Water Disposal Simulation

When hydrocarbons are extracted from the subsurface, they come up as a mixture of oil, gas, and water. Through various processes this mixture is separated into its constituent streams with the oil & gas being sold or sent to a refinery for further processing. The produced water typically contains too many contaminants (such as asphalts, paraffins, chlorides, NORM, etc.) that it isn't practical to treat it for potable or non-potable applications. Instead, old wells that have already depleted their reservoirs are converted into water disposal wells where the produced water can be safely disposed of by injecting it into the now vacant pore space.

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Even though most of the oil is separated out upstream of the salt water disposal facility (SWD), small amounts still remain mixed in with the water. Before the water is injected, it passes through a final separate tank called a "Gun Barrel" that uses gravity separation to split the two phases. The less dense oil is skimmed from the top of the tank while the denser water is pulled from the bottom. The height of the oil-water interface is determined by the relative densities of the two liquids and an upside-down U-shaped bend in the water takeaway line called a "water leg" that provides hydrostatic backpressure into the gun barrel. Sizing the height and diameter of the water leg is critical to the facility functioning correctly. If the water leg is too low, it won't provide enough back pressure to hold the oil-water interface above the water takeaway line and oil will be pulled through the facility to be re-injected back underground, resulting in a loss of revenue. If the water leg is too high, water will be pulled into the oil skim tanks and mix with the hydrocarbons, which would then require additional processing before being sold.

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At the start of the project, the company was struggling with the water legs at their facilities being too low, meaning the oil wasn't being skimmed off the top of the gun barrel correctly and was instead being injected into the disposal well. Since multiple new facilities were scoped to be built in the near future, each having a different set of design requirements (such as daily water throughput), rather than developing a single set of recommendations to work under one set of operating conditions, I built a water disposal simulator that modeled the fluid levels in the gun barrel based on user specified inputs. This tool could then be used to optimize the design of any future SWD facility regardless of the design constraints.

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Please click through the gallery below to learn more about the project. Hovering over an image/video will provide a brief summary of what you're looking at and clicking on it provide a more detailed description.