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Summary Barium sulfate scale deposition in the near wellbore, perforations, or production tubing has severely affected well productivity in many North Sea Fields. This is due to the co-mingling of the sulfate-rich seawater used for reservoir sweep with formation water containing high concentrations of barium ions. Mitigation of this problem is generally achieved by regular "squeeze" deployment of scale inhibitor chemicals which retard scale precipitate formation and deposition. However, in some instances, the scale inhibitor is poorly retained within the reservoir rock matrix and short squeeze lifetimes are experienced. The net result in these cases is frequent well interventions which impact on both well productivity and field profitability. To solve this problem, a scale squeeze enhancer has been developed which acts to enhance retention and subsequent release of scale inhibitor in the reservoir. The first field deployment of this technology was in BP's Magnus asset. The trial demonstrated a more than doubling of the squeeze lifetime of an adsorption chemical.

New bismaleimides (BMI's) have been synthesized in the Bisphenol A, terphenyl, and tetraphenylketazine series. In three monomers, an additional functionality has been introduced with respect to conventional bismaleimides [viz., allyl, N-maleimido, and ketazine]; a new term, «reactive building block» BMI's, is introduced to describe such monomers. Cure profiles for new monomers have been determined by dynamic mechanical thermal analysis by supporting them on glass braids. Resins have been prepared on a multigram scale and have been studied by thermal gravimetric analysis for evaluation of thermal and thermooxidative stability

Polystyrene and poly(phenylene methylene) of relatively low molar mass (2000–3000) have been converted through nitro and amino derivatives into maleimido-functionalized oligomers. The latter have been characterized spectroscopically and oligomers and cured resins derived therefrom studied by thermal gravimetric analysis. Both polystyrene and poly(phenylene methylene) show greater thermal and thermo-oxidative stability than the corresponding maleimido derivatives. This trend is also observed when comparing poly(phenylene methylene) with the crosslinked resin derived from maleimidopoly(phenylene methylene). The opposite trend is observed for polystyrene and the cured resin derived from maleimidopolystyrene.

Dynamic mechanical thermal analysis (d.m.t.a.) profiles have been recorded for interaction of m-tolualdehyde azine and 3,5-dimethylpyridine N-oxide with the bismaleimide (BMI) derived from 3,3-diaminobenzophenone. Additional chemical events for each system are recognized at temperatures below the conventional BMI curing region. Resins prepared from the BMI/azine and BMIN-oxide systems have lower thermal stability than the neat resin but differences are moderate at low additive concentrations.

Novel aromatic polyimides prepared via the polymerization of monomeric reactants (PMR) approach and incorporating anthraquinone diamines in the main chain have been characterized. Imidization and crosslinking reaction profiles have been delineated by d.m.t.a. and the high-temperature mechanical and thermal properties of the thermoset resins examined. Elevated glass transition temperatures (> 300°C) are apparent in some resins while impairment of mechanical integrity is not evident below 450°C. All resins show good thermal and thermo-oxidative stability.

Polyimide oligomers (prepolymers) and resins of the PMR-15 type have been prepared from 5-norbomene-2,3-dicarboxylic half acid ester (NE), 3,3',4,4'-benzophenone tetracarboxylic diester (BTDE) and a series of diamines incorporating 1,2,3-triazole, quinoxaline, pyrido[2,3-b]pyrazine, pyrido[3,4-b]pyrazine, benzo[g]quinoxaline, pyrazino-[2,3]-d]pyridazine and bis(pyrido[3,4-b]pyrazino)benzene ring systems. Two tetraamines in the bis(pyrazino[2,3-d]pyridazino)benzene ring system were also employed. Selected diamine monomers from the above ring systems provde PMR-15-analogue resins of higher thermal and thermooxidative stability than PMR-15 itself. The physical behaviour during oligomerization and curing of PMR systems has been studied by dynamic mechanical thermal analysis (DMTA). Traces akin to that from PMR-15 are obtained using certain diamine monomers (e.g. triazole and pyrido[3,4-b]pyrazine containing) but a featureless thermogram is observed using tetraamines in the bis(pyrazino[2,3-dj]pyridazino) benzene system.

