Phosphino-polycarboxylic Acid Research Articles

Interactions of common scale inhibitors and formation mineral (calcium carbonate): Sorption and transportability investigations under equilibrium and dynamic conditions

Formation and deposition of mineral scales pose a serious threat to the safety and integrity of oilfield operations. Scale inhibitor chemicals have been widely employed to control scale threat and enhance production efficiency. The inhibitor-formation mineral interaction together with inhibitor transport behavior play significant roles in the design and optimization of oilfield inhibitor treatment. However, limited studies have been reported to investigate the principles dictating the inhibitor-mineral interaction under both equilibrium and dynamic conditions. Moreover, there are few studies focusing on the inhibitor transport at a lower inhibitor concentration. In this study, a systematic evaluation of the physicochemical nature of inhibitor-formation mineral interactions was conducted with a focus on lower inhibitor concentrations (below 50 mg L−1) by adopting two common oilfield inhibitors of diethylenetriamine pentamethylene phosphoric acid (DTPMP) and phosphino-polycarboxylic acid (PPCA). The formation mineral employed in this study is calcium carbonate (calcite). Both equilibrium and the kinetics aspects of inhibitor sorption behavior have been studied experimentally via static batch and dynamic column apparatus. It was found that the adsorption capacity of calcite for DTPMP is higher than that of PPCA. Laboratory fixed-bed column transport experiments were carried out at different physicochemical conditions of initial inhibitor concentration, ionic strength, temperature, flow rate and calcite particle size. Results indicate that an increase in both DTPMP and PPCA concentration can expedite inhibitor transport and a high initial DTPMP concentration could significantly affect the retention of DTPMP in the calcite porous medium. Ionic strength can result in a higher transportability in calcite medium for both inhibitors. Change in temperature has no significant impact on inhibitor transport. The flow rate has a considerable influence on the dispersion coefficient due to elevated mechanical dispersion at a higher flow rate for DTPMP. The calcite particle size can also impact inhibitor adsorption due to the change in surface area. Furthermore, adsorption of PPCA can subject the calcite surfaces more hydrophilic than DTPMP, which can affect the mobility of inhibitor in calcite medium. Atomic force microscopy characterization results confirmed that the wettability of calcite was increased through adsorption of DTPMP and PPCA inhibitor. This study provides deep insights into the sorptive behavior and transportability of DTPMP and PPCA inhibitors in calcite porous medium.

Crystal growth inhibition of gypsum under normal conditions and high supersaturations by a copolymer of phosphino-polycarboxylic acid

Scale formation is a bottleneck of most industrial and domestic water equipment, in particular, of oilfield water systems. Therefore, high-performance and environmentally-benign chemical scale inhibitors are highly needed. Phosphino-polycarboxylic acid (PPCA) is a low-in-phosphorous scale inhibitor with high inhibition efficiency, but its synthesis and performance analyses have been rarely disclosed. In this work for the first time, a PPCA copolymer is synthesized by a simple method based on free radical polymerization of acrylic acid and phosphinic acid monomers and directly employed for gypsum scale inhibition. The formation of PPCA was verified by FTIR and 31PNMR spectroscopies, and then its inhibition performance was evaluated by the complexometric determination of the Ca2+ concentration. The PPCA (2.5 ppm) showed 100% inhibition efficiency at a saturation index of 0.31 at the room temperature and without pH regulation after 24 h with practically no detectable gypsum crystallites even after two months, while the commercial ATMP showed a low inhibition efficiency of 30%. The Field Emission Scanning Microscopy (FESEM) images of the PPCA-inhibited and uninhibited samples revealed that the typical gypsum microfibers are distorted and reduced in size significantly in the inhibited sample. At a still higher saturation index of 1.47 (saturation ratio of 10), the inhibition efficiency of PPCA reduced to 16% and 24% for two dosages of 2.5 and 10 ppm which was attributed to the higher ion activity coefficients at the extremely high ionic strength, and hence, a much higher thermodynamic driving force. The rate constants for these two high supersaturation conditions and low PPCA dosages were also calculated and discussed.

