Scale Inhibitor Selection for Continuous and Downhole Squeeze Application in HP/HT Conditions

Tomson²,

et al. 2013

All Days

Polymeric scale inhibitors are widely used in the oil and gas field because of their better thermal stability and improved environmental compatibility. However, the squeeze performance of such inhibitors is typically poorer than that of the phosphonates type scale inhibitors in conventional squeeze treatment. In this research, a new method of delivering chemicals to formation has been developed. Polymeric scale inhibitor nanoparticles were developed for scale control. Boehmite (ɤ-AlO(OH)) nanoparticles (NPs) with particle size from 3 to 10 nm were used to cross-link sulphonated polycarboxylic acid (SPCA). Cross-linked polymeric scale inhibitors were synthesized and developed to increase their retention in formations by converting free flowing water-soluble scale inhibitors into a viscous gel. The viscosity of NPs-polymer gel systems can be manipulated by changing reaction conditions such as NP and polymer concentrations, pH, temperature and ionic strength. Polymer adsorbs to the NP surface via an ion exchange mechanism with hydroxyl group on boehmite. The adsorption and desorption behavior of scale inhibitors onto both nanoparticles and core materials are investigated at different pH and temperature values.

Section: Introductionmentioning

confidence: 99%

Boehmite Based Sulphonated Polymer Nanoparticles with ImprovedSqueeze Performance for Deepwater Scale Control

Tomson²,

et al. 2013

All Days

SPE International Symposium on Oilfield Chemistry

“…That said, some general conclusions with respect to chemical retention in both carbonate and sandstone formations can be drawn from previous literature examples, which illustrate that some chemicals types, such as certain sulphonated polymers and modified "calcium tolerant" phosphonates, have relatively poor retention on the reservoir substrates leading to rapid release when compared with other chemicals. 1,3,8 Performance/Chemical Selection: The spent acid contains very high calcium (and magnesium) concentration typically > 50,000mg/l at mildly acidic pH's (~pH 4). While much of the spent acid in a field treatment is immediately produced back upon clean-up, a portion of it may remain in the reservoir matrix for extended time periods at full reservoir temperature (~210-225 o F).…”

Section: Introductionmentioning

confidence: 99%

“…Many scale inhibitor species, particularly conventional phosphonates and polyacrylate based polymers, suffer chemical incompatibility in high calcium formations. 9 Thermal Stability: The spent acid, although "neutralized", is expected to remain mildly acidic at a pH of ~4. The selected scale inhibitors must therefore remain thermally stable under extended periods of time at full reservoir temperature in the moderately acidic "spent acid" brine.…”

Section: Introductionmentioning

confidence: 99%

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Inorganic Scaling and Chemical Inhibition Challenges Associated with Production of Reservoir Equilibrated Spent Acid Stimulation Fluids

Morrow

Farooqui

Morshidi

et al. 2013

Hydrochloric acid (HCl) is commonly used to remove wellbore damage and to enhance near-wellbore formation permeability in carbonate formations. Although in most cases the spent acid is recovered rapidly during well flow back after the treatment, in heterogeneous reservoirs some of the spent acid can remain trapped for long periods becoming fully saturated with CaCO 3 under downhole conditions. These reservoir-saturated spent acids then lead to scaling when eventually unloaded into the production system. This paper describes a modelling and laboratory study to replicate the system, to allow selection of inhibitors which are effective against carbonate scales in spent acid solutions containing extremely high levels of Ca 2+ /Mg 2+ , and also remain stable at elevated temperatures in the spent acids. The work also examined chemical retention and release via coreflood testing followed by field application modelling to select effective scale inhibitors (SI) which possess poor retention properties on the carbonate substrate thereby remaining present in the "spent acid". One significant challenge associated with this study was the ability to reproduce the mildly oversaturated field scaling environment in the laboratory. When using these fully saturated (with respect to CaCO 3 ) partially acidic brines, very small changes in the brine chemistry or preparation procedures had a significant impact on scaling. A detailed evaluation of brine preparation, stabilisation and buffering was therefore required prior to evaluating generic scale inhibitors for performance under these extreme conditions leading to selection of appropriate species. The second stage of the work then involved core test procedures to determine those chemicals that offered minimal retention properties on the reservoir along with performance. This paper will present the field scaling challenges observed due to unloading of trapped spent acids; describe challenges faced within the laboratory in reproducing these conditions and present results from generic chemical types which are effective at preventing scale under these extreme conditions. From the shortlisted products further results are presented demonstrating those which offer poor retention, which is generally the opposite of what is required for conventional scale inhibitor squeeze treatments, allowing selection for upcoming field trials in the selected field system.

“…But with increased concerns toward environment, phosphonates are prohibited in North Sea. Moreover, they are perceived to be unstable under high temperature condition compared to polymeric scale inhibitors, which typically have better thermal stability Fan, et al 2011;Wang, et al 2009;Graham, et al 1998). Sulphonated polymers such as sulphonated polycarboxylic acids have been developed to meet the increasingly strict bioaccumulation, biodegradation and ecotoxicity regulations (Dickinson, et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Sorption Study of AlOOH Nanoparticle Cross-Linked Polymeric Scale Inhibitors and their Squeeze Performance in Porous Media

SPE International Symposium on Oilfield Chemistry

Kan

Wang

et al. 2013

Polymeric scale inhibitors are widely utilized 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 cross-linked polymeric scale inhibitors were developed for scale control. Nearly monodispersed boehmite (ɤ-AlO(OH)) nanoparticles (NPs) with average size of 2.8 nm were synthesized and used to cross-link sulphonated polycarboxylic acid (SPCA). Cross-linked AlOOH-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. Sorption study of SPCA onto AlOOH NPs under different pHs with and without assistance of Ca 2+ was discussed. In addition, sorption study of various types of scale inhibitors (SPCA, PPCA and DTPMP) onto AlOOH NPs was also performed. Squeeze simulation of neat 3% SPCA, AlOOH(3%)-SPCA(3%) NPs and AlOOH(3%)-SPCA(3%)-Ca NPs were investigated. The results showed that the addition of Ca 2+ ions improve the squeeze performance of SPCA and the normalized squeeze life of such material (8,952 bbl/Kg) was improved more than 60 times compared to that of SPCA alone (152 bbl/Kg).