Investigation of the influence that monomer structure plays in determina tion of the nature of thermoset PMR polyimides has revealed new information regarding the cross linking reaction profile and resultant resin properties. Replacement of BTDE by ODPE as dianhydride shows reduced resin T g values. Synthesis of a new series of alkylene dianilines, with increasing flexibility within the homologous series, evinces lowered cross-linking onset temperatures and T g transitions. Increasing degrees of meta catenation in extended diamines also result in lowered T g values.

Abstract Barium Sulfate scale deposition in the near-well-bore, perforations or production tubing has severely affected well productivity in many North Sea Fields. This is due to the commingling of the sulfate-rich seawater used for reservoir sweep with formation water containing high concentrations of barium ions. Mitigation of this problem is generally achieved by regular 'squeeze' deployment of scale inhibitor chemicals which retard scale precipitate formation and deposition. In the squeeze procedure, scale inhibitor is injected several feet radially into the production well where it is retained by adsorption and/or formation of a sparingly soluble precipitate. The inhibitor slowly leaches into the produced water over a period of time and protects the well from scale deposition. However, in some instances, the scale inhibitor is poorly retained within the reservoir rock matrix and short squeeze lifetimes are experienced. The net result in these cases is frequent well interventions which impact on both well productivity and field profitability. To solve this problem, a scale squeeze enhancer has been developed (jointly by BP Exploration and BP Chemicals) which acts to enhance retention and subsequent release of scale inhibitor in the reservoir. The first field deployment of this technology was in BP's Magnus asset. The trial demonstrated a more than doubling of the squeeze lifetime of an adsorption chemical and has subsequently led to considerable cost savings for the Magnus asset by reducing well intervention frequency and subsequent well downtime. Introduction Magnus Field History. The Magnus oilfield lies approximately 160 km north east of the Shetland Islands in the UK Sector of the North Sea. The field is located in blocks 211/7a and 211/12a, and is producing through the most northerly platform on the UKCS. The Magnus oilfield was discovered by BP in 1974 and first production commenced in August 1983, reaching a peak annual average production rate of 144,301 stb/day in 1994. Reservoir Description. The Magnus field is divided into three producing intervals, the Turonian Reworked Sandstone, which overlays the Magnus Sandstone Member (MSM), which overlays the Lower Kimmeridge Clay Formation. The producing interval initially contained an estimated volume of 1,650 mmstb of oil in place. The MSM lies at a sub-sea depth of approximately 3000m and is currently the main producing formation, having originally held 77% of the initial oil in place. The MSM is the most well defined of the Magnus formations, and can be broken down into several discrete sandstone zones or lobes, separated by shale mudstone units, which act as vertical permeability barriers. The typical MSM permeability is in the range 200–500 mD, with an average porosity of 21% and a maximum net pay of 108 m. Reservoir Management. The Magnus reservoir is currently being drained by 15 producing wells, while 9 further wells, including 3 sub-sea tie-ins, are injecting seawater to support the reservoir pressure. However, off-take from the field to date has exceeded the volume injected, resulting in a significant drop in reservoir pressure from an original value of 6650 psi to a current average of approximately 3000 psi. In addition, a significant pressure gradient exists across the field, with a maximum of 7500 psi observed in certain injectors, compared with 2750 psi measured in several crestal producers. The field is now produced on a voidage replacement basis, however, significant differential pressure exists between lobes as a result of divergent pressure depletion through the MSM. Nature of Scale Problem. An analysis of the ionic composition of the formation waters produced from the various lobes or zones reveals subtle differences in their chemistry; however, in each case the produced water has a salinity almost identical to sea water. In addition, the barium concentration in Magnus formation water is in the range 160–220 mg/l. P. 161^

Isolates of Mucor amphibiorum and Mucor circinelloides from ulcerated platypuses (Ornithorhynchus anatinus) in the north of Tasmania were compared with isolates of M. amphibiorum taken from cane toads (Bufo marinus) in Queensland. Sphaerule-like bodies previously associated with in vivo growth of M. amphibiorum were produced in vitro. Two types of sphaerule-like bodies were observed. Type 1 bodies were found only in +ve mating types. Type 2 were found in both +ve and -ve mating types. Both type 1 and type 2 sphaerule-like bodies were apparent in sections of tissue taken from ulcerated O. anatinus. Type 2 bodies were induced in M. circinelloides, a species not previously associated with the formation of sphaerule-like bodies, either in vivo or in vitro.