LIQUIFIED NATURAL GAS (LNG) CARRIERS

Moderni brodovi za prijevoz ukapljenog prirodnog plina su brodovi s dvostrukim dnom čija se klasifikacija vrši prema tipu spremnika. Spremnici su posebno projektirani budući da se u njima skladišti prirodni plin ohlađen na -161 °C, što je temperatura vrelišta metana. Bitna karakteristika ukapljenog prirodnog plina je visoka zapaljivost, o čemu treba voditi računa pri projektiranju i rukovanju brodom. Razvoj brodova za ukapljeni prirodni plin započeo je sredinom dvadesetog stoljeća. Veličina skladišnog prostora tih brodova stupnjevito je rasla do današnje maksimalne veličine od oko 260000 m3. Svjetska flota brodova za ukapljeni prirodni plin danas broji više od 300 plovila.Modern liquefied natural gas carriers are double-bottom ships classified according to the type of LNG tank. The tanks are specially designed to store natural gas cooled to -161°C, the boiling point of methane. Since LNG is highly flammable, special care must be taken when designing and operating the ship. The development of LNG carriers has begun in the middle of the twentieth century. LNG carrier storage space has gradually grown to the current maximum of 260000 m3. There are more than 300 LNG carriers currently in operation

REVIEW OF NATURAL GAS LIQUEFACTION PROCESSES

Prirodni plin se od izvora do potrošača najčešće transportira visokotlačnim plinovodima. Kada je udaljenost između mjesta proizvodnje i potrošnje veća od 4000 km, a i zbog diversifikacije dobavnih pravaca prirodnog plina, sve se više primjenjuje ukapljivanje prirodnog plina i njegov transport brodovima. Konačan izbor procesa za ukapljivanje prirodnog plina ovisiti će o varijablama projekta, stupnju razvoja novih ili poboljšanja postojećih procesa i raspoloživosti potrebne opreme. U radu su prikazani procesi koji se danas primjenjuju za ukapljivanje prirodnog plina i njihova zastupljenost u praksi.High pressure pipelines are the most common way of natural gas transport from a gas field to a processing plant and further to consumers. In case when the distance between natural gas production and consumption regions is more than 4000 kilometers, and due to necessity of natural gas supply diversification, gas liquefaction and its transport by ships is being applied. The final choice of liquefaction process depends on the project variables, the development level of new or upgrading of already existing processes and available equipment. Current natural gas liquefaction processes and their usage in practice are shown in this paper

ISPLAKE NA BAZI FORMIJATA: SASTAV I PRIMJENA

Formate-based fluids has been successfully used in over hunders HPHT well operations since they introduced in field practice. They have many advantages when compared with conventional HPHT drilling and completion fluids such as: minimal formation damage, maintenance of additve properties at high temperatures, reduced hydraulic flow resistance, low potential for differential sticking, naturally lubricating, very low corrosion rates, biodegradable and pose little risk to the environment etc. Formate-based fluids can be applied during deep slim hole drilling, shale drilling, reservoir drilling, salt and gas hydrate formations drilling. The laboratory research was carried out to evaluate the rheological behavior of formate-based fluids as a function of temperature. Formate-based fluids were formulated using potassium formate brine, xanthan polymer, PAC, starch and calcium carbonate. Experimental results show that potassium formate improves the thermal stability of polymers.Isplake na bazi formijata uspiješno se primjenjuju tijekom različitim radova u bušotinama s visokim tlakom i temperaturom. One imaju nekoliko prednosti u odnosu na standardne isplake koje se koriste tijekom bušenja i opremanja bušotina s visokim tlakom i temperaturom, kao npr.: minimalno oštećenje formacije, očuvanje svojstava aditiva kod visokih temperatura, smanjenje trenja, smanjenje opasnosti od diferencijalnog prihvata, poboljšana mazivost, smanjena korozivnost, biorazgradivost i neznatan utjecaj na okoliš. Isplake na bazi formijata našle su svoju primjenu tijekom izrade dubokih bušotina malog promjera, bušenja kroz naslage šejla, bušenje kroz ležišta ugljikovodika, te tijekom izrade kanala bušotine kroz naslage soli i plinskih hidrata. Provedena su laboratorijska ispitivanja kojima je utvrđena ovisnost promjene reoloških svojstva isplaka na bazi formijata u ovisnosti o temperaturi. Isplake na bazi formijata sastojale su se od kalij formijata, xanthan polimera, polianionske celuloze, škroba i kalcijevog karbonata. Ispitivanja su pokazala da kalij formijat poboljšava temperaturnu stabilnost polimera

FORMATE-BASED FLUIDS: FORMULATION AND APPLICATION

Formate-based fluids has been successfully used in over hunders HPHT well operations since they introduced in field practice. They have many advantages when compared with conventional HPHT drilling and completion fluids such as: minimal formation damage, maintenance of additve properties at high temperatures, reduced hydraulic flow resistance, low potential for differential sticking, naturally lubricating, very low corrosion rates, biodegradable and pose little risk to the environment etc. Formate-based fluids can be applied during deep slim hole drilling, shale drilling, reservoir drilling, salt and gas hydrate formations drilling. The laboratory research was carried out to evaluate the rheological behavior of formate-based fluids as a function of temperature. Formate-based fluids were formulated using potassium formate brine, xanthan polymer, PAC, starch and calcium carbonate. Experimental results show that potassium formate improves the thermal stability of polymers