Dual gradient drilling methods and riserless drilling : master’s thesis

Predmet istraživanja ovog diplomskog rada su nekonvencionalne metode bušenja, od kojih su posebno obrađene metode bušenja uz dvojni gradijent tlaka (DGD), odnosno metode bušenja bez rajzer cijevi, metoda transporta krhotina (CTS), bušenje s povratkom isplake bez rajzer cijevi (RMR), metoda povrata isplake kroz E-cijev (EdR), bušenje uz istovremeno ugušivanje bušotine (DKD) i metoda bušenja uz primjenu koncentričnog niza bušaćih šipki (RDM). Princip rada metode bušenja uz primjenu dvojnog gradijenta tlaka opisan je na temelju simulacije. Proporcionalno s povećanjem dubina istraživanja za naftom i plinom povećava se i kompleksnost operacija te problemi koji se mogu javiti prilikom njih. Pregledom literature je ustanovljeno kako su najveći problemi mala razlika između slojnog tlaka i tlaka frakturiranja („bušaći prozor“). Upravo korištenje obrađenih metoda, omogućava kvalitetnije bušenje u takvim zahtjevnim uvjetima. Razmišljanje naftnih kompanija polako se mijenja, u skladu s čime se počinju sve više koristiti nekonvencionalne metode koje postepeno zamjenjuju konvencionalne.Abstract: The subjects of this thesis are unconventional drilling methods, mainly dual gradient drilling methods, particularly riserless drilling methods, cuttings transport system (CTS), riserless mud return (RMR), E-duct return (EdR), dynamic kill drilling (DKD) and reelwell drilling method (RDM). The dual gradient drilling method is described through a simulation in order to explain the main functions. With the increase of the depth of offshore exploration, the complexity of operations and the number of problems that follow also proportionally increases. By reviewing the available literature, it was concluded that the main problem occurring in these conditions are the narrowing of the pore pressure and fracture pressure margins, otherwise known as the drilling window. Thus, by using the methods covered in this thesis, it becomes possible to drill more efficiently in such demanding conditions. The consensus of the drilling industry is slowly shifting and methods once known as conventional are slowly being replaced by unconventional ones