Building a Fundamental Understanding of Scale-Inhibitor Retention in Carbonate Formations

Summary The development of effective scale-inhibitor (SI) squeeze treatments remains a challenge for carbonate reservoirs because of their substantial chemical reactivity with the SI. This in turn might potentially lead to uncontrolled SI precipitation and induced formation damage. This work takes a systematic approach to understanding the retention mechanisms of SI in carbonate formations with respect to the detailed carbonate-formation mineralogy, type of SI, and reservoir conditions in the absence of oil. Static adsorption/compatibility experiments, described previously as apparent adsorption tests (Kahrwad 2008), were performed to evaluate the areas of different retention mechanisms [pure adsorption (Γ) and coupled adsorption/precipitation (Γ/Π)] of different SI species in brine. Experiments were conducted for five SIs at various conditions: initial pH values, mineralogical compositions (calcite, limestone, and dolomite), and temperatures. The SI species used in this study included a phosphonate [di-ethylene tetra-amine penta (DETPMP)], a phosphate ester [polyhydric alcohol phosphate ester (PAPE)], and three polymeric SIs [polyphosphino carboxylic acid (PPCA), P-functionalized copolymer (PFC), and sulfonated polyacrylic acid copolymer (VS-Co)]. All precipitates were studied using environmental scanning electron microscopy/energy dispersive X-ray (ESEM/EDX) and particle-size analysis (PSA). The overall results from these coupled Γ/Π experiments are as follows: For the polymeric SIs (PPCA, PFC, and VS-Co), the highest retention levels were observed at low pH for all carbonate substrates, because of the increase in divalent cations calcium and magnesium (Ca2+ and Mg2+, respectively) available from rock dissolution for SI–M2+ ions (divalent cations) precipitation. For DETPMP and PAPE SIs, the retention level was greatest at higher pH values, because the SI functional groups were more dissociated and, hence, available for complexation with M2+ ions. The polymeric VS-Co predominantly showed pure adsorption with only a low amount of precipitation (Γapp ≈ 1.2 mg/g) in contact with the dolomite substrate. This is because of the presence of sulfonate groups (low pKa). For polymeric inhibitors, the retention level (Γapp) was highest on calcite (highest relative calcium content), followed by limestone and dolomite. DETPMP and PAPE SIs showed the highest retention levels on dolomite (higher final solution pH and more SI dissociated), followed by limestone and calcite. For all SI species, higher retention (more precipitation, Π) was observed at elevated temperatures. At lower temperatures, an extended region of pure adsorption was observed for all SIs. The information presented in this study will be helpful in SI product selection on the basis of mineralogy and reservoir conditions. As a consequence, longer squeeze lifetimes and improved efficiency of SI deployment in carbonate reservoirs can be achieved. In addition, this study provides valuable data for validating models of the SI/carbonate/Ca/Mg system that can be incorporated into squeeze design simulations.

Molecular dynamics simulation of the effect of ions in water on the asphaltene aggregation

In this study, the effect of aqueous ions and sediment inhibitors on asphaltene aggregation was investigated. The effect of NaCl, MgCl2 and CaCl2 salts on three asphaltene models of M1, A1 and modified Yen and also the combined effect of two different inhibitors and these salts have been investigated by using molecular dynamics (MD). The results showed that due to presence of Na+, Mg2+ and Ca2+ cations, asphaltene aggregation has an ascending, descending, ascending trend, respectively and the amount of asphaltene aggregation in the A1 model due to having more electronegative atoms is higher than the other two. In the presence of diethylene triamine-penta methylene phosphonic acid (DETPMP) and poly-phosphino carboxylic acid (PPCA) inhibitors, the amount of sediment was reduced in all three models of asphaltene, but the asphaltene aggregation with the presence of DETPMP inhibitor significantly decreases due to the delay in the growth of crystals.

