Zonal isolation - what are effective alternatives to cement?

By Jonny Haugen - October 20, 2017

Zonal isolation - what are effective alternatives to cement?

Cement has been central to well integrity since 1906. Now, the oil companies are searching for new and better ways for zonal isolations in oil and gas wells. What are the trends and alternatives to cement? 

Image: Crescent Petroleum/Icethorn (Wikimedia commons)

You really don't want change in pressure or visual gas leaks on the seafloor or surface. Sustained casing pressure or annulus pressure build up will force you to shut down the drilling.

The consequence? Lost production or delays in the drilling operation. If you are a drilling operation manager, you know the extra costs of delays and shutdowns. We don´t want that to happen! 

A long history of cement

During the drilling process, you will have to do several tests to make sure that you have correct pressure and a nonleaking well.

Cementing is central to the discussion of zonal isolation and well integrity because cement typically provides at least one barrier in a well and is a component of the barrier envelope or barrier system during well construction and the operational phases of the well.

Reading tip: Lab tests to review when designing a "gas tight" cement slurry

Gunnar DeBruijn at Schlumberger is a member of the JPT Editorial Committee. He has been working with cement in North America and in deep water around the world, supporting cementing and well integrity initiatives.

“There is a long history of industry standards for cementing, with the American Petroleum Institute establishing the first cementing standard in 1948. In the last several years, regulations have been updated and rewritten worldwide.

In every jurisdiction, we can point to a regulation or industry standard that affects drilling and cementing operations. This regulatory attention compels us to double-check our practices, continue effective techniques, and develop technology where improvements are needed.

Technology is also focused on improving verification of cement placement and barrier achievement. Cement evaluation, including wellsite observations during cement placement, pressure tests, and logging techniques, are part of the well-integrity equation. These enhanced evaluation methods provide confidence that zonal isolation and well integrity are achieved.”

Why is this important?

Because working as an operation manager in an oil company and being in charge of purchasing, you must be aware of:

  • Your company's requirements for sealing and barriers. These will typically be linked to regulatory requirements
  • The established processes that your company currently have regarding zone insulation, and typically know the specific challenges they have
  • Alternative solutions and suppliers that can contribute when the issue arises
  • The cost the company has with such problems, and be interested in understanding, or be working with partners for improved or new solutions 

When a major North Sea operator had challenges with loose conductors due to cement fracturing the soft formation from the seabed and downwards, alternatives was required.

Specifically, the solution had to be both thin and penetrable through a mix of cement pieces and formation. In addition, it had to be heavy enough to displace existing mud and sea water without fracturing the formation.

To combine these requirements, it became evident that an alternative to cement was required. A better sealant solution would be a material with low viscosity and high density, but still flexible and strong when set.

Read also our case on whater shut off in horizontal wells

In search of alternatives

Cement in different qualities has been the answer to well integrity for more than a century. Now there are a lot of activities around the world looking for other ways to deal with the same problems. It is challenging today's technologies.

There are several collaborative projects between companies in several countries that is looking for better solutions where long-term sealing is central.

For instance, major oilfield service companies, providing cementing solutions, also works to find better solutions to their own cement. In particular, they are looking at resins in (or in combination with) their cement.

Reccomended reading: Resin curing process

Wellcem has provided information to several Joint Industry Projects about alternatives to cement, which are:

  • More flexible, plastic, so they do not crack or break up so easily
  • More lasting and better sealed, also when pressure and temperature change in the wells
  • Can be delivered and placed faster - to a lower total cost
  • Demonstrates a higher success rate

This is because it takes a lot of efforts and additional costs when a well has to be shut down due to leakage. Cement is still the dominant product used to seal oil and gas wells. It is challenged in a number of areas, and many players in the oil industry are looking for more flexible and environmentally friendly alternatives.

Resins are more often included in the assessment of new projects. You will need to learn more about these products and what trends are now entering the market.

Questions or comments? Please add to the discussion in the comments field below.

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