Three candidate asphaltene inhibitors have been laboratory tested for their effectiveness on a Canadian crude. One inhibitor, an oil-soluble polymeric dispersant developed by Shell Chemicals, showed superior behaviour compared to the others: flocculation titrations with n-heptane resulted in an optimum concentration of 1300 ppm. PVT calculations, however, indicated that the prevailing conditions downhole can be quite favourable with respect to the amount of effective inhibitor compared to the atmospheric laboratory titrations which appear to be quite severe tests. Therefore, lower initial concentrations were recommended for a field trial. The chemical could be continuously injected through a capillary string, thereby avoiding the lost oil production associated with solvent cleaning operations. It has proved to be very effective at concentrations as low as 66 ppm, resulting in both a technically and an economically successful trial. Introduction Precipitation of asphaltenes in reservoirs, wells and facilities has a severe detrimental impact on the economics of oil production because of a reduction well productivity and/or clogging of the production facilities. The nature and behaviour of asphaltenes in crude oils is complex. Asphaltenes are heterocyclic macromolecules mainly consisting of carbon and hydrogen and minor components such as sulphur, nitrogen, and oxygen. It is generally accepted that resins and maltenes (these structures are comparable to asphaltenes but with a much lower molecular weight) are responsible for keeping the asphaltene particles in dispersion. The asphaltenes are surrounded by the polar head groups of the resins and maltenes while the nonpolar alkyl tails interact with the oil phase. So, crudes with a high ratio of resins to asphaltenes are less subject to asphaltene deposition whereas crudes with large amounts of non-polar saturates compared to aromatics are more prone to exhibit asphaltene precipitation problems. At "normal" reservoir conditions the asphaltenes, resins, maltenes and oil phase are in thermodynamic equilibrium. This equilibrium can be disturbed by a number of factors: decline of the reservoir pressure towards the bubble point, change in temperature or addition of a miscible solvent to the oil as applied in various EOR techniques. Much research has been focused on modelling the deposition behaviour of asphaltenes in reservoir crudes upon changes in pressure, temperature or composition. These models are based on the Flory-Huggins theory for colloidal systems and calculate the chemical potential for large molecules in the various phases. They require solubility parameters as input. In addition, the industry has made a substantial effort to develop pragmatic solutions to the problem of asphaltene deposition in producing wells.

Development of water-based mud systems that approach the performance of oil-based muds is an ongoing effort. Starch-lubricant compositions were developed as environmentally safe, non-toxic, stable dispersions in water-based drilling muds. Starch-lubricant compositions were prepared by jet cooking mixtures of water, starch, and lubricant to produce aqueous starch dispersions containing suspended lubricant droplets 1–10 microns in diameter. These droplets do not separate or coalesce. The dispersions were drum dried and milled to dry, non-oily powders containing 28% lubricant by weight. These dry powders were then tested at 5 lb/barrel in laboratory-prepared lignosulfonate drilling muds. Various commercial olefins, esters and/or polybutenes were evaluated as lubricants. Standard laboratory tests indicated that starch-lubricant compositions lowered both API and HTHP fluid loss values. More importantly, coefficient of friction values were 12–25% of the untreated base mud and were similar to the average values for oil-based muds. Muds formulated with starch-lubricant compositions usually contained only 0.5% lubricant (v/v), yet performed better than a typical field mud control containing 3% lubricant (v/v). These exceptionally good results with one-sixth the amount of a typical lubricant suggest that the size and distribution of lubricant droplets achieved in these systems may enhance lubricant efficiency. Therefore, further investigation of such formulations is warranted, including a field test to evaluate the advantages of this newly-patented technology. Introduction Drilling muds have various functions, including carrying cuttings from the hole, cleaning and cooling the drill bit, reducing friction between the drillpipe and the wellbore or the casing, and maintaining the stability of the wellbore. These mud formulations should also be non-hazardous to personnel and the environment.1–3 Today, most of the world's drilling operations use water-based drilling muds, and only 5 - 10% use oil-based muds. Although oil-based muds have lower coefficient of friction values and better wellbore stabilizing characteristics, the current trend in the oil and gas drilling industry is to increase the use of water-based muds. Some of the factors influencing this trend include changing environmental regulations intended to restrict toxic and non-biodegradable materials, logistical problems in remote locations, gas solubility in oil-based fluids, advances in lubricant additives and borehole stabilizers, and the lower cost of water-based muds. Research is currently aimed at developing environmentally safe, biodegradable, non-toxic, water-based muds that will have better lubricity, improved high-temperature performance, and better hole cleaning properties. Starch-lubricant compositions were prepared by jet cooking mixtures of lubricant, water and starch4–9. Jet cooking is a technology that has been used for decades to prepare starch solutions for industrial applications and involves pumping an aqueous starch slurry through an orifice where it is mixed with steam at high pressure and temperature10. When lubricant is added, the intense turbulence and high temperature within the cooker uniformly disperses the lubricant in the aqueous starch solution as droplets approximately 1–10 microns in diameter. These droplets do not separate and coalesce, even after prolonged standing, and dispersions can also be drum dried and reduced to dry, non-oily powders. Powders can then be redispersed in water at the drilling site to produce stable aqueous dispersions that resemble the original dispersions obtained from the jet-cooker.