The Effect of pH and Mineralogy on the Retention of Polymeric Scale Inhibitors on Carbonate Rocks for Application in Squeeze Treatments

Summary The bulk “apparent-adsorption” behavior (Γapp vs. Cf) of two polymeric scale inhibitors (SIs), polyphosphino carboxylic acid (PPCA) and phosphorus-functionalized copolymer (PFC), onto carbonate mineral substrates has been studied for initial solution pH values of 2, 4, and 6. The two carbonate minerals used, calcite and dolomite, are much more chemically reactive than sandstone minerals (such as quartz, feldspars, and clays), which have already been studied extensively. In nearly all cases, precipitates formed at higher SI concentrations were caused by the formation of sparingly soluble SI/calcium (Ca) complexes. A systematic study has been performed on the SI/Ca precipitates formed by applying both environmental scanning electron microscopy energy-dispersive X-ray (ESEM-EDX) analysis and particle-size analysis (PSA), and this identifies the morphology and the approximate composition of the precipitates. For PPCA, at all initial solution pH values, regions of pure adsorption (Γ) (PPCA < 100 ppm) and coupled adsorption/precipitation (Γ/Π) are clearly observed for both calcite and dolomite. PFC at pH values of 4 and 6 also showed very similar behavior, with a region of pure adsorption (Γ) for PFC < 500 ppm and a region of coupled adsorption/precipitation (Γ/Π) above this level. However, the PFC/calcite case at pH = 2 showed only pure adsorption, whereas the PFC/dolomite case at pH = 2 again showed coupled adsorption/precipitation at higher PFC concentrations. For the SIs on both carbonate substrates, precipitation is the more dominant mechanism for SI retention than adsorption above a minimum concentration of approximately 100 to 500 ppm SI. The actual amount of precipitate formed varies from case to case, depending on the specific SI, the substrate (calcite/dolomite), and the initial pH (pH = 2, 4, and 6). Although the qualitative behaviors of both PPCA and PFC were similar on both carbonate substrates, the apparent adsorption of PPCA was higher on calcite than on dolomite, and the apparent adsorption of PFC was higher on dolomite than on calcite. We discuss here how these observations are related to the reactivity of the different carbonate minerals, the resulting final pH (which affects the dissociation of the SI), the Ca-SI binding, and the solubility of the resulting complex.

Adsorption of polyphosphinocarboxylic acid (PPCA) scale inhibitor on carbon nanotubes (CNTs): A prospective method for enhanced oilfield scale prevention

A scale inhibitor ‘squeeze’ treatment is used in the oil and gas industry as a control measure to reduce the risk of mineral scale precipitation and deposition in the near-wellbore rock formation and associated installations. One of the determining factors in a successful squeeze job is the potential of formation rock to adsorb scale inhibitor (SI); the higher the adsorption, the better the treatment. This paper investigates the potential of employing carbon nanotubes (CNTs) to increase the adsorption of a common SI (polyphosphinocarboxylic acid, PPCA) on formation rock as part of a new methodology forming a ‘Nanotechnology-Assisted Squeeze Treatment’ (NAST). The focus here is assessing the adsorption potential of PPCA on CNTs for the purpose of creating a longer-lasting squeeze treatment. Analyses using various techniques including Transmission Electron Microscopy (TEM), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Thermogravimetric Analysis (TGA) and Raman Spectroscopy are presented, and results indicate that up to 180mg/g of PPCA adsorbed on CNTs, with strong bonding, which is significantly higher than the 1mg/g adsorption of PPCA on crushed formation rock. Adsorption of PPCA decreases with increasing temperature of the solution, indicating an exothermic reaction. The impact of water salinity on adsorption is also considered, with calcium producing a positive effect on adsorption and sodium the opposite. It is also illustrated that a good dispersion of CNTs in the solution can dramatically increase the adsorption due to the exposure of higher surface area to PPCA in the solution. The influence of using CNTs on adsorption of SI onto internal surface of sandstone rock were evaluated using coreflood tests with simplified brines. The results demonstrate the potential of employing CNTs to increase adsorption of SI in squeeze treatments and possibly to improve the squeeze treatment lifetime.

