Overcoming Artificial Lift Failures in Polymer Flooding Oil Field in the South of Oman

Abstract

Abstract Polymer flood as a mean of enhanced oil recovery was applied in a large sandstone heavy viscous (22API & 90cP) oil field located on the South of the Sultanate of Oman. The polymer flooding was commenced in 2010 with phase I covering 27 patterns, by means of inverted 9-spot pattern. In 2015, Phase I was followed by Phase II with additional 19 patterns. Full field polymer flooding is planned in the coming years. Over 250 oil producers are benefiting from changing the recovery mechanism water flooding system to the increased viscosity flood system (polymer). Significant oil gain was achieved by improving the recovery factor. Around 92% of the total wells in the field are completed with the two main artificial lift systems, beam pumps BP and Progressive Cavity Pump PCP. After circa three years of introducing the polymer flooding in the field, new trend of well failure rate was observed in which the artificial lift failure rate was increased by around 40% by end of 2014. This has massively increased work-over job frequencies and cost, and has significantly increased the crude oil production deferment. New type of failure mode was seen in the sucker rod and tubing of the BP & PCP. Severe eccentric wear of sucker rods and tubing in many vertical wells with pumping unit have accrued in which the coupling was worn out and broken from one side i.e. most of phase I & phase II wells experienced premature or frequent failure. By end of May-2015, 83% of failure were associated to pump failures and it is more related to well conditions. Material analysis of the damaged sucker rod & plungers were conducted & the failure mechanism of both parts of the beam pump was investigated. Around 73% of the pump failures were found to be due to solids handling (sand, scale solids) & corrosion issues or combination of both, erosion & corrosion mode of failure. On the other hand, around 60% of rod failures of the polymer flooded wells were due to wear. Set of trials and initiatives were conducted to improve the sucker rod run life and reduce the failure rate. For example, centralized molded sucker rod, continuous rod (pro-rod), GRE lined tubing and long stroke pump (roterflux). Some good success was achieved in arresting the failure rate and improving sucker rod run-life. Material analysis studies & trials were also conducted to improve the barrel life. Evaluation of the various trails are currently ongoing and still at early stage to draw clear conclusions. This paper will discuss the material analysis studies and the main practical trials that were conducted to reduce the pump and rod failures, and therefore improve well run-life in the field.