API Publ 4758:2006 pdf download
API Publ 4758:2006 pdf download.Strategies for Addressing Salt Impacts of Produced Water Releases to Plants,Soil, and Groundwater.
Using the Planning Model
Results of this modeling are combined with other site-specific information to determine the potential eliects on groundwater.
To use the Planning Model, perform the blowing steps:
Step 1: Estimate Mass of Chloride using volume and chloride concentration of a produced water release, OR
Estimate Mass of Chloride using the area of produced water release (area of affected soil) and the chloride concentration of the soil (page 10>
Step 2: Estimate Chloride Loadirio Rate to Groundwater using me Annual Precipitation, (page 11)
Step 3A: Estimate increase ki Chloride Concentration In Groundwater at the Release Point using the width of the release area. (page 12)
Step 3B: Refine the estimate Iron, Step 3A using site-specific information (either the site location, or more detailed hydrogeologic info). (page 13)
Step 4: (Optional) Estimate the Increase in Chloride Concentration in Groundwater at a Downarac*ent Point using the distance from the release area (and other parameters). (page 14)
Key assumptions and limitations of the Planning Model include: 1) salts are mixed evenly throughout the soIl; 2) the percentage of the rainfall that infiltrates through the soil to groundwater is proportional to the amount of rainfall; 3) (tie recharge rate is the 80” percentile of recharge rates from data compiled from API Publication 4643: 4) almost all the salts in affected sells can be flushed out with 12 inches of recharge (from API 4663): 5) no capillary effects, evaporation, or other transport processes except advection. mixing. and dispersion in the saturated zone are present: 6) no density effects are assumed in transport of chloride In groundwater: 7) salt is mixed throughout the water-bearing unit: 8) a 2x safety factor is assumed: arid 9) potential impacts only apply to the uppermost water-bearing unit, and NOT to deeper, regional aquifers. When applied to site conditions presented in API Piication 4734, the Planning Model was more liely to show higher chloride concentrations in groundwater than chloride concentrations predicted by HYDRUS, a much more sophisticated leaching model.
Other Methods
Other approaches can also be used to provide more accurate estimates of chloride migration. Key resources include:
• API Publication 4734: In this study, the authors performed several hundred computer simulations with the HYDRUS model to determine the sensitivity of groundwater undertying a produced water release to various factors such as release volume, chloride concentration of the produced water, depth to groundwater. soil type, rainfall and hydrology of the area, and other factors, Review of this document can provide additional information regarding the impact of produced water releases on groundwater.
• More Detailed Computer Models: Models such as VADSAT or HYDRUS can be applied to investigate potential groundwater impacts from produced water releases.
• Site Investigation: A groundwater site investigation Involving the collection of groundwater samples from monitoring wells or direct push sampling techniques can show if a produced water release has actually aliected groundwater at a given site.
Factors That May Influence Rernedlatlon of Saltwater Releases
For the purposes of this guide, the principal obfective of groundwater remediation is to maintain the beneficial use of the groundwater resource. However. remediation of saltwafer releases can be influenced by a variety of non-technical factors that are not directly addressed in this guide. These non-technical factors include (API Puolication 4663):
How Does Produced Water Quality Vary Across The U.S.?
This map from the U.S. Geological Survey (Breit and Otton, 2002) based on almost 60,000 produced water analyses taken across the
country, shows the Total Dissolved Solids (TDS) content to vary significantly among the various oil and gas regions of the U.S. Such
variations are explained by the age, geochemistry, and hydrology of the specific formation(s) from which the water comes. In the
Powder River Basin of Wyoming, gas production zones can yield produced water with a TDS < 1000 mg/L, corresponding to freshwater, while in some areas of Oklahoma and West Texas, the TDS content can exceed 200,000 mg/L, corresponding to strong brine.