Phosphino-polycarboxylic acid modified inhibitor nanomaterial for oilfield scale control: Synthesis, characterization and migration

Abstract A facile synthesis approach is reported to prepare scale inhibitor nanomaterial for oilfield scale control. The presence of a polymeric scale inhibitor can considerably change the morphology of the nanomaterial with a reduced particle size and an enhanced particle stability. In addition, the presence of electrolyte and sonication methods can impact the morphology and stability of the nanomaterial as well. Laboratory transport experiments suggest that the inhibitor nanomaterial has the future potential for oilfield mineral scale control. This is the first report of the synthesis and characterization of a template-free scale inhibitor nanomaterial combining both phosphonate and polymeric scale inhibitors.

Kinetics study of barium sulphate surface scaling and inhibition with a once-through flow system

The deposition and subsequent growth of inorganic scale on completion equipment is a major problem within the oil and gas industry. An in-situ flow cell was designed to investigate barium sulphate surface fouling on stainless steel. The set-up allows real-time analysis of the formation of scale as well as following various scaling parameters such as the surface coverage or number and size of crystals growing on the surface. The experimental results were fitted to a diffusion-controlled crystallization based model. The effect of PolyPhosphinoCarboxylic Acid (PPCA) scale inhibitor on the growth of crystals was studied and showed that the Minimum Inhibition Concentration (MIC) is different for the surface and bulk solution. The results show that the inhibition mechanism was controlled by the mass transport of scale inhibitor molecules to the active sites of the growing crystals.

Fast evaluation of inhibitors for calcium carbonate scale based on pH continuous measurements in jar test at high salinity condition

Scale formation from calcium carbonate deposition is a major drawback in many industrial facilities, including oil and gas industry, leading to obstruction problems then causing productivity reduction and economic loss. Several anti-scalant formulations, known as inhibitors, are used to control CaCO3 deposition. The evaluation of inhibitors performance is a time-consuming challenge. In the present work a fast approach for evaluation of inhibitor towards calcium carbonate scale controlling is proposed based on continuous pH measurement under jar test condition. Two commercial inhibitors, phosphino polycarboxylic acid (PPCA), usually regarded as a nucleation inhibitor, and diethylenetriamine pentamethylene phosphonic acid (DETPMP), normally considered a growth inhibitor, were evaluated. It was possible to assess their efficiency at same concentration level (5.0ppm), and DETPMP was the one presenting a better performance at the investigated conditions. The main mechanism of action of each inhibitor was also recognized by this methodology.

Phosphino-polycarboxylic acid modified inhibitor nanomaterial for oilfield scale control: transport and inhibitor return in formation media

Evaluation of the transport and return behavior of phosphino-polycarboxylic acid modified scale inhibitor nanomaterial for oilfield mineral scale control.

Sorption Study of ?-ALO(OH) Nanoparticle-Crosslinked Polymeric Scale Inhibitors and Their Improved Squeeze Performance in Porous Media

Summary Polymeric scale inhibitors are widely used in the oil and gas field because of their enhanced thermal stability and better environmental compatibility. However, the squeeze efficiency of such threshold inhibitors, not only polymeric scale inhibitors but also phosphonates, is typically poor in conventional squeeze treatment. In this research, nanoparticle (NP)-crosslinked polymeric scale inhibitors were developed for scale control. Nearly monodispersed boehmite [γ-AlO(OH)] NPs with average size of 2.8 nm were synthesized and used to crosslink sulfonated polycarboxylic acid (SPCA). Crosslinked AlO(OH)-SPCA nanoinhibitors were produced and developed to increase the retention of SPCA in formations by converting liquid-phase polymeric scale inhibitors into a viscous gel. Study of sorption of SPCA onto AlO(OH) NPs under different pHs with and without assistance of Ca2+ was discussed. In addition, study of sorption of various types of scale inhibitors [SPCA; phosphino-polycarboxylic acid (PPCA); and diethylenetriaminepentatakis(methylene phosphonic acid) (DTPMP)] onto AlO(OH) NPs was performed. Squeeze simulation of neat 3% SPCA, AlO(OH) (3%)-SPCA (3%) NPs, and AlO(OH) (3%)-SPCA (3%)-Ca NPs was investigated. The results showed that the addition of Ca2+ ions improves the squeeze performance of SPCA, and the normalized squeeze life (NSL) of such material (8,952 bbl/kg) was improved by a factor greater than 60 compared with that of SPCA alone (152 bbl/kg).

