Abstract
Bhagyam is a shallow onshore field in the northwestern region of India developed by Cairn Oil & Gas, a vertical of Vedanta Limited in two different phases with over 106 oil-producers with deviations as high as 70° and Dog Leg Severity (DLS) up to 7 deg/30m. Rod driven Progressive Cavity Pumps (PCP) were selected as the primary mode of artificial lift. The produced fluid properties which included high wax content and variable fluid viscosity ranging up to 250 cP were the main drivers in the selection of PCPs. A total of 250 unique installations of PCP systems have been completed in over 100 wells. These systems have accumulated a cumulative run-time of over 150,000 days over a total period of more than 2550 days from first installation, with an average tubing-pump system run-life of 600 days.
A major disadvantage of using a rod driven artificial lift system is metal to metal wear between rod and the tubing during operation. This metal wear in rod and tubing results in string failure, increasing costly well interventions and increased system downtime. This paper will demonstrate through specific case studies how pump operating parameters and well design were optimized over time to reduce well interventions and operating expenditures (OPEX).
A centralized data base with real time data configured with a predictive analytical model and automated performance analyzer have enhanced PCP monitoring and troubleshooting. Predictive modelling has improved preventative maintenance such as preemptive rod change outs which greatly reduced the number of rod failures increasing system uptime. In conjunction with joint industry program, detailed root-cause analysis supported with Dismantle Inspection and Failure Analysis (DIFA) laid the foundation for operational and design improvements in PCP operated wells.
Some of the recent improvements employed in system design for PCP operated wells are:
Installation of through tubing PCP on an insertable anchor/pump sitting nipple
Installation of packer with completion string
Use of peened rods with molded guides
Snap-on and spin thru guided rods
Installation of externally flushed hollow rod string
Replacement of conventional vam top tubing with boronized tubing
Installation of high volume PCPs.
