35. Calculating permeability
(i)
(25 marks total)
A cylinder of rock is held vertically. The rock sample has a length of 40 cm and a diameter of 5 cm. Water is pumped through the sample at a rate of 0.06 ml/s upwards. The pressure at the inlet is 130 kPa and the outlet pressure is 101 kPa. Calculate the permeability of the rock. What properties have you had to estimate or look up? (10 marks)
(ii) A rock of the same permeability is used to store carbon dioxide in the subsurface. Under the influence of gravity, in which direction will carbon dioxide move in an aquifer initially saturated with water? Estimate the Darcy velocity for flow under gravity if the viscosity of carbon dioxide is 4x 10-5 Pa.s, its density is 600 kg/m3 and the density of the water (brine) is 1050 kg/m3. (8 marks) (iii) The rock has a porosity of 0.2. The storage aquifer has a height of 100 m. Estimate the time taken for the carbon dioxide to rise 100 m. Comment on your answer – what will prevent escape of the carbon dioxide? (7 marks)