Downhole Scale Management in Gorm, Dan, and Halfdan, and Implications to Industry Trends

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThree oil producing fields in the Danish sector of the North Sea, Gorm, Dan and Halfdan, have been assessed for downhole scale control. All three fields have water injection. To date downhole scaling has not been perceived as a significant production problem in these fields. This paper presents the results of a review of the well service history for each well in the three fields which identified when and where scales had been encountered and estimated the impact of scale on well intervention operations. A thermodynamic equilibrium model for mineral solubilities was used to assess the scaling tendencies of sulphate and carbonate scales from bottom hole to wellhead. The observational data for downhole scale has been compared with the scaling predictions and a risk assessment for carbonate and sulphate scales developed for each well. The implications of this study on industry trends are discussed.

Classification of and changes within formation water types in Danish North Sea Chalk: A study of the Halfdan, Dan, Kraka and Valdemar oil reservoirs

“…They found that the HCO − 3 concentration is approximately 400 mg/L for the Dan and Halfdan fields. [1] Hence, this value is used for reservoir conditions. (Also, we use the reservoir pressure reported here.…”

“…One which has higher pressure and temperature. [57] • Reservoir conditions (from [1]): − 17 000 kPa , 70 ∘ C, 400 mg/L HCO − 3 . Valdemar (from [57]): 37 000 kPa, 86 ∘ C, 400 mg/L HCO − 3 .…”

“…In many oil fields in the Danish North Sea, including the Halfdan field, scale has proven to be a significant risk in some wells. [1] The Ba 2+ and Sr 2+ concentrations and even slight variations therein are very important for the monitoring and mitigation of the potential formation of insoluble scales in the presence of SO 2− . [5] SrSO 4 and BaSO4 are critical when formed in the wellbore area, while they are less harmful overall when deposited in the reservoir.…”

“…Hence, it is not expected to be present in the wellbore area, which is the most critical place. [1] The Extended UNIQUAC calculations are carried out with the mean compositions and the P10 compositions of the EMs. The observed trends are similar for the two modelled compositions; they are simply stronger with the P10 compositions (Supplementary Material Table 4 and 6).…”

“…Produced water from oil production wells is routinely analyzed for its ionic composition, in order to monitor the well performance and track potential scale precipitation and corrosion in the wells. [1,2] Certain detrimental scales in the wells and installations are an operational risk and very costly to remove, and the potential precipitation of these is dependent on the concentrations of trace ions in the flowing water. Consequently, an interest in monitoring the chemical composition of the produced water reliably has been existing from the very early stage of production.…”