Evaluation of a New Treatment to Remove Calcium Sulfate Scale: Lab Studies and Field Application (original) (raw)
Related papers
Petroleum Science, 2016
The formation of mineral scale is a complex problem during the oilfield operations. Scale inhibitors are widely used to prevent salt precipitation within reservoirs, in downhole equipment, and in production facilities. The scale inhibitors not only must have high effectiveness to prevent scale formation, but also have good adsorptiondesorption characteristics, which determine the operation duration of the scale inhibitors. This work is focused on the development of a new scale inhibitor for preventing calcium carbonate formation in three different synthetic formation waters. Scale inhibition efficiency, optical density of the solution, induction time of calcium carbonate formation, corrosion activity, and adsorption-desorption ability were investigated for the developed scale inhibitor. The optimum concentration of hydrochloric acid in the inhibitor was determined by surface tension measurement on the boundary layer between oil and the aqueous scale inhibitor solution. The results show that the optimum mass percentage of 5 % hydrochloric acid solution in the inhibitor was in the range of 8 % to 10 %. The new scale inhibitor had high efficiency at a concentration of 30 mg/L. The results indicate that the induction period for calcium carbonate nucleation in the presence of the new inhibitor was about 3.5 times longer than the value in the absence of the inhibitors. During the desorption process at reservoir conditions, the number of pore volumes injected into the carbonate core for the developed inhibitor was significantly greater than the volume of a tested industrial inhibitor, showing better adsorption/desorption capacity.
Mitigation of Calcium Sulfate Scale Deposition During Fracturing Treatments
Day 3 Tue, October 15, 2019, 2019
Calcium sulfate scale precipitation is a challenge especially during stimulation treatments. The main objective of this study is to mitigate calcium sulfate precipitation during fracturing treatment. With high sulfate content in source/mixing water up to 2,000 parts per million (ppm) and excessive of total dissolved solids (TDS) formation water that can reach 60,000 ppm calcium.An experimental study was conducted at the reservoir downhole temperature of 280°F to evaluate the formation water compatibility with source water wells used for fracturing fluids. The sulfate content varied in the fracturing fluids up to 2,000 ppm. This paper addresses: the scaling tendency of water-water interaction; the efficiency and minimum inhobitor concentration of three commercial calcium sulfate scale inhibitors; the stability of high sulfate fracturing fluids at 280°F (138°C) with scale inhibitors.This study indicated: water-water compatibility tests reinforce the mineral risk assessments findings f...
Oilfield scale formation and chemical removal: A review
Journal of Petroleum Science and Engineering, 2018
In oil and gas industry operations, scale deposition on the surface and subsurface production equipment can cause different problems such as formation damage, loss in production, pressure reductions, and premature failure of down hole equipment. Due to geochemical processes between injection water, connate water and rock, the complex composition of reservoir fluids make it difficult to control the inorganic scale formation. Carbonate (calcium), sulfide (iron, zinc), and sulfate (calcium, barium, strontium) scales are more common in oilfield applications. The scale formation depends on several factors that include, but not limited to, temperature, pressures, solution saturation and hydrodynamic behaviour of the flow. This paper reviews different types of scales that are common in oil and gas production operations, their sources and formation mechanisms. The focus of this review is on the different chemicals that are used for the removal of different scales. Hydrochloric acid is one of the classical chemicals used since for most of the mineral scales are soluble in HCl. However, HCl is not environmentally-friendly and causes corrosion and could be very expensive particularly in high-temperature conditions due to the need of using many additives to reduce corrosion. This review discusses several alternatives to HCl that are more environment-friendly in removing oilfield scale deposits. These alternatives are mainly organic acids and chelating agents which have been successfully applied in different fields.
Inhibition of Calcium Sulfate and Strontium Sulfate Scale in Waterflood
SPE Production & Operations, 2010
Summary One of the most common methods of preventing downhole and topside mineral-scale formation in oil fields is through the use of chemical-scale inhibitors. Several aspects of the brine composition may affect the performance of the various scale inhibitors used in oilfield applications. This study was conducted to investigate the permeability reduction caused by deposition of calcium sulfate (CaSO4) and strontium sulfate (SrSO4) in Malaysian sandstone and Berea cores from mixing injected Malaysian seawaters (SW) (Angsi and Barton) and formation water (FW) that contain a high concentration of calcium and strontium ions at various temperatures (50 to 95°C) and differential pressures (75 to 200 psig). Scale-inhibition efficiency was determined in both the bulk jar and the core tests by using scale inhibitors methylene phosphonic acid (DETPMP), polyphosphino carboxylic acid (PPCA), and phosphorus-based scale inhibitor (PBSI) at various temperatures (50 to 95°C) and concentrations. T...
