Hydraulic and mechanical integrity of the well : master's thesis

NORSOK D-010 standard definira integritet bušotine kao: ”Primjenu operativnih, tehničkih i organizacijskih rješenja u svrhu smanjenja rizika od nekontroliranog ispuštanja ležišnog fluida tijekom životnog vijeka kanala bušotine“. Primarna barijera (isplaka, cementni kamen, zaštitne cijevi, dubinski sigurnosni ventil) predstavlja prvi stup obrane od nekontroliranog dotoka ležišnog fluida, dok sekundarna barijera (cementni kamen, bušotinska glava, preventerski sustav, erupcijski uređaj) čini vanjsku zaštitu ukoliko elementi primarne barijere ne obave temeljnu zadaću. Sustav upravljanja integritetom bušotina kojeg čine stručno osoblje, oprema i sustavni procesi predstavlja rješenje za definiranje obveza, zahtjeva i odgovornosti kompanija u naftnoj i plinskoj industriji za upravljanje rizicima od gubitka bušotine tijekom životnog vijeka bušotine. Shematski prikaz barijera pruža bolji uvid u stanje barijera i njihove uloge pri djelovanju na nekontrolirani dotok fluida, dok metoda stabla kvarova omogućuje sustavnu procjenu mogućih rizika koji mogu narušiti integritet i kontrolu nad kanalom bušotine. Neadekvatna ugradnja, loša kvaliteta i neispitanost hidrauličkih i mehaničkih elemenata barijera, te manjak znanja i loša komunikacija stručnog osoblja mogu dovesti do katastrofalnih posljedica, kao što je bio gubitak integriteta bušotine na polju Macondo u Meksičkom zaljevu 2010. godine.The NORSOK D-010 standard defines well integrity as: "Application of operational, technical and organizational solutions to reduce the risk of uncontrolled release of formations fluid throughout the life cycle of a well". The primary barrier (mud, cement, casing, downhole safety valve) is the first pillar of defense against uncontrolled inflow of reservoir fluid, while the secondary barrier (cement, wellhead, blowout preventer, “Christmas tree”) provides an external protection if the primary barrier elements do not perform the basic requirements. Well integrity management system, consisting of professional crew, equipment and systematic procedures, presents solution for defining the obligations, requirements and responsibilities of a company in the oil and gas industry to manage the risks of well loss during the life cycle of a well. Well barrier schematic provides a better visualization of barrier conditions and their role in an attempt to protect uncontrolled fluid inflow, while the fault tree method allows a systematic assessment of potential risks that may impair the integrity and control of the wellbore. Inadequate installation, poor quality and untested hydraulic and mechanical barriers, as well as lack of knowledge and poor communication of professional staff can lead to catastrophic events, like demonstrated in the Gulf of Mexico in 2010, with the “Deepwater Horizon” incident