Question

c.Sometimes, the pipes are over the surface and sometimes below the surface, what are challenges for both ways

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d. ‘Perforating gun punches a hole through the casing and cement walls, and production formation’. Is this practice always possible? If not, how it can be made better?

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e.Why do you think, the maximum value for the range of diameter of casing is to be fixed? Give two reasons.

Answer 1

1) When pipes are over the surface, they have to be made of such a material that will be resistant to the ever-changing environmental conditions. It should satisfy its functions over its design period. The surface has many undulations because it is not always plain and therefore, many turns in the path of the laying of pipes come. These turns require additional requirements like a drop manhole, side fencing, and protective cover, etc. This adds to the cost of laying. If it is a steel pipe then corrosion is another big problem.

When pipes are laid underground, then also there is restriction on their paths as they may interfere with the existing pipes or electric or telephonic lines. The excavation costs of such pipes is huge. They should be made tough enough to resist the overburden pressure. Their maintenance is costlier than surface pipes.    

2) The function of perforating gun involves piercing holes through walls and casing but this is not always possible particularly when the thickness of the elements is more and perforating gun is not designed for it. In that case for concreting, we have to go for conventional methods of pouring concrete.

3) The maximum diameter of the casing should be fixed because i) Larger diameter may lead to separation of workable concrete inside it and this will worsen the pipe performance and moreover this will degrade the concreting pipe walls from inner because of the less presuure created in the area where seperation has occured.

ii) Pipes can supply concret continuasly only upto a partcular pipe diameter and that too depends on pump characteriswtics and power.