The collapse profiles of foams formed from model aqueous and non-aqueous foaming solutions have been recorded using a novel device, the Optical Transmission Foam Meter. An equation comprising two exponential terms has been used to describe the profiles and an attempt has been made to relate the equation parameters to some of the physical properties of the gas and liquid phases.

Summary Early in the program of commissioning the Ninianstabilization trains at Sullom Voe terminal, problems of severefoaming in the first- and second-stage separators occurred. This resulted in massive carry-over of crude into the gaslines. Injection of a conventional anti-foam compound intothe crude alleviated the problem somewhat. At highergas/oil ratios (GOR's), however, conventional anti-foamagents did not control the foaming, adequately. BP Research Centre at Sunbury investigated the foaming characteristics of the crude and developed, with others, a novel foam inhibitor that effectively prevented foamgeneration in the separators. Also, gamma ray monitoring equipment with alarmsand emergency trips was installed on the separators toprotect the downstream gas-compression trains. protect the downstream gas-compression trains. Brent crude had similar, but less severe, foamingcharacteristics. These problems were solved in the same wayas those with the Ninian crude. Introduction The Sullom Voe terminal in Shetland processes andexports oil and gas from offshore fields in the EastShetland basin, about 100 miles 1161 km) northeast of theisland. The fields are divided into two groups-the Ninian Pipeline Group and the Brent Pipeline Group. Unstabilized crude from each group flows through a 36-in.191 -cm] -diameter pipeline to the terminal. The Ninian pipeline crude comes from two fields, whilethe Brent pipeline crude is from five fields. Theproperties of the crudes from each field are different, properties of the crudes from each field are different, particularly the foaming characteristics. particularly the foaming characteristics. Parallel stabilization trains-two for the Ninian crudeand three for the Brent crude-are located at theterminal. The two crudes have different gas and watercontents and different pressures. Their processing facilitiesand operating conditions are similar but not identical. One Ninian stabilization train was commissioned toprove the plant and to provide gas for power and steam prove the plant and to provide gas for power and steam generation. Very early in the commissioning operation, however, severe foaming occurred in the second-stage(low-pressure [LP]) gas/oil separator, which operated at 0.7 bar gauge [10 lbf/sq in.], when the temperature ofthe initial dead-crude feed was raised to 914 deg.F[490 deg.C]. As a result, large quantities of crudewere carried into the flare relief system. BP Sunbury Research Centre confirmed the severefoaming tendency and recommended a suitable anti-foamagent. Adjusting the operating conditions had little effecton the foam level, but injecting the anti-foam agent andinstalling adequate foam detection and trip systemsbrought it under control. At a later stage in the commissioning process, a verystable foam persisted in the first-stage (high-pressure[HP]) gas/oil separator, which operated at a pressure of1.7 bar gauge [24.7 lbf/sq in.], despite the injection ofconventional anti-foam agent. Further laboratory and planttrials resulted in the development of an improvedantifoam agent that destabilized this foam. As gas rates wereincreased to facilitate the commissioning of downstreamequipment, a degree of unpredictability in separatorperformance became evident owing to the varying quality of performance became evident owing to the varying quality of crude. Adequate techniques to control foam level finallywere developed. They called for appropriate rates ofantifoam addition supported by trip systems. This techniqueprevented significant carry-over of crude into downstream prevented significant carry-over of crude into downstream compressor suction drums. Later, when the Brent stabilization trains werecommissioned, a similar. less severe foaming tendency wasobserved. The phased commissioning program allowedinstallation and assessment of the performance of parallelplates (Dixon plates) in the separators as a method of plates (Dixon plates) in the separators as a method of breaking down foam. Description of the Crude Stabilization Processes Crude from the Ninian and Brent pipelines enters theprocess plant where it is dehydrated and stabilized. The process plant where it is dehydrated and stabilized. The Ninian and Brent pipelines operate at pressures of 26 and 9bar gauge 1377 and 130 lbf/sq in. 1, respectively. The crudestreams are processed separately in that each pipeline feedsa number of parallel dehydration/stabilization trains-two for the Ninian and three for the Brent. Each train isdesigned to produce 330,000 B/D 152 466 m 3 /d] of stabilized crude. One Ninian and two Brent trains are currently operating, and the remaining Brent and Ninian trains willbe commissioned shortly. Figs. 1 and 2 are simplified block diagrams of theNinian and the Brent dehydration/stabilization processes. Ninian Stabilization. Cold Ninian unstabilized crude at26 bar gauge [377 lbf/sq in.) is heated in three stages: first. by exchange of heat with hot stabilized crude;second, with steam condensate; and third, with medium-pressure steam. pressure steam.JPT P. 2211

