Exploratory Well At Salt Wells Area (Edmiston & Benoit, 1984)
Exploration Activity: Exploratory Well At Salt Wells Area (Edmiston & Benoit, 1984)
|Exploration Activity Details|
|Location||Salt Wells Geothermal Area|
|Exploration Technique||Exploratory Well|
|Activity Date||1980 - 1980|
The blind Salt Wells geothermal system was first identified when Anadarko Petroleum Corporation drilled slim hole and geothermal exploration wells at the site in 1980. Two reports detail the results of this drilling activity. This paper seeks to (1) describe several moderate-temperature (150-200°C) geothermal systems discovered and drilled during the early 1980s that had not been documented previously in the literature, (2) summarize and compare chemical and temperature data from known moderate- to high-temperature (>200°C) in the region, and (3) to comment on the accuracy of the Na-K-Ca and silica geothermometers typically used to estimate reservoir temperatures.
Geothermal surface indications at Salt Wells are described as scant, consisting only of a cold NaCl spring and of sinter deposited from hot springs that were allegedly active during the late 1880s. A 46 km2 thermal anomaly was defined at the Salt Wells geothermal area that extends over 12 km to the south to the Cocoon Mountains. About half of this anomaly is underlain by shallow aquifers that exhibited temperatures of >100°C at less than 100 m depth. In 1980, Anadarko Petroleum Corporation drilled an exploratory confirmation well to a total depth of 2,591 m in Simpson Pass (approximately 30.5 m from the slim hole), in an attempt to intersect a deep fracture system predicted by geological and geophysical studies to occur within a large horst block between two active fault systems. This well was initially drilled to a depth of 213.4 m, and 13-3/8” casing was set to approximately 117 m. The exploratory well penetrated 670 m of volcanic rock before encountering 1921 m of quartz monzonite, both of which were fractured and hydrothermally altered. A temperature gradient reversal was encountered in the well at 106 m depth and 142°C. A temperature gradient of 40 °C/km in quartz monzonite indicates a heat flow of approximately 104 mW/m2. During drilling, the well produced up to about 21 L/s of NaCl water from fractures across a depth interval between 1,859 and 2,057 m, with maximum reservoir temperatures of 160°C. Later, the well was pumped for 100 hours at rates of 110.4 L/s. Flow rates of deeper fractures with fluid entry temperatures up to 177°C were less productive. Maximum temperatures encountered at the bottom of the hole were measured at 181°C. Transmissivity of the reservoir was determined to be 800-900 darcy-feet, as indicated by pressure data from the well. For completion details of the intial slim hole discovery well, see Slim Holes At Salt Wells Area (Combs, Et Al., 1999). For results of geothermometry applied to fluids sampled from the well and local surface discharges, see Geothermometry At Salt Wells Area (Edmiston & Benoit, 1984).
- R.C. Edmiston, W.R. Benoit (1984) Characteristics of Basin and Range Geothermal Systems with Fluid Temperatures of 150°C to 200°C