New methodology based on static light scattering measurements for evaluation of inhibitors for in bulk CaCO3 crystallization

In the present work a new procedure for evaluation of scale inhibitor for calcium carbonate is proposed based on continuous measurement of particle size distribution by laser diffraction technique and simultaneous pH recording. From data obtained during real-time monitoring of the homogeneous nucleation and growth of CaCO3 particles formed in the bulk phase after the addition of carbonate ions to synthetic formation water (AF-W2), it was possible to evaluate the performance of four inhibitors classified in two groups: phosphonates (ethylenediamine tetramethylene phosphonic acid, EDTMP; diethylenetriamine pentamethylene phosphonic acid, DETPMP) and polymeric inhibitors (phosphino poly carboxylic acid, PPCA; polyvinyl sulfonate, PVS). The comparative bulk crystallization inhibition efficiency for the evaluated inhibitors, under the experimental conditions used in this work, increases in the following order: EDTMP<DETPMP<PVS≅PPCA. Moreover, this methodology allowed the deduction of the main mechanism of their inhibiting action: nucleation inhibition or crystal growth retardation.

Synthesis and Size Control of Monodispersed Al-Sulfonated Polycarboxylic Acid Nanoparticles and Their Transport in Porous Media

Summary Sulfonated polymers are used in the oil field for scale inhibition. In this study, Al-sulfonated polycarboxylic acid (Al-SPCA) hybrid nanoparticles (NPs) were prepared by taking an environmentally friendly approach. The particle size of these materials was controlled at approximately 80 nm by applying hydrothermal synthetic methods with urea as a slow-neutralization agent. Reaction parameters (e.g., concentration of salt solution, reaction time, urea concentration, and ionic strength) were investigated to optimize NP synthesis. The mobility of Al-SPCA hybrid NPs decreases dramatically in a 1% (wt/wt) KCl solution. With phosphinopolycarboxylic acid (PPCA) as a dispersant, NPs were well-suspended in a 1% KCl solution. Absorption of PPCA by hybrid NPs increases their negative surface charge and decreases particle deposition. The retention and flowback performance of hybrid NPs was compared with the neat-chemical-squeeze simulation in ground-core-column experiments. The results show that the slow release of sulfonated polymer from solid hybrid NPs in a porous medium may have potential inhibitor-treatment application in the oil field.

The Effects of Barium Sulfate Saturation Ratio, Calcium, and Magnesium on the Inhibition Efficiency—Part II: Polymeric Scale Inhibitors

