Comparing Injection Pressures
SITE
Former D&A Produce (Active Retail and Pharmacy Store), Chipley, FL
CONTAMINATION
Gasoline Range Organics in ground water
BACKGROUND
A release of gasoline fuel from a UST at this facility led to soil and groundwater contamination. The tanks were removed and after proper site assessment and a pilot test it was decided to move forward with a combination of the Vertebrae Well System and traditional vertical wells. An automated injection system was used (EN RX Support Platform) which allows pressure readings to be recorded throughout the injection process. These can be used to compare the performance of the Vertebrae and vertical well
segments.
SITE LITHOLOGY
The lithology has been described as silty clayey sand from 5-10’ bls, cohesive clay from 10-12’ bls, sandy clay from 12-22.5’ bls, and cohesive clay with sand seams from 22.5-37.5’ bls.
WELL DATA
- The 4 Vertebrae Well Systems are installed between 11-14’ bls consisting of 11 well segments total.
- The intermediate vertical wells are at 17.5-22.5’ bls.
- The deep vertical wells are installed at 27.5-32.5’ bls.
- Figure 1 shows the well layout with all wells trenched to the injection system compound.
- When connecting to the 18 channel system the wells were teed together to inject into all 41 segments.
Figure 1: D&A Produce Injection Well Array
RESULTS
The table below includes three readings of the average pressure measured of each injection channel. The injection system automates injection into each channel for the same time per cycle (2 mins per channel) and the same flow rate, 0.5 gpm. The Vertebrae well segments experienced on average a pressure of 2.1 psi during injection events. This is much lower when compared with the intermediate vertical wells (average of 10 psi) that were installed in a similar lithology. The deep vertical wells performed with an average pressure of 12.9 psi showing a correlation with the difficulty of injecting into a clay lithology.
CONCLUSION
It is difficult at most sites to compare these two types of wells as it is rare to install them for the same purposes, at the same depths, and in similar locations. However, this site presented this unique opportunity, and the outcome was impressive. The Vertebrae well systems appear to perform 4 to 5 times better (based on pressure) than the vertical wells in the same lithology at similar depths and with the same amount of well screen. Higher flows are likely possible using the Vertebrae well segments, and it is more likely that lower pressure results in a more even injection. This site provides proof of what models
show, that horizontal applications provide better contact to the subsurface and result in higher performance.
