A massive gas sand at 10,000 ft having a porosity of 0.30 and a water saturation...

 

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A massive gas sand at 10,000 ft having a porosity of 0.30 and a water saturation of 0.35 is being drilled at a rate of 80 ft/hr using a 9.875-in. bit. The drilling mud has a density of 12 lbm/gal and is being circulated at a rate of 400 gal/min. The an- nular capacity is 2.8 gal/ft. The mean temperature of the well is 600°R. Ignore the slip velocity of the gas bubbles and rock cuttings. a. After steady-state conditions are reached, what is the effective bottomhole pressure? Assume that the gas is pure methane and behaves as an ideal gas. Answer: 6,205 psia. b. What is the equivalent mud weight in the an- nulus? Answer: 11.9 lbm/gal. c. What is the mud density of the mud leaving the annulus at the surface at atmospheric pressure? Answer: 5.8 lbm/gal. d. Make a plot of the density of the drilling fluid in the annulus vs. depth. e. Can the gas-cut mud at the surface be eliminated completely by increasing the mud densi- tv? Answer: no. A massive gas sand at 10,000 ft having a porosity of 0.30 and a water saturation of 0.35 is being drilled at a rate of 80 ft/hr using a 9.875-in. bit. The drilling mud has a density of 12 lbm/gal and is being circulated at a rate of 400 gal/min. The an- nular capacity is 2.8 gal/ft. The mean temperature of the well is 600°R. Ignore the slip velocity of the gas bubbles and rock cuttings. a. After steady-state conditions are reached, what is the effective bottomhole pressure? Assume that the gas is pure methane and behaves as an ideal gas. Answer: 6,205 psia. b. What is the equivalent mud weight in the an- nulus? Answer: 11.9 lbm/gal. c. What is the mud density of the mud leaving the annulus at the surface at atmospheric pressure? Answer: 5.8 lbm/gal. d. Make a plot of the density of the drilling fluid in the annulus vs. depth. e. Can the gas-cut mud at the surface be eliminated completely by increasing the mud densi- tv? Answer: no.