Light Well Intervention vs. Semisubmersible Rigs

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Questions and Answers

What is one significant advantage of using a Light Well Intervention Vessel (LWIV) over a traditional rig?

Improved safety and efficiency in lifting operations (correct)

Higher day rate costs

Limited mobility to work sites

Longer operational times

Which of the following correctly identifies a phase involved in the Plug and Abandonment (P&A) operations?

Remove the casing string

Set temporary plugs (correct)

Generate well pressure

Install new tubing

What do slickline and braided line systems have in common regarding their use in well interventions?

Both require electric power to function

Both utilize a larger diameter cable

Both are designed for deep water environments

Both are used for measurement and tools (correct)

In the context of decommissioning technologies, which of the following represents a key factor that contributes to cost-effectiveness?

Reduced day rate expenses Signup and view all the answers

Which term correctly defines the operation to kill the well and set plugs in P&A processes?

Phase 0: Preparatory Work Signup and view all the answers

What is one of the primary uses of coiled tubing in decommissioning operations?

To clean out the well prior to plug placement Signup and view all the answers

What disadvantage is associated with section milling during decommissioning?

It can cause easy damage to surface equipment Signup and view all the answers

Which of the following is NOT mentioned as an operational challenge in section milling?

Efficient hole cleaning Signup and view all the answers

Which operation is commonly performed in many plug and abandonment (P&A) operations globally?

Setting primary, secondary, and surface barriers Signup and view all the answers

What factor affects the environmental aims of decommissioning operations?

Equivalent Circulating Densities relative to the formation’s fracture gradient Signup and view all the answers

What financial implication is a noted concern regarding the plug cementing process?

It is time-consuming and hence costly Signup and view all the answers

In the context of coiled tubing, what characteristic distinguishes it from slickline?

It has a larger diameter with an internal fluid passage Signup and view all the answers

Which of the following best describes the procedure involved in milling a window?

Milling through all casing strings and removing cement against the formation Signup and view all the answers

What is the purpose of using suitable fluids and installing plugs in a well during temporary abandonment?

To ensure safety for a defined period. Signup and view all the answers

Which type of well requires temporary plugging for a period of 1-3 years?

Wells currently within production plans but are idle. Signup and view all the answers

What is the significance of the pressure testing of cement plugs?

It indicates the safety and integrity of the formation at the outer casing shoe. Signup and view all the answers

Which method is considered the most expensive for well Plugging and Abandonment (P&A) operations in UK waters?

Utilizing semisubmersible drilling rigs. Signup and view all the answers

What is a disadvantage of using a semisubmersible drilling rig for P&A operations?

It moves more slowly compared to other vessels. Signup and view all the answers

Which of the following underscores the financial implications of decommissioning offshore wells?

The significant daily costs associated with rig operations. Signup and view all the answers

Why is the decision to use a semisubmersible rig for P&A on the Norwegian Continental Shelf limited to specific conditions?

Because it is only viable at water depths beyond the reach of other rigs. Signup and view all the answers

What factor contributes to the rarity of semisubmersible rigs being used for Plugging and Abandonment?

Their high operational costs. Signup and view all the answers

Study Notes

Light Well Intervention Vessel (LWIV)

LWIVs are advantageous compared to rigs due to significant cost and time savings, quicker movement between locations, and improved safety and efficiency in lifting operations.
LWIVs cost approximately 30-40% of the cost of a rig, falling between abandonment using a jackup rig and a semisubmersible rig.
LWIVs are used for preparatory work and complete wellhead and conductor removal in P&A.
LWIVs are used in P&A to kill the well, punch the tubing, set temporary plugs, and remove Christmas trees.

Semisubmersible Drilling Rig

Semisubmersible rigs are the most expensive option for P&A in UK waters, costing around US$5 to 6 million per well.
Semisubmersible rigs are one of the most expensive offshore activities, costing approximately 3 million NOK per day.
Semisubmersible rigs are only viable for P&A beyond the reach of jackup rigs.
Semisubmersible rigs move slower than LWIVs and must be used immediately upon commencement of the contract.

Wireline

Wireline systems are used to run or pull tools and measurement devices into and out of wells for well interventions.
Wireline systems consist of a continuous, small-diameter cable with attached equipment running through an electro-hydraulic or diesel-powered winch.
There are two types of wireline cables: slickline for mechanical operations and braided line (with or without an electric cable) for tractor applications.

Coiled Tubing

Coiled tubing is similar to slickline, but with a larger diameter and an internal passage for pumping fluids.
Coiled tubing is used for cleaning out wells before plug placement and for setting primary, secondary, and surface barriers.

Section Milling

Section milling involves milling a window through all casing strings to allow for cement to be pumped against the formation.
Section milling removes cement, settled mud, and other debris from between the casing and the formation.
Section milling is used in numerous P&A operations globally.

Disadvantages of Section Milling

Section milling can be highly viscous and create swarf.
Swabbing, well control, and hole cleaning can be difficult during section milling.
Section milling can damage surface equipment.

Temporary Abandonment (TA) in Vietnam

Vietnam's legislation defines TA as "bảo quản giếng" - using suitable fluids, installing plugs, and equipment inside the well to ensure safety for a defined period.
TA wells are classified into three types based on their anticipated plugging duration:
- Type 1: Wells plugged for longer than 3 years, including profitable wells without use options.
- Type 2: Wells plugged temporarily for 1-3 years, including wells within production plans but currently idle.
- Type 3: Wells maintained for short durations.
The testing pressure of cement plugs in TA must be greater than the pressure required to test the formation at the outer casing shoe.
High cement plug pressure can result in surface pipe rupture.

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Description

Discover the advantages and disadvantages of Light Well Intervention Vessels (LWIVs) and semisubmersible rigs in offshore operations. This quiz explores cost efficiency, operation speed, and their roles in Plug and Abandon (P&A) processes. Test your understanding of these essential drilling technologies.