Techniques Used To Monitor and Remove Strontium Sulfate Scale in UZ Producing Wells

Abstract

Scale deposition in completion strings is becoming a threatening problem to produce and safely operate wells completed in the Upper ZAKUM (UZ) oil field. Calcite or Calcium Carbonate (CaCO3) scale mostly found in the upper part of the production string, and Celestite or Strontium Sulphate (SrSO4) mostly found in the lower part of the production string, are the common type of scales encountered in Upper ZAKUM producing wells. Injection seawater (rich in Sulphate) and formation water (rich in Strontium ions) mix in the reservoir and/or wellbore under varying conditions resulting into Strontium Sulfate Scale formation in downhole equipment. While CaCO3 scales are possible to be removed by the use of common acids and wireline tools, Strontium Sulphate scale requires special techniques to remove chemically and/or mechanically, and present the most challenges to achieve complete removal.This work will describe ZADCO scale management strategy to monitor and remove Strontium Sulfate scale in Upper Zakum producing wells. A scale prediction simulator is used to identify wells with high scaling risk. Scale Risk Matrix (SRM) is being developed to classify the scale risk in each well. The Chlorides content, the percentage sea water in the produced water, the production rate, the percentage water cut and scaling index are the main parameters that are used to calculate the overall scaling risk for a certain string. The wells classified as high scaling risk wells, are included on a monitoring list for periodical scale checks by running gauge cutters on slickline. Scale samples are collected and sent to the lab for analysis and scale type identification.The category of strings with a scale thickness less than 0.25" are treated with a chemical scale dissolver, the wells containing scale thicker than 0.25" are treated with downhole cleaning tools run on Coiled Tubing.In 2005, ten wells severely scaled with Strontium Sulphate were mechanically treated using Coiled Tubing, Mills and motor, high pressure rotating tool with Sterling Beads* and Polymer as the cleaning fluid. Most of the job objectives were not completely accomplished due to severe hard scaling conditions.

Occurrence and Characterization of Paraffin Wax Formed in Developing Wells and Pipelines

“…A drastic decrease in productivity from 30,000 Barrels of Oil Per Day (bopd) to zero within 24 h was observed in the North Sea Miller field [38]. The Alba field located on the UK continental shelf and the Zakum field located in Abu-Dhabi, are included among the world's largest oil fields where sulphate and carbonate scale were found [39,40]. More information about the composition and characterization of waxy crude oils in different regions is shown in Table 2.…”

Reusable Sensor for Strontium Sulfate Scale Monitoring in Seawater

“…It is well known in the oil industry that strontium ions cause large amounts of scaling on the inner surface of the pipelines leading to a drastic reduction in oil production and huge financial losses [ 17 , 18 , 19 , 20 ]. One of the major challenges of the oil industry is to prevent scale development in the oil production pipelines [ 20 , 21 , 22 , 23 , 24 , 25 ]. This scaling is due to the mixing of injected seawater with the produced water from the well.…”

“…According to the recent fieldwork [ 21 ] in Upper Zakum (4th largest oil field in the world) in Abu Dhabi, it was reported that the main scales present in the oil wells in this field are calcium carbonate (CaCO 3 ) in the upper part of the wells and strontium sulfate (SrSO 4 ) in the lower part of the wells. From the field data and records, the report clearly emphasized the big challenge faced in removing the strontium sulfate scale due to its hardness.…”

Effect of Saline Solution on the Electrical Response of Single Wall Carbon Nanotubes-Epoxy Nanocomposites

“…There have been multiple studies and research conducted on scale monitoring, testing, and optimization of scale inhibitors [1][2][3]. The current industry practice for managing scale programs relies on the determination of scale inhibitor concentration in the scaling brine and then relates this concentration to program performance.…”