Summary In oilfield-produced waters, the barite mineral-scaling problem is a "moving target" because the seawater/formation-water (SW/ FW) mixing ratio is constantly changing. Therefore, the barite saturation ratio (SR), the yield of barite precipitate, and molar ratio Ca2+/Mg2+ in the produced waters are all evolving over time. This paper describes the effects of SR and molar ratio Ca2+/ Mg2+ on the barium sulfate inhibition efficiency (IE) of nine polymeric scale inhibitors (SIs): phosphino poly carboxylic acid (PPCA); maleic acid ter-polymer (MAT)—a green SI; sulfonated PPCA (SPPCA); phosphino methylated polyamine (PMPA)—a poly-phosphonate; a generic P-functionalized copolymer (PFC); polyvinyl sulfonate (PVS); vinyl sulfonate acrylic acid copolymer (VS-Co); and cationic ter-polymers A and B (CTP-A and CTP-B). The behavior for polymers is compared with similar results for phosphonate SIs (Shaw et al. 2010). IE experiments were carried out for a wide range of SW/FW compositions (i.e., SR and molar ratio Ca2+/Mg2+ varying). The minimum-inhibitor-concentration (MIC) levels of these polymeric SIs sometimes correlate with the level of SR, but not always, which is because of Ca2+ and Mg2+ effects. When experiments were repeated but the produced-brine molar ratio Ca2+/Mg2+ was fixed, MICs always correlate with the level of SR for all nine polymers studied. However, it was observed that for SIs PPCA, MAT, and PFC, the base-case MICs (i.e., molar ratio Ca2+/Mg2+ varying) were less than the fixed-case MICs (molar ratio Ca2+/Mg2+ fixed), whereas in testing SPPCA, PMPA, PVS, VS-Co, and both the cationic terpolymers, the converse is true (i.e., the fixed-case MIC is less than the base-case MIC). It has been demonstrated conclusively that the high [Ca2+] in the fixed-case tests causes some SI precipitation with brine Ca2+ when PPCA is being evaluated (as PPCA-Ca). Sulfonate functional groups present on polymeric SI molecules may help to prevent such incompatibility problems encountered with brine Ca2+ (e.g., SPPCA does not precipitate as SPPCA-Ca). Low levels of brine calcium (e.g., approximately 500 to 700 ppm) can be very beneficial to the IE performance of PPCA. However, when the [Ca2+] reaches a certain level (approximately 1,000 ppm or higher), this causes some precipitation of a Ca–PPCA compound. It has been illustrated that low-to-moderate Ca2+ levels are often best, and it is concluded that this is why SIs PPCA, MAT, and PFC perform better under base-case experimental conditions (lower Ca2+ mix). It has been illustrated that PMPA behaves remarkably similarly to conventional phosphonate SIs with regard to Ca2+ and Mg2+. In fact, the behavior of PMPA suggests that it is not polymeric in nature. PVS, VS-Co, and both the cationic ter-polymers are mildly affected by divalent ions Ca2+ and Mg2+, with the latter being affected more than PVS because of the presence of carboxylate functional groups.

Inhibition of barium sulfate scale at high-barium formation water

One of the most common methods for preventing scale formation is through the use of scale inhibitor. This study was conducted to investigate the permeability reduction caused by deposition of barium sulfate in Malaysian sandstone and Berea cores from mixing of injected Malaysian seawaters (Angsi and Barton) and formation water that contained high concentration of barium ion at various temperatures (50–95°C) and differential pressures (75–200psig). Scale inhibition efficiency was determined in both the bulk jar and core tests by using scale inhibitors Methylene Phosphonic Acid (DETPMP), Poly-Phosphino Carboxylic Acid (PPCA), and Phosphonate-based scale inhibitor (PBSI) at various temperatures (50–95°C) and concentrations. The results showed that a large extent of permeability damage was caused by barium sulfate that deposited on the rock pore surface. At higher temperatures, the rate of BaSO4 precipitation decreases since the solubility of BaSO4 increases with increasing temperature. At 60°C temperature, PPCA showed very efficient BaSO4 inhibition effect where it reduced most amount of BaSO4 compared to the DETPMP and PBSI inhibitors.

Additive-Driven Dissolution Enhancement of Colloidal Silica. 1. Basic Principles and Relevance to Water Treatment

The effect of various chemical additives (small molecules and polymers) on the dissolution of two kinds of colloidal silica (Aerosil 200 and laboratory-synthesized, SSD) is systematically studied at pH 10. The silica scale dissolvers tested are 5-carboxybenzotriazole (CBZT), amino-tris(methylene phosphonic acid) (AMP), a phosphino-polycarboxylic acid (PPCA), diethylenetriamine pentacarboxylic acid (DETPA), a proprietary polymer (Genesol 40), poly(acrylic acid) (PAA), ethylenediamine-tetrakis(methylenephosphonic acid) (EDTMP), phosphonobutane-1,2,4-tricarboxylic acid (PBTC), sodium metaborate, and N-phosphonomethylimino-diacetic acid (PMIDA). Of the polymeric additives only Genesol 40 shows some dissolution activity, dissolving ∼280 ppm silica at 10 000 ppm dosage after 72 h. PBTC and DETPA are the best-performing additives of all those tested. PBTC is effective even at the 2500 ppm dosage, as it solubilizes ∼290 ppm silica after 72 h. Its efficiency is dosage-dependent. DETPA is also an effective silica d...

