Reverse cementing float equipment

1. A regulating valve assembly for regulating fluid flow through a passage, the assembly comprising:

a back-flow valve comprising a seat and a closure element, wherein the closure element engages with the seat in a closed configuration and disengages from the seat in an open configuration;

a lock in mechanical communication with the back-flow valve to lock the back-flow valve in the open configuration;

a forward-flow valve in mechanical communication with the lock and comprising a seat and a closure element, wherein the closure element engages with the seat in a closed configuration and disengages from the seat in an open configuration;

wherein the back-flow valve and the forward-flow valve operate independently; and

wherein the lock disengages in response to forward fluid flow.

2. A regulating valve assembly as claimed in claim 1 , wherein the closure element of the back-flow valve is a flapper biased to the closed configuration.

3. A regulating valve assembly as claimed in claim 1 , wherein the lock comprises a sleeve.

4. A regulating valve assembly as claimed in claim 1 , wherein the lock comprises a sleeve, wherein the sleeve locks the back-flow valve in the open configuration when the sleeve is stung in the seat of the back-flow valve and unlocks the back-flow valve when the sleeve is unstung from the seat of the back-flow valve.

5. A regulating valve assembly as claimed in claim 1 , wherein the closure element of the forward-flow valve is a flapper biased to the closed configuration.

6. A regulating valve assembly for regulating fluid flow through a passage, the assembly comprising:

a back-flow valve comprising a seat and a closure element, wherein the closure element engages with the seat in a closed configuration and disengages from the seat in an open configuration;

a sleeve, wherein the sleeve stings into the seat of the back-flow valve when the back-flow valve is in the open configuration and unstings from the seat of the back-flow valve when the back-flow valve is in the closed configuration;

a forward-flow valve positioned with the sleeve and comprising a seat and a closure element, wherein the closure element engages with the seat in a closed configuration and disengages from the seat in an open configuration;

wherein the back-flow valve and the forward-flow valve operate independently; and

wherein the sleeve unstings in response to forward fluid flow.

7. A regulating valve assembly as claimed in claim 6 , wherein the closure element of the back-flow valve is a flapper biased to the closed configuration.

8. A regulating valve assembly as claimed in claim 6 , wherein the closure element of the forward-flow valve is a flapper biased to the closed configuration.

9. A method for reverse-cementing casing in a wellbore, the method comprising:

locking a back-flow valve in an open configuration and making the back-flow valve up to the casing;

making a forward-flow valve up to the casing, wherein the forward-flow valve allows fluid to flow into the casing inner diameter and restricts fluid flow out of the casing inner diameter.

running the casing equipped with the back-flow valve and the forward-flow valve into the wellbore to a target depth;

reverse-circulating a cement composition into an annulus defined in the wellbore by the casing;

taking fluid returns through the back-flow valve as the cement composition is reverse-circulated into the annulus;

unlocking the back-flow valve; and

closing the back-flow valve, whereby the cement composition is retained in the annulus by the back-flow valve.

10. A method for reverse-cementing casing in a wellbore as claimed in claim 9 , wherein the locking a valve in an open position comprises stinging a sleeve into a flapper seat of the back-flow valve, and wherein the closing the back-flow valve comprises unstinging a sleeve from the flapper seat of the back-flow valve.

11. A method for reverse-cementing casing in a wellbore as claimed in claim 9 , wherein the taking fluid returns through the back-flow valve as the cement composition is reverse-circulated into the annulus comprises flowing the returns through the forward-flow valve.

12. A method for reverse-cementing casing in a wellbore as claimed in claim 9 , wherein the unlocking the back-flow valve comprises closing the forward-flow valve to restrict fluid flow from the inner diameter of the casing to the annulus and increasing the fluid pressure in the inner diameter of the casing.

13. A method for reverse-cementing casing in a wellbore as claimed in claim 9 , further comprising restricting fluid flow from the annulus into the inner diameter of the casing so as to float the casing as the casing is run into the wellbore.

14. A method for reverse-cementing casing in a wellbore as claimed in claim 9 , further comprising choking fluid flow from the wellbore into the inner diameter of the casing, wherein fluid flow in the reverse-circulation direction is slowed.