06.08.2013 Views

Sequential Methods for Coupled Geomechanics and Multiphase Flow

Sequential Methods for Coupled Geomechanics and Multiphase Flow

Sequential Methods for Coupled Geomechanics and Multiphase Flow

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

230 APPENDIX B. MISCELLANEOUS DERIVATIONS<br />

Remark D.2. Assume 1D oil-water flow with capillarity with σv ˙ = 0 in order to study<br />

the properties of Equations B.12 – B.14 in a numerical sense. Using Equations B.12 – B.14,<br />

the governing equations become<br />

where N is<br />

⎡<br />

⎣ Noo Now<br />

Nwo Nww<br />

⎡<br />

⎣ Noo<br />

⎤⎡<br />

Now<br />

⎦⎣<br />

<br />

Nwo Nww<br />

<br />

N<br />

<br />

˙ po<br />

pw ˙<br />

σv ˙ = Kdr ˙<br />

⎤<br />

⎦ =<br />

⎡<br />

εv − b (So ˙<br />

⎤<br />

⎦ + b<br />

po + Sw ˙<br />

⎡<br />

pw)<br />

<br />

bJ ˙<br />

pJ<br />

⎣ φSoco − φ dSw<br />

dpco<br />

⎣ So<br />

Sw<br />

<br />

−<br />

+ So b−φ<br />

Ks So<br />

φ dSw b−φ<br />

+ Sw dpco Ks So<br />

⎤<br />

⎦εv ˙ =<br />

⎡<br />

⎣ − Div vo + fo<br />

− Div vw + fw<br />

⎤<br />

⎦, (B.16)<br />

<br />

dSw<br />

−bpco ( po ˙ − pw) ˙ , (B.17)<br />

dpco<br />

<br />

˜<br />

bJ ˙<br />

SJ<br />

φ dSw b−φ<br />

+ So dpco Ks Sw<br />

φSwcw − φ dSw b−φ<br />

+ Sw dpco Ks Sw<br />

Then, substituting Equation B.17 into Equation B.16 <strong>and</strong> using σv ˙ = 0, we obtain<br />

⎛<br />

⎜⎡<br />

⎜<br />

⎜⎣<br />

⎜<br />

⎝<br />

Noo<br />

⎤<br />

Now<br />

⎦<br />

Nwo Nww<br />

<br />

N<br />

+ b2<br />

Kdr<br />

⎡<br />

⎣ S2 o SoSw<br />

SwSo S 2 w<br />

⎤<br />

⎦<br />

<br />

˜S<br />

− b2 dSw<br />

pco<br />

Kdr dpco<br />

<br />

=<br />

⎡<br />

⎣ − Div vo + fo<br />

− Div vw + fw<br />

⎤<br />

W<br />

¯S<br />

⎞<br />

⎤<br />

⎦.<br />

⎡<br />

⎣ So<br />

⎤⎟⎡<br />

−So<br />

⎟<br />

⎦ ⎟<br />

⎟⎣<br />

⎟<br />

Sw −Sw ⎠<br />

<br />

˙ po<br />

pw ˙<br />

⎦. (B.18)<br />

For the left terms of Equation B.18, the positive-definiteness of W is not guaranteed<br />

because ¯ S is indefinite. This is the case even though N <strong>and</strong> ˜ S are positive-definite <strong>and</strong><br />

positive-semidefinite, respectively. The eigenvalues of ¯ S are 0, So − Sw. When |pco| <strong>and</strong><br />

|dSw/dpco| are large enough such N <strong>and</strong> ˜ S are ignored, we may face an ill-posed problem.<br />

⎤<br />

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!