Final4Practice - NAME _ UT EID _ Signature _ PGE 421K...

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NAME _____________________ Signature _________________ UT EID ____________________ PGE 421K SPRING 2007 FINAL EXAM Open Notes, Open Book. No computers. Work all 8 problems on the exam paper; blank pages are included. No credit for answers without units or with incorrect dimensions. All problems are self- explanatory. If you think you need more information, make a reasonable assumption, write it down, explain it and carry on. 1) 50 million metric tons of CO 2 have been injected into a depleted gas field as sketched below. The formation dips at an angle of 10 degrees. It is sealed at the updip end by a fault. Over the aquifer is a brittle shale layer (not shown). Natural fractures are forming in the shale because of movement associated with the fault. The natural fractures can be modeled as vertical slits of aperture b (see sketch). The curvature of a meniscus in a fracture is given by C = 2cos / b where is the contact angle. Data Density of CO 2 700 kg/m 3 Interfacial energies: CO2-brine 0.10 J/m 2 CO2-shale 0.20 J/m 2 brine-shale 0.12 J/m 2 Formation width 2000 m Formation thickness 100 m Formation porosity 0.15 a. What is the nonwetting phase for the shale? i. CO 2 ii. Brine iii. Oil b. How large must the aperture become before the CO 2 begins to leak through the natural fractures at the updip end of the formation? 10 points
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(workspace for Problem 1)
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2) The diagram above illustrates a system operating at steady state. For the control volume shown, the following relationships are known: ;0 ; ; 2 ab b a a mm Q zzuu b   .
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Final4Practice - NAME _ UT EID _ Signature _ PGE 421K...

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