Bulletin No. 64


depending on the degree of dolomitization. The interval is generally well indurated (Appendix A7). From 1,840 to 1,980 feet BLS the dominant lithologies are interbedded wackestones and packstones with 10 percent to 25 percent porosity and moderate induration. No permeability estimates are available for this interval.

 Background water-quality data (CH2M Hill, 1986), taken while the well was being drilled, show a chloride value of approximately 3,500 mg/L at the level of the lower monitor zone. A packer test at the interval from 1,426 to 1,436 feet BLS in the lower monitor zone, shows an average TDS value of 10,150 mg/L. The 10,000 mg/L TDS boundary in this area occurs at approximately 1,450 feet BLS.

 Injection at this site started in November 1986. Lower monitor zone water-quality data show a slight increase in TDS from 2,000 mg/L in mid1989, when TDS data were first collected, to 5,000 mg/L in early 1991. There is then a jump to over 11,000 mg/L by mid-1991. Note that the initial TDS values taken in 1989 are markedly lower than the background value of 10,150 mg/L taken in 1986. Water in the monitor zone could have experienced freshening between 1986 and 1989, before the increase in salinity in 1989 to 1991. More likely, the background value is erroneous because it was taken during drilling when ambient conditions would have been disrupted.

 Chloride values hold steady around 1,000 mg/L from late-1986 to mid-1989, and then increase to 5,000 mg/L by mid-1991. The initial Florida DER values are again lower than the background readings. However, the increase in chloride concentrations from mid-1989 to 1991 does correspond to the increase in TDS values, indicating that saline formation water is being displaced upwards by injected water.

 Hercules, Inc.

 The Hercules injection well has a total depth of 3,005 feet BLS in the Oldsmar Formation.


The confining interval, defined by CH2M Hill (1979), is from 1,500 to 2,400 feet BLS in the lower Avon Park and upper Oldsmar Formations. The main injection zone extends from 2,378 to 2,930 feet BLS in the Oldsmar Formation (Appendix A8). There is a separate multizone monitor well with four zones: 1) the upper Floridan, from 466 to 591 feet BLS in the Ocala Limestone, 2) the middle Floridan, from 880 to 931 feet BLS in the upper Avon Park Formation, 3) the lower Floridan, from 1,387 to 1,451 feet BLS in the middle Avon Park Formation, and 4) the primary, extending from 1,905 to 1,963 feet BLS in the lower Avon Park Formation.

 The confining zone, as defined by CH2M Hill, from 1,500 to 1,900 feet BLS is primarily packstone, with a few interbedded dolostone layers. The porosity of this section ranges from 20 to 35 percent. The section is generally moderately indurated, and permeability is estimated to be high. From 1,900 to 2,300 feet BLS dolostone dominates, with scattered wackestone and packstone interbeds. Porosity ranges between two percent and 10 percent in the dolostone, and between 15 percent and 25 percent in the interbeds. The section is well indurated and appears to have low permeability. From 2,300 to 2,400 feet BLS wackestones and packstones of 20 percent to 25 percent porosity, moderate induration and medium permeability dominate.

 Background water-quality data show that in the primary monitor zone the chloride concentration was 17,350 mg/L, and in the lower Floridan monitor zone it was 4,490 mg/L. A packer test in the interval from 1,949 to 1,959 feet BLS in the primary monitor zone showed values of 17,600 mg/L for chloride, and 28,200 mg/L for TDS.

 Injection at the site started in November 1979. However, collection of data on TDS and TKN for the primary monitor zone didn't begin until 1990. and no patterns are discernible. Chloride concentration data fluctuates between 17,000 and