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Thermochem - High Temperature 2-Phase Downhole Sampler (DHS) / PTS Tool
Geothermal wells are typically sampled for geochemistry at the wellhead, which only provides an average composition of the fluids from depth. Unless the well is pumped, sampling occurs after flashing and scale deposition. Downhole sampling allows vertical profiling of geochemistry with depth, so that each entry can be defined for reservoir model development and simulations. It can also identify specific problematic fluid zones such as high gas, acidic brine or incompatible fluids that cause scaling upon mixing in the wellbore. Pre-flash fluids can be collected before calcium and trace metals have deposited for an accurate reconstruction of the original reservoir fluids.
Traditional downhole sampling tools have several shortcomings:
- The brine flashes as it enters the sample chamber, causing loss of constituents to deposition.
- Sample capacity is severely limited for two-phase fluids and steam zones as sample chamber fills and pressurizes with low-density steam.
- Sample valves are exposed to extreme environments (-250 °C to 350 °C) and often leak and fail.
- Sampler components are not inert and react with the small volumes of sample collected (high reactive surface to sample volume).
- Difficulty in extracting samples and inability to collect representative NCG samples, limited to liquid chemistry only.
Two-Phase Downhole Sampling Solutions
Thermochem has designed an advanced high-temperature two-phase downhole sampling (DHS) tool that is able to withstand temperatures up to 350°C and can recover large sample volumes of 400 ml.
Key design features and benefits of the Thermochem DHS tool include:
- Internal high-tech sample cooler condenses steam and cools brine before the sample chamber and inlet valve, enabling 400 ml of sample to be recovered, even in 100% steam zones.
- The pre-cooling of brine before entering the sample chamber eliminates flashing and loss of trace species to deposition.
- Pre-cooled fluids allow the use of highly reliable, leak-tight sample valves.
- The sample cooler is filled with a eutectic material that has a higher heat capacity per volume than ice.
- The pre-cooler also functions as a total heat calorimeter, enabling measurement of the steam to brine ratio, so that samples collected in the two-phase zone can be reconstructed to wellbore conditions.