Chapter 10 Critical Sour Wells

Question 1

Define a Critical Sour Well?

Answer 1

A designation that reflects the proposed well’s proximity to an urban centre and its maximum potential hydrogen sulphide (H2S) release rate during the drilling stage.

Question 2

At what concentration is H2S gas considered to be immediately dangerous to life and health or IDLH?

Answer 2

100ppm

Question 3

The use of Shear Blind Rams is at the operator’s distraction and/or AER’s request. What are some of the risks of not using Shear Rams?

Answer 3

Shear rams provide an ultimate well barrier to both the drill string and the annulus in the event of a catastrophic surface equipment failure or a drill string failure during the well kill operation.

Question 4

According to IRP #1, What are the minimum BOP equipment requirements for each of the following when drilling critical sour wells?

Answer 4

BOP Stack
-One Annular Preventer
-Two Spools
-Three Rams
One ram is to be located directly below the annular preventer.

Question 5

State the trip tank design for a sour critical well?

Answer 5

A trip tank design in which a change in fluid level of 25mm equals a volume change of no more than 0.08m3 or a maximum surface area of 3m3. The trip tank must be monitored by either a mechanical or automated system and a trip record must be completed for every trip and signed by the rig manager and wellsite supervisor.

Question 6

State the supervisory requirements for drilling personal involved in a critical sour well.

Answer 6

2 operator representatives (12hr shifts)
1 contractor representative
Minimum 5 man crews
2 safety supervisors (12hr shifts)
All personal on site must have a valid H2S certificate
(2-1-5-2)