Enhancing the life of scale inhibitor squeeze treatments in the oil and gas industry is a major means of increasing productivity. Having an understanding of the route by which inhibitors such as PPCA can adsorb to the rock surface is important in designing new squeeze methodologies. Nanotechnology is emerging as an enabling technology in many fields including medicine, transport and pharmaceutical. Thus far there has been research activity in novel uses of nanotechnology in the oil and gas sector but there is still enormous potential for it to be further exploited. In the squeeze process, where fluids are pushed through the rock pore space, there is potential for nanotechnology to enhance the delivery of species (i.e. placement) and/or to assist in the "binding" of active species to the rock surfaces. It is in this area the current work is focused. In this paper we investigate the adsorption of PPCA (a common scale inhibitor) onto a C-based nanoparticle (CBN). The adsorption of PPCA on the CBN is quantified as a function of time and the concentration of the CBN. Experimental data from Inductively Coupled Plasma (ICP) illustrates a substantial adsorption of PPCA on CBNs comparing to the adsorption of PPCA on the rock. Various concentration ratios of CBNs and PPCA have been tested in dynamic adsorption tests to understand the effects of absorbent and absorbate concentration. The mass of adsorbent was assumed to be key factor in adsorption of PPCA on CBNs; indicative of the number of active sites on the nanoparticle.
Keywords: Nanotechnology, squeeze, PPCA, adsorption
Organosilane has been explored previously as a kaolinite fixing agent, and surface modifier to enhance adsorption of scale inhibitors. Here, self-assembled organosilane films are investigated for their potential to prevent scale deposition directly, that is without the presence of scale inhibitors. Film formation on quartz crystals is analysed using a quartz crystal microbalance, which suggests that different film structures can be created using the same organosilane molecule. Brine tests using singlecrystal quartz coupons coated with organosilane indicate that calcium carbonate scale deposition can be reduced by 66%.
Keywords: adsorption, organosilane, inorganic scale precipitation, self-assembled monolayer, quartz
Sanders, Laura (University of Leeds) | Hu, Xinming (University of Leeds) | Mavredaki, Eleftheria (U. of Leeds) | Eroini, Violette (U. of Leeds) | Barker, Richard (University of Leeds) | Neville, Anne (U. of Leeds)
The formation of calcium carbonate scale and the occurrence of corrosion in CO2-saturated environments in different parts of oil and gas facilities are both phenomena that have been extensively studied. However, to date, very limited work has been carried out on evaluating combined products in a combined scale/corrosion methodology. This paper presents the results from a new combined bulk jar scaling/bubble cell corrosion test. The aim of this project is to investigate the effect of two combined chemicals in a new experimental setup; to study the corrosion and scale interactions which occur simultaneously. Two combined products were assessed at 5 ppm concentration at two temperatures (60ºC and 80ºC) in a CO2-saturated brine. Bulk scale precipitation was monitored using a turbidity meter and the corrosion rate measurements were made using the linear polarisation resistance (LPR) technique. Scale deposition and corrosion mechanisms have been studied using surface analyses. The performance of the two combined products has also been tested to measure: (i) the increase in the induction time of the calcium carbonate formation in the bulk, (ii) the change of the morphology of the crystals and (iii) the formation of a partial protective layer on the sample.
According to this study, the new experimental method has enabled the corrosion and scale deposition on pipeline steel (X65) and the bulk precipitation process to be studied simultaneously. Detailed scale deposition mechanisms on the material surface in the presence of corrosion processes and combined products are addressed from this study.