Initial Stages of Barium Sulfate Formation at Surfaces in the Presence of Inhibitors

The formation of barium sulfate (BaSO4) in the oilfield is known to occur as a precipitation process from the aqueous phase within oil production facilities. This barite deposition causes many problems related to flow assurance. In this paper, the initial stages of barium sulfate deposition on a metallic surface are investigated. The mass rate of deposition of barite on the surface was measured using a quartz crystal microbalance (QCM). The morphology of the deposited BaSO4 was then observed directly with an atomic force microscope (AFM) and the main crystal faces of barite were identified. Both the formation kinetics and the crystallography of the deposited barium sulfate were studied at three supersaturation ratios and in the presence and absence of 2 chemical scale inhibitors, namely, polyphosphino carboxylic acid (PPCA) and diethylene triamine penta acetic acid (DETPMP). In addition, the precipitation of the barite in the bulk phase was also monitored (by turbidity measurements) thus giving a more complete description of the overall bulk/surface barium sulfate kinetics. PPCA proved to be an effective barite inhibitor both at the surface and in the bulk phase in these measurements. DETPMP did not perform so well but there are several reasons why this may be so in such early time experiments and these are discussed in the paper. Thus, such experiments must be interpreted with some caution when we are relating the results to the oilfield scale system. In the industrial application addressed here, the brine system is very specific in that it is at relatively high ionic strength, the divalent cations (Ca2+/Mg2+/Sr2+) play an important role and the supersatuaration ratios of barite are very high. However, barite deposition is currently a very significant problem in the oil and gas industry, and this paper presents findings that will contribute to better ways of managing barite scale in the future.

Efficiency assessment of inhibitors on CaCO3 precipitation kinetics in the bulk and deposition on a stainless steel surface (316 L)

Calcium carbonate (CaCO3) is a common type of scale. Since the beginning of the XXe century, chemical inhibitors, such as PolyphosphinoCarboxylic acid (PPCA), were used to reduce and suppress the scale precipitation, assuming that it would act in the same way on scale deposition on surfaces. Desalination plants and oil industries are currently facing severe restrictions concerning the discharge of oilfield chemicals into the environment. CarboxyMethyl Inulin (CMI), PolyAspartate (PA) and PolyMaleic Acid (PMA) are three inhibitors commonly referred to as “green” products. This paper compares the effect of these inhibitors on the CaCO3 bulk precipitation and deposition on the surface of austenitic stainless steel (316L), at 70°C, under a controlled turbulent flow regime. This study shows that calcium carbonate full inhibition requires higher concentrations for scale deposition than for scale precipitation. Green inhibitors require higher concentrations to reach PPCA inhibition efficiency on both calcium carbonate formation mechanisms.

Assessment of barium sulphate formation and inhibition at surfaces with synchrotron X-ray diffraction (SXRD)

The precipitation of barium sulphate from aqueous supersaturated solutions is a well-known problem in the oil industry often referred to as ‘scaling’. The formation and growth of barite on surfaces during the oil extraction process can result in malfunctions within the oil facilities and serious damage to the equipment. The formation of barium sulphate at surfaces remains an important topic of research with the focus being on understanding the mechanisms of formation and means of control.In situ synchrotron X-ray diffraction (SXRD) was used to investigate the formation of barium sulphate on a stainless steel surface. The effect of Poly-phosphinocarboxylic acid (PPCA) and Diethylenetriamine–penta-methylenephosphonic acid (DETPMP) which are two commercial inhibitors for barium sulphate was examined. The in situ SXRD measurements allowed the identification of the crystal faces of the deposited barite in the absence and presence of the two inhibitors. The preferential effect of the inhibitors on some crystal planes is reported and the practical significance discussed.

Inhibition of Calcium Sulfate and Strontium Sulfate Scale in Waterflood

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. The results showed a large extent of permeability damage caused by calcium and strontium sulfates that deposited on the rock pore surface. At higher temperatures, the rate of CaSO4 and SrSO4 precipitation increases because the solubilities of CaSO4 and SrSO4 scales decrease with increasing temperature. At 90°C temperature, PBSI was the best inhibitor because it reduced more scale deposition compared to the DETPMP and PPCA inhibitors.