Abstract The foaming characteristics of a number of crude oils from a variety of sources were determined by Bikerman's pneumatic method. Extraction of these crudes with both alkali and acid indicated that the crude oil components responsible for the foam stability were removed by the alkali extraction. Further examination of the alkali extract revealed that after neutralization it was the chloroform-soluble part of this extract (0.02% wt% of the whole crude) that was responsible for the foaming properties of the crudes investigated. This latter point was confirmed by demonstrating that the surface rheological properties of one of the extracted crudes could be restored by adding back the chloroform-soluble portion of the neutralized alkali extract. Analysis of this extract indicated that the foam-stabilizing materials were short-chain carboxylic acids and phenols of molecular weight ≤400. In principle, such analytical information could be used to identify crude oils likely to present severe foaming problems in the field. Such information could enable the process engineer to take appropriate corrective measures early in the life of a new field, thus avoiding the need for high capital expenditure at a later stage.

The dilatational relaxation spectra of a number of crude oil/air systems have been determined using both the first-order approximations of Ferry et al., and an exact method first described by Wiff. The inferred spectra have been correlated with measured foamability indices, and it has been shown that a decrease in foamability index correlates with a shift in the spectral maximum to longer relaxation times. A contrast is also drawn between the behaviour of defoamers and pro-foamers. The exact method of spectra determination gives rise to line spectra positioned at relaxation times corresponding to the peaks of the first-order spectra. The use of Cole—Cole plots to justify these single line spectra is outlined.

The natural buoyancy of gas bubbles has hampered conventional electrokinetic methods of evaluating charge at the gas-liquid interface.

Crude oil foams can pose major problems for operators of gas/oil separation plants, causing loss of crude in the separated gas stream and consequent loss of revenue and possible damage to downstream compressors. Thus, an understanding of the factors controlling crude oil foam stability is highly desirable as it should lead to better methods of foam prediction and control. With this end in mind, those crude oil components responsible for foam stabilization have been identified. This work outlines the findings to date and attempts to demonstrate that a similar suite of compounds is responsible for the stabilization of a wide range of crude oil foams. 15 references.

The reliable assessment of non-aqueous foam stability is highly desirable in a number of industries which handle non-aqueous fluids. This statement is particularly true for the oil industry where the occurrence of such foams in crude oil/gas separation units and distillation processes can result in a loss of process efficiency, leading to severe financial penalties. Consequently, the development of an understanding of what factors most affect crude oil foam ability along with the development of a reliable means of assessing such foamability would be of great use to the design engineer. Such understanding and techniques would enable potential processing problems to be anticipated and allowed for at an early stage in process design. This paper outlines how work at BP Research on crude oil foams has been directed towards such a goal and discusses the various physicochemical factors studied.

Aqueous dispersions of homoionic sodium montmorillonite have been studied under compressive and decompressive conditions in order to determine the internal pressure of the system as a function of the clay and electrolyte concentrations. Complementary measurements were also made of the electrokinetic properties of the montmorillonite particles. Compression of a sodium montmorillonite dispersion from ca. 2 % to ca. 65 % w/w gave a continuous curve of pressure against distance of plate separation up to pressures greater than 100 atmospheres. On subsequent decompression, however, a different curve was obtained and a hysteresis effect was found to occur in the pressure against distance curves. It is considered that the initial curve represents the behaviour of a disordered clay system, i.e., the initial gel, whereas the decompression curve represents the behaviour of a system in which the plates have become ordered into a parallel array. The elastic modulus of the latter system was determined. The results strongly suggest that the gel properties of montmorillonite dispersions are the consequence of long range electrostatic interactions.