Oil Material Balance Functions

Calculates effective compressibility for gas reservoir, [1/psi].

Calculates effective compressibility for geopressured reservoir with gas solubility, [1/psi].

Calculates pore volume compressibility term, [1/psi]. cpv = (cw*Swc + cf) / (1 - Swc).

Calculates total system compressibility, [1/psi]. ct = Sg*cg + Sw*cw + cf.

Calculates effective compressibility for undersaturated oil reservoir, [1/psi].

Calculates all drive indices. Returns [DDI, GDI, WDI, CDI, Sum]. Sum should be ~1.

Calculates Compressibility Drive Index (CDI), [fraction 0-1]. CDI = N*Efw / F.

Calculates Depletion Drive Index (DDI), [fraction 0-1]. DDI = N*Eo / F.

Calculates Gas Cap Drive Index (GDI), [fraction 0-1]. GDI = N*m*Eg / F.

Calculates Water Drive Index (WDI), [fraction 0-1]. WDI = We / F.

Calculates two-phase formation volume factor (Bt), [RB/STB]. Bt = Bo + (Rsi-Rs)*Bg.

Calculates formation/water expansion term (Efw), [RB/STB]. Accounts for rock compaction and connate water expansion.

Calculates gas cap expansion term (Eg) for oil reservoirs, [RB/STB]. Eg = Boi*(Bg/Bgi - 1).

Calculates gas expansion for pure gas reservoirs, [RB/scf]. Eg = Bg - Bgi.

Calculates oil and dissolved gas expansion term (Eo), [RB/STB]. Eo = (Bo-Boi) + (Rsi-Rs)*Bg.

Calculates total expansion term (Et), [RB/STB]. Et = Eo + m*Eg + Efw.

Calculates underground withdrawal for gas reservoir, [RB]. F = Gp*Bg + Wp*Bw.

Calculates underground withdrawal for oil reservoir, [RB]. F = Np*(Bo + (Rp-Rs)*Bg) + Wp*Bw.

Estimates N and m from F/Eo vs Eg/Eo regression. Returns [N, m].

Estimates OOIP from F vs Et (no water influx), [STB]. N = F / Et.

Estimates OOIP using regression on F vs Et data, [STB]. Least-squares through origin.

Estimates OOIP with water influx, [STB]. N = (F - We) / Et.

Calculates normalized MBE residual for quality check, [fraction]. Should be close to 0.

Infers water influx from material balance given known OOIP, [RB]. We = F - N*Et.