unit’s purpose was to handle the interim production until the processor could get its permanent cryogenic plant installed and operating. In reality our facilities stayed in place much longer than expected. The processor ended up moving in a used 50 MMSCFD expander plant from south Texas, and followed that with a new 200 MMSCFD expander plant, and then another new 200 MMSCFD expander plant. Once all this equipment was up and lined out, our 40 MMSCFD unit was sent home.