Основы нефтегазового дела

Lecture 5 • special technical casing for accident elimination and having no connection w i t h previous casing. 4. Production casing. For casing and isolation o f production horizon from others horizons. Through this casing, o i l and gas are getting out from the w e l l . The w e l l design is called the single casing, i f besides conductor and casing, production casing is just installed i n w e l l . I f besides conductor and casing, i n w e l l i t is installed technical casing and production casing, such design is called a double casing (one technical casing) and three casing (two technical casings). The w e l l design is selected taking into consideration geological peculiarities o f field (occurrence depth o f caving-in zones, losses, water inflows, production horizons depth); type o f production fluid ( o i l or gas); methods o f production and d r i l l i n g ; equipment and technology drilling issues. Due to the development o f drilling technology, o i l or gas w e l l designs are underwent considerable changes o f simplification and facility i n the recent times. Simplification means reducing o f clearance between w e l l sides and casings. I t provides reducing o f drilled rock volume and reducing o f cement volume for cementing the w e l l . Facility means the diameter decrease for production casing and consequently diameters o f other casings; refuse to use m i n o r strings (casing, technical casing); depths decrease o f casing installation. A s a result, less volume o f metal used for one w e l l . A n introduction o f rotary method has played a great role i n simplification and facility. I f during percussive method, i t was installed a lot o f concentric casing (sometimes 10-12), i n case o f using rotary method, i t is used only t w o or four casings. This is possible because, impact method is characterized b y absence o f rock cuttings return w i t h drilling m u d , so casings were installed eve...