Purpose

The analysis of existing core samples represents an early-phase task authorized by the regional ASR Project Management Team. This effort is designed to characterize the lithology, stratigraphy, pore systems, and estimated permeability of the Upper Floridan Aquifer in the Lake Okeechobee area with the aim of predicting zones of preferred flow with the aquifer. Relating rock properties derived from core analysis to borehole geophysical log data in specific wells can serve as a comparative guide to the geology in nearby non-cored wells.

Background

Core analysis is a tool used in subsurface geologic exploration/exploitation and in the characterization of carbonate aquifers. Some of the parameters that can be obtained through core analysis include porosity, relative permeability, and lithology. The slabbing of core samples is a laboratory procedure used to enhance detailed descriptions of lithologic, paleontologic, and mineralogic information that is obscured by the rough outer core surface. Proper analysis of carbonate core material is difficult and time-consuming and requires the experience and skill of an expert carbonate rock geologist who is familiar with the hydrogeologic parameters encountered in diffuse carbonate and conduit flow systems such as the Upper Floridan aquifer.

Scope of Work

The proposed scope of work is divided into several phases: (1) collection of existing core samples and slab preparation of core samples, (2) lithologic examination, and (3) report preparation. A technical memo will serve as the final deliverable.

I. Collecting and Cutting Cores

Approximately 1,000 ft of cored rock samples will be obtained fro the Florida Geological Survey's Core Repository in Tallahassee, FL and transported to the U.S. Geological Survey office in Miami, FL. Hawthorn and Floridan portions of the core samples will be longitudinally slabbed. It appears that three cores of sufficient length and interval in the Lake Okeechobee area may be useful for this task: Well #17000 and 17001 in Highland County and Well #10252 (USGS id: C-851) in Collier County.

Review, examination and evaluation of additional core samples (exceeding the 1,000 ft described above) will be conducted as time and funding permit.

Work will consist of a review of the three cores listed above to determine the well(s) that is(are) best suited for this analysis; the availability of geophysical log and aquifer test data for the selected cored well or in nearby wells will play a role in the decision process. Geophysical logs and aquifer test data for the cored will be obtained and considered in the overall data analysis. If it is determined that none of the above wells are suitable for analysis, work will cease. A description of the integrity and lengths of the intact core will be recorded to expedite subsequent tasks of geotechnical testing, etc.

II. Description of core samples and geologic analysis

Lithologic descriptions of core samples will be prepared taking into account such features as color, bedding thickness, rock types, texture, amount and types of porosity, sedimentary structures, fossils, exposure surfaces, burial features, diagenetic features, fractures, depositional cyclicity, and boundary characteristics of lithologic units. Geophysical log and aquifer test data for the selected sell will be compared t the lithologic descriptions to assess relationships between lithology, geophysical log signatures, hydrogeologic characteristics such as flow zones, etc., and stratigraphic boundaries. Note, it may not be possible to accurately determine the hydrogeologic relationships until additional cores, cuttings, geophysical logs and hydraulic data have been evaluated. This sections of selected samples also will be prepared and analyzed in order to adequately describe details of texture, porosity types, mineralogy, and fossil types. All cores will be photographed to preserve a record of the cores and to enhance subsequent studies of core material.

III. Prepare Log and Report

The core will be lithologically logged with the data assimilated into a descriptive "type log". The "type log" will be presented in a technical memorandum that includes a more detailed description of core samples. Photographs of the core samples considered to be technically significant may be included in the memorandum.

Meetings and Presentations

No presentations or meetings will be required

Schedule