Lateral Flow - Transient Activity
Transient lateral flow is very common in geothermal systems. Areas where there have been recent faulting are the most likely to find the transient flow. The term transient is used here on a geologic time-table. The length of time the flow will occur is dependent on the source of fluids and their chemistry. Faults will seal over time from crystallization of the minerals in the water precipitating out. The unusually hot water flows convectively up the fault until it reaches an aquifer or the water table. Where the fault and aquifer intercept is where the flow will become lateral. The heated fluid flowing laterally can be very deceiving when determining the size of a geothermal area. Many a driller has thought that they hit the geothermal jackpot only to keep drilling and watch the temperatures decrease with depth once through the lateral flow. These temperature-depth curves do contain information on the duration of flow, velocity, distance to recharge point and temperature of recharge.