Performance Evaluation of Biodegradable Oilfield Scale Inhibitors for Calcium Carbonate Scales
Scale formation is a serious oil field problem that is detrimental to water injection systems. The most common means ofreducing and preventing scale deposition is through the use of scale inhibitors. The research is aimed at evaluating two environmentally friendly scale inhibitors, polyaspartic acid (PAS) and polymer of maleic acid (PMA) origin; in terms of their inhibition performance on CaCO 3 scaling water. Both biodegradable scale inhibitors (PAS and PMA) were evaluated through compatibility test, thermal stability at 130ºC evaluation and static jar test. Comparability tests perfomed at temperatures of 25 o C and 90 o C for the PAS and PMA,did not indicate any precipitationat the various scale inhibitors concentrations studied. The result of the thermal stability tests on the two scale inhibitors at 130 o C indicated that the two inhibitors PAS and PMA were thermally stable, since no precipitates were formed. Accordingly, the scale inhibition performanceevaluation was carried out using static jar test. The scale inhibition efficiency for PAS on calcium carbonate scaling water was 87% with a treatment dose of 80 ppm and at 80 º C, while at the same treatment dose of 80ppm resulted in 69% scale inhibition efficiency at 90 º C. Also, for PMA the scale inhibition efficiency on calcium carbonate scaling waterwas 70% with a treatment dose of 80ppm and a80 º C while at the same treatment dose of 80ppm a61% scale inhibition efficiency was achievedat 90 º C. Finally, based on set criteria, the PAS scale inhibitor was adjudged to have passed all evaluation criteria at 80ppm, thereby proving more effective in performance than the PMA scale inhibitor.
Scale Deposits in Porous Media and Their Removal by Edta Injection
2008
Formation damage has been observed in several oil reservoirs and production equipment in Iranian oil fields. Laboratory and field testing confirmed that the primary cause of damage was the build-up of calcium carbonate, calcium sulfate and strontium sulfate scale either in the perforation tunnels or in the formation sandstone nears the wellbore. Conventional acid treatments could dissolve this scale, but scale precipitation from the spent acid caused rapid productivity decline. A scale removal treatment with Na2H2EDTA has been developed that can effectively dissolve scale and chelate the dissolved metal ions. Chelation of the dissolved scale prevents scale reprecipitation. This study describes the results of an experimental and theoretical study on the removal of formation damage resulting from scale formation in porous media. An experimental investigation was undertaken to look into the possible causes of the injectivity loss in a typical Iranian oilfield. Sets of experimental inve...
SPE Production & Facilities, 2003
Summary Using chemical scale inhibitors is one of the most common methods of preventing downhole and topside mineral scale formation in oil fields. Several aspects of the brine composition may affect the performance of the various scale inhibitors. In this paper, we focus on the roles of calcium and magnesium ion concentrations. The calcium concentration in a particular reservoir and in the inhibitor slug often determines the extent to which the inhibitor species is retained in the near-wellbore area (i.e., on its adsorption or precipitation behavior). What is less well understood is the effect of divalent cations on the inhibition process itself. Common ion effects are well known; however, for pentaphosphonate inhibitor species (e.g., DETPMP), significant improvements in inhibition efficiency have been reported by increasing the calcium concentration in the solution. In this paper, we expand significantly on such observations. The effect of calcium and magnesium cation concentratio...
A potential mechanism for part of the production decline observed in the Prudhoe Bay field is siderite (iron carbonate) scale deposition. This laboratory investigation focused on evaluating the effect of the existing downhole scale inhibitor program on the proposed siderite formation damage mechanism. A tube block test was employed to generate iron carbonate and evaluate commercial products for its inhibition. This study indicates that the current inhibition program for barium sulfate and calcium carbonate is not protecting against damage by iron carbonate deposition. The other products tested were also ineffective. Furthermore, precipitation of the scale inhibitors by iron(lI) is suspected. There is no field evidence of damage from this precipitation with the current inhibition program.
Scale formation is one of the most serious oil field problems that inflict water injection systems. This study was conducted to investigate the permeability reduction caused by deposition of scale in oil field water where contained high concentration of calcium ion at various temperatures (40, 60, 80 and 95 °C). The aim of this work is study the prevention or minimizing of scale formation in oil field by using economic and good performance inhibitor. The scale inhibitor phosphonate type (DTPMP) was conducted at low and high temperatures, was shows a good performance at low concentrations 3 to 20 ppm. Static test was carried out to demonstrate the best concentrations of scale inhibitors at different temperatures. The Dynamic test has also done for the sample by using dynamic scale rig test at a temperature of 75°C and injection rate of 2 liter per hour for sample (scaling solution) to determine the efficiency of scale inhibitor Diethylene triamine-pentamethylene phosphonic acid (DTPMP) at injection rates of (3, 5, 7, 10, and 20ppm). From the both static and dynamic experiments we conclude that the performance of scale inhibitor (DTPMP) is effective in preventing calcium carbonate CaCO 3 scale, where it has achieved efficiency at 40, 60, 80 and 95 o C was 100, 98.20, 94.83 and 88.50% respectively, at concentration 10ppm. The performance of scale inhibitor considered an effective inhibitor where the minimum performance was 60.00 – 96.23% at low concentration (3 ppm); this is considered acceptable performance and economic as scale inhibitor in the oil fields water.