THE DEVELOPMENT OF A HIGH-PRESSURE DIRECTIONAL DRILLING SYS-TEM FOR GAS WELLS

DIRECTIONAL AND EXTENDED-REACH DRILLING IN GAS FIELDS IS OFTEN EMPLOYED FOR MORE EFFECTIVE GAS DRAINAGE OR, IN CASES WHERE IT IS NECESSARY TO CROSS THE NATURAL FRACTURE NETWORK,TO MAXIMIZE GAS RECOVERY. AS THE DRILLING DIRECTION APPROACHES THE HORIZONTAL, THE RATE OF PENETRATION DIMINISHES AND THE HORIZONTAL REACH DECREASES, SINCE IT BECOMES DIFFICULT TO APPLY SIGNIFICANT WEIGHT ON THE BIT. A SYSTEM THAT COMBINES ULTRAHIGH PRESSURE JETS (30,000 PSI) WITH MECHANICAL BITS HAS BEEN DEMONSTRATED TO BE CAPABLE OF DRILLING EFFECTIVELY AT VERY LOW WEIGHT-ON-BIT LEVELS. THISSYSTEM USES THE ULTRAHIGH PRESSURE (UHP) FLUID JETS TO SLOT THE ROCK BEFORE THE MECHANICAL CUTTERS ACT ON IT. AS A RESULT, THE DRILLED ROCK FAILS IN THE SHEAR MODE INSTEAD OF THE COMPRESSIVE MODE. THIS SUBSTANTIALLY REDUCES THE LOAD REQUIRED ON THE MECHANICAL CUTTERS TO DRILL THE ROCK EFFECTIVELY. IN THIS PROJECT, THE UHP TECHNOLOGY WILL BE EXTENDED TO DIRECTIONAL DRILLING. IN PHASE I, A DOWNHOLE MOTOR ASSEMBLY WILL BE DESIGNED WITH TWO PARALLEL STREAMS OF MUD, ONE AT 3,000 PSI AND ONE AT 30,000 PSI. IN ADDITION, A HIGH PRESSURE SWIVEL THAT CAN OPERATE IN A DEEP HOLE ENVIRONMENT WILL BE DESIGNED AND TESTED. THE SWIVEL IS KEY TO THE SUCCESSFUL TRANSPORT OF HIGH PRESSURE FLUID THROUGH A DOWNHOLE MOTOR. BY USE OF THE RESULTING DESIGN CONFIGURATIONS, THE TECHNICAL AND ECONOMIC FEASIBILITY OF COMBINING UHP JETS WITH DOWNHOLE MOTORS FOR DIRECTIONAL DRILLING WILL BE EVALUATED.