Die Waschkraft der Natriumsalze von 2‐Methylalkancarbonsäuren, der primären Alkylsulfate und der linearen Alkylbenzolsulfonate auf Baumwollgewebe wurde in Abhängigkeit vom Molekulargewicht, vom Gehalt an WAS bzw. an Natriumtripolphosphat, von der Wasserhärte, vom Calcium/Magnesium‐Verhältnis und von der Temperatur beurteilt. Dazu wurde auf Basis der Versuchsergebnisse eine Regressionsgleichung abgeleitet, die die Waschkraft zu den sechs Zustandsvariablen in Beziehung setzt. Die wichtigsten Schlußfolgerungen sind folgende: Unter normalen Waschbedingungen sind die Natriumsalze der 2‐Methylalkancarbonsäuren die besten Produkte, die primären Alkylsulfate rangieren an zweiter Stelle. Bei gegebener Wasserhärte ist der Gehalt an Natriumtripolyphosphat die wichtigste Variable; darauf folgen das Molekulargewicht und der WAS‐Gehalt und an dritter Stelle die Temperatur.

kBSTRACT INTRODUCTION Laboratory research on the steam-foam process as The effectiveness of steam injection into a heavy a means of reducing steam mobility in steam-injection oil reservoir can be increased by improving the aerial projects indicates that steam-foam formulations, which and vertical distribution of the steam. llsiscan be are effective in pilot tests at low steam accomplished by reducing the steam mobility; one temperatures, are not necessarily effective at method of doing this is to inject steam with foaming temperatures over 200~. agents' as currently appliad in various US projects.However, long-chain alkylaryl sulphonates exhibit In a steam-soak well the development of a steam an excellent capability for reducing steam mobility at tongue, reaching deep into a reservoir, is beneficial elevated temperature; furthermore, this class of for the activation of oil production mechanisms. surfactants is thermally stable. The performance of However, reservoirs often consist of several permeable steam foam with these surfactants has been studied in sands separated by ehale breaks. If steam is injected core-flow experiments at steam-injection tefrperatures into such a reservoir, steam injection wL1l often be representative of steam operations in the Tia Juana restricted to the top sand. 'lW.ssituation can be field, Venezuela and as a function of the following improved by reducing the steam mobility with foam, parameters: surfactant molecular weight and which will cause the steam-injection pressure to concentration, the presence of an electrolyte, the increase and the steam to be diverted to lower sands. addition of small amounts of a non-condensable gas, and steam quality. me surfactant molecular weight and Most of the experience gained so far with steam concentration appear to be the main parameters for foam in the USA is related to shallcw reservoirs where reducing steam mobility.pressures and temperatures are relatively low. However, in other areas, for example, the Tia Juana The laboratory research was followed by a pilot field in Venezuela, much higher pressures an3 Lest, operated by Flaraven,in the Tia 3aana field, in corresponding temperatures are used. Furthermore, in attempt to improve the injection profile in steam-steam qualities are different, varying from 50 to 60% 3oak wells.in the California fields, and from 80 to 90% in the L%e results obtained so far indicate the feasibility Tia Juana field. >f: . reducing the effective steam permeability, This paper deals with the joint research efforts plugging the most depleted layers, of Shell and Maraven on the mobility-reducing . diverting the injected steam to non-producing sands, capability of foaming agents for the high temperatures . enhancing oil production.prevailing in the Tia JUana field (21 bar, Zls"c). 3ased on the test results and operational conditions, the possibility of optirrdsingsteam-soak operations The laboratory work involved selecting a under Solivar coast conditions has been established. candidate surfactant and evaluating the steam...

r t 1 a ti d wid H . M . M u i j s Arts drm E~oiii~iklijkelShell-Laboratori~r,n, Anisterdatn (Shell Resenrch N . V . ) Der bci Frottiergeweben unter Clem EinfluD eines Waschmittals erzielte Weichhcitsgrad ist sowohl von der Struktur des Gewebes und dem Molekulargewicht als auch von der Harte des Wassers abhangig; dies hangt mit der Adsorption des Waschmittels an die Faset zusammen. D e t h o d s t e Weichhcitsgrad wird erzielt. wenn dem letzten Spiilwasser des Waschvorgangs ein kationaktives oberfladwnaktives Mittel ZUgesetzt wird. Jedoch macht das heutzutage iiblihe Handelsprodukteine quaternare Ammoniumverbindungdas Waschgut ziemlich stark wasserabstoDend. Es wurde nun festgestellt, daB bestimmte Sulfoniumverbindungen dem Waschgut einen sehr weichen Griff erteilen, ohne dab sie erhebliche Wasserabstobung verursachen.