Norway remains fiercely dedicated to protecting its offshore waters. As a result, it is one of the most challenging regions in which to carry out well service operations involving chemicals and fluids.

To protect the environment, the OSPAR Commission for the Protection of the Marine Environment of the Northeast Atlantic established guidelines for the screening of chemicals

To develop its PLONOR-only cementing chemicals package, BJ tested numerous chemicals and additives at its base in Tananger, Norway. (Photo courtesy of BJ Services)

and additives for use by the offshore industry. Norwegian authorities use these guidelines as one of their tools to regulate offshore activity. The guidelines grade all chemicals based on the risk each poses to the marine environment. In Norway, the chemicals are then placed in one of four color-coded categories. Green category chemicals are those included on an OSPAR list of substances which Pose Little Or NO Risk to the environment (PLONOR). They need no testing and may be used without limitation. All other chemicals must be tested and assessed under OSPAR pre-screening protocols. Yellow category chemicals have been tested and pass the pre-screening and are considered environmentally acceptable but require a permit for use. Red category chemicals should be avoided where possible because they have failed the pre-screening due to low biodegradation, high bioaccumulation potential or high toxicity, and the components involved must be prioritized for replacement. Black category chemicals have very poor pre-screening results or are on an exclusion list and may not be discharged to the environment.

For many years BJ Services has worked to comply with Norway’s increasingly rigorous and complex environmental standards. Its people invest a great deal of time researching and carefully analyzing components for the additives in its cementing product line. In keeping with Norway’s stringent environmental legislation, the company has been developing new additives using components from the PLONOR list. The greatest challenge is achieving these goals without compromising the performance of the cement slurry. Overall, the company’s aim is to develop a cementing additives package consisting of a defoamer, dispersant, retarder, gas migration control and fluid loss additive made up of solely of PLONOR substances.

Defoamer

The service company achieved an important milestone by developing and field-testing a new PLONOR defoamer (patent pending). Although it is typically the additive with the lowest concentration in the cement slurry, the new product is projected to have a significant impact because a defoamer is necessary in all cement slurries.

In field and laboratory tests, the new PLONOR defoamer showed good performance compared with traditional defoamers. Using this new defoamer on future surface casing jobs with API Class “G” cement will make it possible to perform these operations with discharge of PLONOR-only substances to the seabed.

First cementing operation

The company currently provides Hydro with cementing and pumping services for a number of its assets located on the Norwegian Continental Shelf in accordance with a 3-year contract that was awarded in 2005.

The PLONOR defoamer field test was carried out earlier this year in a 13 3/8-in. cementing operation for Hydro in the Troll field, Block 31/2, well 013A. Work was carried out from the semisubmersible drilling rig Songa Dee. The successful cementing operation demonstrated that this Green-category defoamer could fully replace the Yellow-category alternatives. As a result of the field test, Hydro has registered the defoamer for use in cementing operations carried out on its assets.

Persistence produces results

The successful performance of the PLONOR cementing package provides a launching pad for plans to pump the first fully PLONOR, gas-tight cement slurry in the near future, an industry first.

The R&D road

The quest for a PLONOR-only cementing chemicals package began in 2000. Efforts to create an alternative defoamer involved company scientists in Germany developing and producing

	Transocean’s Polar Pioneer will pump a new environmentally friendly, gas-tight cement slurry this winter in the Barents Sea. (Photo courtesy of Transocean)

the new formulations and service company-Norway personnel conducting qualification tests of the products. In addition to samples produced by the service company’s blending plant in Germany, several samples from external vendors were tested. The only two products that satisfied all testing criteria were FP-16LG, the company’s current defoamer, which was classified Yellow at the time, and the new PLONOR defoamer FP-23L. Today, the new defoamer is the first and only product made solely from substances on the PLONOR list.

Dispersant

To offer a full gas-tight PLONOR cement system, the service company faced the challenge of finding a replacement for its dispersant and fluid loss additives. It found a new PLONOR dispersant that works effectively over a wide temperature range with minimal impact on slurry thickening time, an additive it calls CD-35L, that is manufactured in Norway.
At the company’s laboratory in Tananger, Norway, technicians re-tested a cement slurry containing SL-1 liquid silica suspension, using the new CD-35L as the dispersant. With half as much dispersant loading as previously required, the rheology dropped from 86 cp to 31 cp at 300 rpm, enabling turbulent flow from the slurry. The CD-35L dispersant was successfully introduced in the field for the first time in December 2005 during a cementing operation for another operator in the Barents Sea, offshore Norway, in a 9 5/8-in. casing cementing operation consisting of a gas-tight lead slurry and a standard tail slurry.

The final piece

Beyond developing a PLONOR defoamer and dispersant, the final piece of the puzzle was to create a PLONOR fluid-loss additive. Working with the service company’s research and development personnel in Tomball, Texas, the European team decided to work with the fluid loss additive FL-52. An aqueous version known as FL-52L was developed along with the dry version. Both are key elements of the new PLONOR well cementing package.

Field trials

Cement laboratory testing using these new products along with some existing PLONOR additives has demonstrated that a gas-tight slurry is achieved, meaning that the slurry is appropriate for zonal isolation of gas-bearing formations. Looking ahead, plans are under way to field-test the first PLONOR gas-tight cement slurry this winter for Hydro. The new slurry will be pumped from a semisubmersible drilling rig in the Barents Sea offshore Norway.
 
Beyond the North Sea

An increasing number of operators are beginning to apply North Sea environmental standards to their operations in other regions of the world such as Africa. Following the new European directive for reduced chromium-VI levels in cement, the company will try to ensure that any European-sourced cement ordered by its African operations will meet the same standards.