Keywords: calcium carbonate, scale, corrosion, combined inhibitors
Lean Duplex stainless steels are becoming attractive for applications in oilfield and marine environments due to their economic advantages, very good mechanical properties and relatively good corrosion resistance. However, there is little information about the pitting behaviour of lean Duplex stainless steels in oilfield and marine environments. This paper discusses the tendency for pitting corrosion to initiate through an evaluation of breakdown potentials of lean Duplex stainless steels UNS S32101, UNS S32304, LDX2404, standard Duplex stainless steel UNS S32205 and Austenitic stainless steels, 304L and 316L in aerated 3.5% NaCl and a CO2-saturated oilfield brine solution. Electrochemical measurements were made using a three-electrode electrochemical set up using an Ag/AgCl reference electrode and a platinum counter electrode. The results showed that breakdown potentials are generally higher in aerated 3.5% NaCl than the CO2-saturated oilfield brine solution for all the alloys tested. Lean Duplex stainless steel UNS S32101 and Austenitic stainless steel 304L showed comparable breakdown potentials in both environments while lean Duplex stainless steel UNS S32304 and Austenitic stainless steel 316L also have comparable breakdown potentials. There does not seem to be a universal relationship between Pitting Resistant Equivalent number and breakdown potential for the lean Duplex and Austenitic stainless steels.
Key words: Lean Duplex stainless steels, breakdown potential, aerated 3.5% NaCl, CO2 saturated oilfield brine.
Corrosion and scale deposition are well known problems in pipelines. Corrosion control of carbon steel pipelines requires an understanding of the simultaneous occurrence of both processes. To date there have been few studies demonstrating the interactions between surface scale deposition and corrosion processes. Common methods of controlling corrosion and scale are deploying corrosion and scale inhibitors. However, combined (ComI) are receiving increased attention from industry as their application can significantly reduce chemical costs. Many factors influence the performance of corrosion and scale inhibitors and the influence of supersaturated brines on the surface scale deposition and subsequent effects on corrosion processes are generally not well understood. The work presented describes a range of laboratory tests conducted to assess the influence of different supersaturated brines on corrosion and scale on both inhibited (ComI) and uninhibited systems. Corrosion is measured by conventional electrochemical techniques and surface deposition is assessed using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX). Bulk precipitation is measured by turbidity.
Akbar, Abdulmuhsen (Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds) | Hu, Xinming (Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds) | Wang, Chun (Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds) | Neville, Anne (Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds)
Barker, Richard (Institute of Engineering Thermofluids, Surfaces and Interfaces School of Mechanical Engineering University of Leeds) | Hu, Xinming (Institute of Engineering Thermofluids, Surfaces and Interfaces School of Mechanical Engineering University of Leeds) | Neville, Anne (Institute of Engineering Thermofluids, Surfaces and Interfaces School of Mechanical Engineering University of Leeds) | Cushnaghan, Susan (Shell U.K. Limited)
ABSTRACT Scaling, which is the formation of insoluble inorganic solids, is a major problem in water treatment plants and in the oil industry. Millions of dollars are spent each year to prevent the occurrence of scale. Calcium carbonate (CaCO3) and barium sulfate (BaSO4) are common types of scale encountered in these sectors. Scale predictions are typically based on thermodynamics and tend not to give a time-based quantification of surface scale growth. Recent work clearly demonstrated that scale deposition and precipitation are two different processes and that their rates should be evaluated separately. This paper initially compares the kinetics of CaCO3 precipitation in the bulk and deposition on the surface of austenitic stainless steel (316L) at 24°C and 70°C under a controlled turbulent flow regime. Secondly, precipitation and deposition data are combined to obtain the first kinetic surface deposition model giving a scale thickness in millimetres per year as a function of the saturation index for CaCO3 scale at these two temperatures. Experiments were performed using a Rotating Cylinder Electrode (RCE) device. Several techniques, such as Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma (ICP), were used to investigate the precipitation in the bulk and deposition of CaCO3 scale on the stainless steel surface. The paper discusses the value and limitations of the model and how it can be used to build the understanding of surface scale deposition. INTRODUCTION Scaling is a major issue for the oil industry. There are several different types of scale such as calcium sulfate and barium sulfate; however, the most common is undoubtedly calcium carbonate.1, 2 The water used to enhance oil recovery brings large amounts of ions, such as calcium ions, from the carbonates reservoir. The water composition, in addition to the elevated temperature, promotes scale formation.