Field Trial of Alternative Weight Material with Improved Occupational Hygiene and Environmental Performance

Abstract

Barite has to date been the most common weighting material for drillingfluids. Several heavy metal components are associated with the barite. During discharge of drilled cuttings from the use of water based drilling fluid some parts of these heavy metals can be dissolved into the sea. If oil based drilling fluid is used no discharge of drilled cuttings is allowed into the seaon the Norwegian Continental shelf. This cuttings can be re-injected into the formation or can be brought onshore for treatment. If barite is heated to more than 850°C during this treatment, the toxic component barium oxide may be released. The negative impacts from the use of barite in drilling fluids can be avoided if an alternative weight material is used. On the Norne field in Norway a field trial was performed using ilmenite as the weighting material. The paper describes the improved heavy metal content of the ilmenite compared to the barite. Furthermore, it is shown that the heavymetals present are not as biologically available in ilmenite as in barite. The paper describe how the ilmenite improved the ability for the fluid to be recycled and reused. Ilmenite is more resistant to grinding during the drillingprocess, resulting in more stable particle size distribution. This implies a reduced need for dilution of the drilling fluid. This leads to reduced discharges to the sea if water based drilling fluid is used, and less volume tohandle and treat in the case of oil based drilling. The dark color of the ilmenite made it easier to detect and repair any leaks in the transport and bulk handling systems offshore. This will lead to reduced dust problems and an improved occupational hygiene. No significant dust problems were observed during the test at Norne. Introduction Current drilling practice is to use water based drilling fluids whenever feasible, since permanent depositions on the sea bed of cuttings produced when drilled with these water based drilling fluids are allowed. Still, there is a major emphasis onto minimizing the negative impacts from drilling operations on the environment. This emphasis covers the change to less and less harmful chemicals in the drilling operations. Even some of the minerals added to the drilling fluid may contribute to the environmental impact. The leaching of heavy metals from weighting agents to the sea may give a negative impact. The heavy metal content of ilmenite is lower on most components than that of barite. In addition is the bio-availability of the heavy metals lower. Therefore, it is believed to be more desirable to use materials like ilmenitethan barite as weighting agents in drilling fluids. History Ilmenite has been applied earlier in drilling operations in the North Sea. Two tests have been conducted. In the first test two wells were drilled in 1979and 1980 with ilmenite weighted drilling fluids. The ilmenite was a fairly coarse ground material compared to the presently used ilmenite. According to Blomberg et al (1), the drilling fluid properties were easier to control compared to drilling with barite. This is because ilmenite has a lower tendency of being ground down to finer materials. Consequently there is a lesser need offluid dilution. During the drilling operations excessive wear on different types of equipment was observed. This abrasion was anticipated to be a result of usage of a rather coarse ilmenite material. Although the abrasion was anticipated to be merely a result of the particle size distribution than the material itself, no further field evaluations were conducted until the earlynineties.

The Best Common Ways to Manage Barite Sag in HPHT and Deviated Operations With a Case Study in the Iran Oil Industry

“…The heavy metal content of ilmenite is lower on most components than that of barite. In addition, it is claimed that the bioavailability of the heavy metals is lower in ilmenite than in barite (Fjogstad et al, 2000). Therefore, it is believed to be more desirable to use materials such as ilmenite than barite as weighting agents in drilling fluids.…”

“…Some typical mineral properties of ilmenite and Barite are given in Table 1. Ilmenite was successfully applied in a drilling operation in 1999 (Fjogstad et al, 2000). Barite was used as the weight material on all sections except for one 12 1/4 00 section drilled with water-based drilling fluid in January-February 1999.…”

Effective Ways to Avoid Barite Sag and Technologies to Predict Sag in HPHT and Deviated Wells

“…The heavy metal content of ilmenite is lower on most components than that of barite. In addition, it is claimed that the bioavailability of the heavy metals is lower in ilmenite than in barite (Fjogstad 2000). Therefore, it is believed to be more desirable to use materials like ilmenite than barite as weighting agents in drilling fluids.…”

“…Some typical mineral properties of ilmenite and Barite is given in Table 1. Ilmenite was successfully applied in a drilling operation in 1999 (Fjogstad 2000). Barite was used as the weight material on all sections except for one 12 ¼" section drilled with water based drilling fluid in January-February 1999.…”

Drilling Fluid Affects MWD Magnetic Azimuth and Wellbore Position

“…At the Norne field in the Norwegian Ocean, ilmenite has been tested as weight material 5,6 . In some of the sections some "strange" directional survey results have been identified, which turn out to be caused by the ilmenite-based drilling fluid.…”