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Sequential Methods for Coupled Geomechanics and Multiphase Flow

Sequential Methods for Coupled Geomechanics and Multiphase Flow

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226 APPENDIX B. MISCELLANEOUS DERIVATIONS<br />

P co<br />

Schematic capillary pressure P co<br />

0 1<br />

S w<br />

P cg<br />

Schematic capillary pressure P cg<br />

0 1<br />

S g<br />

Figure B.1: Typical shapes of capillary pressure regarding wetting <strong>and</strong> non-wetting phases<br />

(e.g., Sw <strong>and</strong> Sg, respectively). pco = po − pw, <strong>and</strong> pcg = pg − po. The capillary pressure<br />

curves are drawn based on the work of Lenhard <strong>and</strong> Parker (1987)<br />

Note from Chapter 2 that N −1 = M <strong>and</strong> both N <strong>and</strong> M are symmetric. Then we obtain<br />

p t Np = p 2 oNoo + p 2 wNww + p 2 gNgg + 2Nowpopw + 2Nogpopg + 2Nwgpwpg<br />

= φSocop 2 o + φSwcwp 2 w + φSgcgp 2 g − φ dSw<br />

dpco<br />

2<br />

po − 2popw + p 2 <br />

w<br />

+φ dSg 2<br />

po − 2popg + p<br />

dpcg<br />

2 b − φ 2<br />

g + Sop Ks<br />

2 o + S 2 wp 2 w + S 2 gp 2 g<br />

+2SoSwpopw + 2SoSgpopg + 2SwSgpwpg)<br />

= φ Socop 2 o + Swcwp 2 w + Sgcgp 2 dSw<br />

g − φ (po − pw)<br />

dpco<br />

2 + φ dSg<br />

(po − pg)<br />

dpcg<br />

2<br />

+ b − φ<br />

(Sopo + Swpw + Sgpg)<br />

Ks<br />

2<br />

≥ 0, (B.3)<br />

where the equality is only satisfied with p = 0. Hence, N is positive-definite, from which<br />

M is also positive-definite.

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