OPTIMUM WELL-SITE LOCATION FOR THE ROBINSON OIL REFINERY, PALESTINE, ILLINOIS, U.S.A.
William M. Turner, Ph.D.
INTRODUCTION
The Robinson Oil Refinery operated by Marathon Oil Company obtains its cooling water from float-mounted pumps in two large pits that were excavated below the local water table. The client experienced three problems:
1. In the summer, the high temperature of the water decreased efficiency of the refinery's cooling system.
2. Algal growth in the ponds led to fouling of the cooling system.
3. One of the floating platforms sank.
Company officials decided that they needed to change to high capacity water wells to solve their problems.
AGW scientists were contracted to:
1. Determine the ground-water-flow pattern in the area of the refinery.
2. Locate zones of maximum transmissivity and optimum well sites.
3. Identify optimum well-site locations.
4. Locate the coldest ground-water source.
HYDROGEOLOGIC SETTING
The principal aquifer at the refinery is Holocene Wabash River Alluvium, up to 98 feet (30 m) thick, overlying shale of the McLeansboro Formation of Late Pennsylvanian age. Directly west of the refinery, the Wabash River Alluvium pinches out.
Water supplies are developed from the alluvium. Ground water is recharged to the aquifer by direct infiltration of rainfall through the soil horizon.
The alluvium is an accumulation of clastic sediments of varying grain size, sorting and thickness that was deposited by the Wabash River as it meandered over the aggrading valley floor. Consequently, AGW scientists expected that the water transmission characteristics of the aquifer are not uniform.
PROCEDURE
Thermonic data was obtained from specially constructed observation wells 30 feet (10 m) deep and piezometers varying in depth from 72 to 102 feet (22 to 31 m), drilled at strategic locations on property owned by Marathon Oil Company. In addition, Thermonic measurements were taken at existing holes in the Palestine, Illinois area. Marathon provided water levels and collar elevations of the observation wells.
We processed the data to remove effects of varying thermal properties of the soils. We plotted isobathythermonic contours at several different depths using our "valley mapping function."
RESULTS
Our analysis of the data showed that the Neal Pit Pond was the primary ground-water sink and that ground water moved towards it. The Neal Pit behaved as a very large diameter well.
The isobathythermonic contours at 30 feet (10 m) showed three zones of rapid ground-water flow identified as Zones 1, 2, and 3. Zone 1 was clearly the zone of highest ground-water flow.
The isobathythermonic contours at 75 feet (23 m) show that Zone 2 is absent.
Zone 1 at 30 feet (10 m) contains the fastest-moving ground water. At both 30 and 75 feet (10 m and 23 m), Zones 1 and 3 have uniform ground-water-flow rates. Zone 2 exists only between 25 and 50 feet (7.6 and 15.2 m).
Ground-water-level contours of the area around the pits show that ground-water flow is radial but not uniform toward the Neal Pit Pond. The maximum ground-water-flow rate is from southeast to northwest toward the pond. This is consistent with our interpretation of Thermonic data.
CONCLUSION
Thermonic data from both 30 and 75 feet (10 and 23 m) indicate that water transmission characteristics of the aquifer are not uniform and that Zones 1, 2, and 3 are the major zones of ground-water flow towards the Neal Pit Pond. The Thermonic survey indicates that ground water moving through these three zones is colder than ground water elsewhere.
The temperature of water pumped from a fully penetrating well in these zones will remain nearly constant throughout the year at about 56oF (11.7oC). The seasonal variation should be less than two degrees.
RECOMMENDATION
We recommended test production wells be sited within Zone 1. Wells situated in other zones probably would have lower production rates.
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