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No error but I am getting Complex double!

12 次查看（过去 30 天）
Sarah A Alruwayi
Sarah A Alruwayi 2019-3-1
回答： Walter Roberson 2019-3-1
clear ALL
close ALL
clc
Area=0.1963;
L=4;
porosity=0.18;
K=61.5;
injrate=0.01;
oilvisc=4.2;
watervisc=0.85;
Boi=1.21;
Swr=0.28;
Sorw=0.35;
KrwMax=0.31;
KroMax=0.65;
Nw=2.25;
No=2.45;
CO=0.000001;
CW=0.000004;
CR=0.000003;
POi=1500;
PWF=1460;
dt=0.2;
Vr=Area*0.4;
for i=1:10
Swi(1,i)=Swr;
PO(1,i)=POi;
PCOW(1,i)=5;
Krw(1,i)=KrwMax*((Swi(1,i)-Swr)/(1-Sorw-Swr))^Nw;
Kro(1,i)=KroMax*((1-Swi(1,i)-Sorw)/(1-Sorw-Swr))^No;
Omob(1,i)= Kro(1,i)/oilvisc;
Wmob(1,i)=Krw(1,i)/watervisc;
end
for n=1:15
for i=1:10
Ctot(n,:)=CR+Swi(n,:)*CW+(1-Swi(n,:))*CO;
if i==1
Ttot=(2.6366e-4)*K*(Wmob(n,i)+Omob(n,i))*(Area/0.4);
Tw=(2.6366e-4)*K*(Wmob(n,i))*(Area/0.4);
A(i,i)=-(Ttot+(Vr*porosity*Ctot(n,i))/(dt)); %E
A(i,i+1)=Ttot; %F
R(i,1)= (-(Vr*porosity*Ctot(n,i)*PO(n,i))/(dt))+Tw*(PCOW(n,i+1)-PCOW(n,i))-injrate; %R
elseif i==10
WI(n,i)=(2.6366e-4)*K*(Wmob(n,i)+Omob(n,i))*(Area/(0.4/2));
TtotL=Ttot;
TwL=Tw;
Ttot=0;
Tw=0;
%Ttot=2.6366*10^-4*K*(Wmob(n,i)+Omob(n,i))*(A/0.4);
%Tw=2.6366*10^-4*K*(Wmob(n,i))*(A/0.4);
A(i,i-1)=TtotL; %D
A(i,i)=-(TtotL+((Vr*porosity*Ctot(n,i))/(dt))+WI(n,i)); %E
R(i,1)=(-(Vr*porosity*Ctot(n,i)*PO(n,i))/(dt))-TwL*(PCOW(n,i)-PCOW(n,i-1))-WI(n,i)*PWF; %R
else
TtotL=Ttot;
TwL=Tw;
Ttot=(2.6366e-4)*K*(Wmob(n,i)+Omob(n,i))*(Area/0.4);
Tw=(2.6366e-4)*K*(Wmob(n,i))*(Area/0.4);
A(i,i)=-(TtotL+Ttot+(Vr*porosity*Ctot(n,i))/dt); %E
A(i,i+1)=Ttot; %F
A(i,i-1)=TtotL; %D
R(i,1)= (-(Vr*porosity*Ctot(n,i)*PO(n,i))/(dt))+Tw*(PCOW(n,i+1)-PCOW(n,i))-TwL*(PCOW(n,i)-PCOW(n,i-1)); %R
end
end
PO(n+1,:)=A\R;
for i=1:10
if i==1
q_t(n,i)=injrate;
Tw=(2.6366e-4)*K*(Wmob(n,i))*(Area/0.4);
Swi(n+1,i)= (1+(CR+CW)*(PO(n+1,i)-PO(n,i)))*Swi(n,i)+...
(dt/(Vr*porosity))*(Tw*(PO(n+1,i+1)-PO(n+1,i))-...
Tw*(PCOW(n,i+1)-PCOW(n,i))+q_t(n,i));
elseif i==10
TwL=Tw;
Tw=0;
WI(n,i)=(2.6366e-4)*K*(Wmob(n,i)+Omob(n,i))*(Area/(0.4/2));
qt(n,i)= -WI(n,i)*(PO(n+1,i)-PWF);
Swi(n+1,i)=(1+(CR+CW)*(PO(n+1,i)-PO(n,i)))*Swi(n,i)+dt/(Vr*porosity)*...
(-TwL*(PO(n+1,i)-PO(n+1,i-1))+TwL*(PCOW(n,i)-PCOW(n,i-1))+qt(n,i));
else
TwL=Tw;
Tw=2.6366e-4*K*(Wmob(n,i))*(Area/0.4);
Swi(n+1,i)=(1+(CR+CW)*(PO(n+1,i)-PO(n,i)))*Swi(n,i)+ ...
(0.2/(Vr*porosity))*Tw*(PO(n+1,i+1)-PO(n+1,i))-...
TwL*(PO(n+1,i)-PO(n+1,i-1))-Tw*(PCOW(n,i+1)-PCOW(n,i))+TwL*(PCOW(n,i)-PCOW(n,i-1));
end
if Swi(n+1,i)<Swr
Swi(n+1,i)=Swr;
end
end
for i=1:10
if Swi(n+1,i)<=Swr
PCOW(n+1,i)=5;
elseif Swi(n+1,i)>=(1-Sorw)
PCOW(n+1,i)=-5;
elseif Swi(n+1,i)>Swr && Swi(n+1,i)<0.5
PCOW(n+1,i)= min(-0.8*log((Swi(n+1,i)-Swr)/(0.5-Swr)),5);
elseif Swi(n+1,i)>0.5 && Swi(n+1)<(1-Sorw)
PCOW(n+1,i)=max(0.8*log((1-Swi(n+1,i)-Sorw)/(1-0.5-Sorw)),-5);
end
end
for i=1:10
Krw(n+1,i)=KrwMax*((Swi(n+1,i)-Swr)/(1-Sorw-Swr))^Nw;
Kro(n+1,i)=KroMax*((1-Swi(n+1,i)-Sorw)/(1-Sorw-Swr))^No;
Omob(n+1,i)= Krw(n+1,i)/watervisc;
Wmob(n+1,i)=Kro(n+1,i)/oilvisc;
end
end

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回答（2 个）

Mark Sherstan
Mark Sherstan 2019-3-1
You should not use i or j as the names of loop variables as these are both names for the inbuilt imaginary unit. Try changing that and see if the problem persisits.
  1 个评论
Sarah A Alruwayi
Sarah A Alruwayi 2019-3-1
My friend has exactly the same code and got it right and she named the loops i as well.So, I do not think this is the problem

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Walter Roberson
Walter Roberson 2019-3-1
When n = 4, i = 1, then 1-Swi(n+1),i)-Sorw becomes negative, so (1-Swi(n+1,i)-Sorw)/(1-Sorw-Swr) becomes negative. You are raising a negative value to a non-integer. A^B with scalar A, B is defined as exp(B*LOG(A)) so when A<0 the log is complex and unless B is an integer you get a complex result from the ^ operation. Everything else gets tainted from there.

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