# Pump fluid down HPHT gas well - fluid remains at top

Working offshore on a High Pressure / High Temperature gas well. We pumped 120 barrels of organic solvent into the well. The gas density was 0.3kg/m3. The fluid was 0.8kg/m3 & a boiling point of 85 degrees C (at 1 atm). The well is 5km long / deep. The initial surface pressure is 5,000 psi. The bottom hole temperature is +/- 180 degrees C. We pumped in fluid & saw surface pressure reduce to +/- 3,500 psi. We only pumped 2km worth of fluid. We pumped the fluid slowly & hoped it would fall to the bottom of the hole. However, it didn't. It remained suspended at surface. Can anyone explain why? Not sure if liquid is boiling & condensing at top of well. However, the closed in pressure is confusing the issue.

• Help me understand. The well is full with gas at 0.3kg/m3? And the organic solvent is also a gas at 0.8kg/m3? Just checking since you call the solvent a fluid. (Would you mind sharing a phase diagram of that?)
– rfl
Jan 12, 2022 at 19:40
• @Strevz : Your figures do not make sense. I am not sure natural gas can have density of 0.3 kg/m3 even at 1 atm and 180 deg C, let alone at 5000+ psi. You should probably replace kg/m3 with kg/L everywhere. Jan 13, 2022 at 8:21

This answer is wrong, will remove when we have figured this out...

Could your well be filled with water, and the solvent floats on top? Water is liquid at these and pressures and temperatures. Liquids are nearly incompressible, so the density is just ~1kg/liter. Now you pour a liquid on top of that with a much lower density (do you really mean 0.8kg/m3 or rather 0.8kg/liter? ...anyway.) - so that will simply float on top of the water.

• Thanks for answer, but no, the well is full of gas with a average density of 0.3kg/m3. I think the liquid is staying on top because the bottom of the hole is so hot. The pressure is relatively equal accept for the hydrostatic difference of the gas (more pressure at bottom - equal to reservoir pressure). Jan 12, 2022 at 19:01
• I'll remove the answer later but leave it for now so folks know that that's not it. Hmmmm... curious! :)
– rfl
Jan 12, 2022 at 19:37