High-Resolution Environmental Survey around an Exploration Well Drilled with Formate Brine in the Barents Sea, Norway

Abstract

The present paper gives an overview of the environmental impact of cuttings discharges on the bentic sediments, three years after drilling an exploration well (7122/7–1) with formate brine (mixture of potassium and sodium formate) in Production Licence 229 in the southwestern part of the Barents Sea. Eni conducted a high resolution environmental survey on the physical, chemical and biological conditions of the benthic sediments, in the vicinity of well 7122/7–1 drilled in 2000 in PL229. The cuttings and mud from the well were released to the environment as the drilling operation was conducted before the political decision to restrict the discharge of cuttings and mud from operations using water based mud (WBM) in the Barents Sea¹. The aim of the study was to verify findings in a life cycle assessment (LCA) that had been conducted for formate brine, which concluded with: "The findings of the study indicate that the discharge of moderate amounts of Formate Brines is not likely to lead to potentially significant negative impacts on the marine environment." 2 Samples were collected from 27 stations surrounding well 7122/7–1. Apart from the reference station, all stations were within 500 meters of the well head (reference station about 3 km to the south of the well head). Samples from 22 stations were analysed physically/chemically and 19 stations were analysed biologically, in addition to the reference station. As stations were very close to each other, very high sampling accuracy was of crucial importance. The findings in this study are in line with the conclusion in the LCA as only minor environmental impact in the vicinity of the drilling location was detected. Introduction Eni is the operator of the Goliat field (Production Licence 229), in the sub area "Finnmark West" in the southwestern part of the Barents Sea. Well 7122/7–1 is located 86 km (aerial distance) Northwest of the city of Hammerfest. The water depth in the area is between 370 and 400 m. A map of the area, which also shows all the exploration/appraisal wells drilled in this part of the Barents Sea, along with the prevailing sea currents, is shown in Figure 1. Eni found a petroleum-containing reservoir at exploration well 7122/7–1 in 2000 and a second exploration well (7122/7–2), located approximately 1 km NW of the first well, was drilled during the autumn of 2001. Eni Norge is planning another appraisal well in order to get more information for the field development evaluation. Eni Norge AS (Eni) believes that life cycle assessment (LCA) including environmental considerations should be the basis for mud and cuttings handling. In order to derive an optimal decision support, the environmental impact of different options must be known. Drilling of off-shore petroleum wells on the Norwegian Continental Shelf (NCS) was traditionally conducted with oil-based mud (OBM) which was subsequently released to the environment. Since the release of oil-based cuttings and mud to the environment was restricted to 10 g/kg in 1993 due to environmental considerations, there has been an increased use of WBM. WBM and cuttings from all the sections can be released into the environment on the NCS as long as the hydrocarbon content is less than 10 g/kg, except in the Barents Sea, where only releases from the top-hole section are allowed for the time being as a result of a political decision in 2004–51. The top-hole section is normally defined as the section(s) drilled before the blow out preventor (BOP) is installed. In order to investigate the actual environmental impact of the drilling of an exploration well, Eni initiated a high resolution environmental survey in the vicinity of the Goliat wells in 2003. As only exploratory drilling has been carried out so far, none of the stations have been investigated earlier, but a baseline survey was conducted in the area in 19983. The Eni survey is one of the few surveys that have been conducted in close vicinity to an exploration well, since Norwegian regulations generally only require monitoring around production wells.

Drilling, Completion, and Openhole Formation Evaluation of High-Angle HPHT Wells in High-Density Cesium Formate Brine: The Kvitebjorn Experience, 2004-2006

“…In 2003 an independent consultant carried out a Life Cycle Assessment on formate brines and concluded that " The findings of the study indicate that the discharge of moderate amounts of formate brines is not likely to lead to potentially significant negative impacts on the marine environment" 5 . This finding was supported by ENI Norge who conducted an environmental survey in the vicinity of an exploration drilled in the Barents Sea with formate brine 6 . ENI concluded: "The survey...demonstrates that the environmental impact caused by the discharge of formate brine from a single well is minimal 3 years after the operation".…”

Drilling and Completing Difficult HP/HT Wells With the Aid of Cesium Formate Brines— A Performance Review

“…Formates have a good reputation as shale drilling fluids [32][33][34][35][36] , and cesium formate brine itself has clearly provided good shale stabilization in 14 out of the 16 HPHT wells where it has been used as a drill-in fluid. The hole enlargement through cap-rock shale sections that have been reported in the two Kristin wells are therefore anomalous and need further investigation…”

A Viable Hydrogen Storage and Release System Based on Cesium Formate and Bicarbonate Salts: Mechanistic Insights into the Hydrogen Release Step

“…Furthermore, elevated cesium levels in the environment have not been reported to cause any adverse effects. [32,33] The discharge of cesium in aquatic systemsi sl ikely to be extenuated by dilution, whereas in terrestrial environments sorption of cesium would minimize its bioavailability.C esium formate is not ar eported carcinogen but is known to be am ild eye and skin irritant. Chronic health effects are mainly associated with high repeated oral doses of the compound which are highly unlikely to be as ignificant factor with small-to medium-scale hydrogen storages ystems.…”