METHOD OF PREVENTING HYDRATES FORMATION IN WELLS (VERSIONS) Russian patent published in 2002 - IPC

FIELD: oil and gas producing industry. SUBSTANCE: method is designed for prevention of hydrates formation in wells, mainly, in oil wells drilled in permafrost rocks. According to the first version of claimed method, zones of local drop of annulus temperature are preliminarily detected. Prior to supply to local zones inhibitor is heated to form vapor phase. Process of inhibitor heating up to vapor phase is carried out at wellhead, or in detected local zones, or directly under lower boundaries of detected local zones. Inhibitor is continuously supplied by portions in amount ensuring its preset concentration for condensation in annular space with consideration of gas composition, well production rate, temperature and pressure conditions. In preferable versions of method realization, inhibitor is mixed with gas after its conversion into vapor phase at wellhead, for instance, with natural gas coming from annular space, and heated to temperature preventing premature condensation of inhibitor before reaching the detected zones of local temperature drop. Process of inhibitor heating to vapor phase is performed directly in zone of local temperature drop by its supply from wellhead to vessel with heating element located in said zone. Inhibitor is supplied from wellhead simultaneously or successively to a number of vessels with heating elements located consecutively in well depth. According to the second version, zones of local temperature drop in annular space are preliminarily detected, and inhibitor is supplied from wellhead to upper boundary of local temperature drop detected zone. Inhibitor is supplied continuously or by portions in amount ensuring its preset concentration in annular space with consideration of gas composition, well production rate and temperature and pressure conditions. It is good practice to correct amount of inhibitor introduced depending on pressure in annular space and to use inhibitor in the form of methanol or diethylene glycol in both versions. Realization of said method by both versions provides practically for complete exclusion of hydrates formation in annular space of wells. EFFECT: higher efficiency. 5 cl, 4 dwg, 1 ex