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Jaffar, Ali Hussain (Kuwait Oil Company) | Mohammed, Jassem Ali (Kuwait Oil Company) | Khaja, Mohammed (Kuwait Oil Company) | Haddad, Hassan (Kuwait Oil Company) | Raturi, Sushil (Kuwait Oil Company) | Albohamad, Dalal (Baker Hughes) | Abdel Lateef, Emad (Baker Hughes) | Aldakheel, Rashed (Baker Hughes)
Cementing the 7″ liner in UG field has always posed a great challenge due to the poor cement bonding across the target production zone, Minagesh Oolite. This is due to the high water influx, from the proximity of the aquifier drives to the production zone, hence leading to contamination of the cement slurry during the cementation. This has resulted in the loss of zonal isolation in addition to the unwanted water production. Water cut production has been observed to rise from 30% upto 70% and 90% within the course of less than 10 years. This has burdened a major Middle East operator with increased cost associated with remedial cementing jobs & disposal of water. Furthermore, conventional water shut off techniques, including cement plug back techniques, were proven to be largely ineffectual, hence an efficient control method was sought out as an alternative.
This paper discusses the implementation of an optimized, fit for purpose cement slurry, with enhanced mechanical and self-repairing properties along with the operational optimization in West Kuwait UG field which has improved the overall cement quality around the liner along with the reduction of water content (WC%) with production throughout a six month observation period.
An optimized, fit-for-purpose cement slurry system, with expansive and enhanced mechanical properties was developed and tested to simulate the conditions downhole during and after the 7″ liner cementation. Self-repairing, also known as self-sealing, and expansion properties in the presence of water and hydrocarbons were also tested by inducing fractures in the cement and observing the expansion and swelling capability in the presence of up to 90% water and only 10% hydrocarbon.
The self-sealing slurry was implemented in a step by step in a planned manner in UG field, with preset KPI's so as to evaluate the effect of slurry on water intrusion. Furthermore, operational execution and optimization was also considered to ensure a flawless cementing job execution.
Implementation of the first 3 self-sealing cementations of 7″ liner in UG field, showed great improvement in the cement bond log after 48hrs of cement placement. Further, the water cut in one case was reduced from 52% after initial testing to 24% and 22%, in subsequent 3 month and 6 month evaluation, respectively. This technology has also been used in other fields across Kuwait where water intrusion is apparent and different downhole conditions were observed. There is a large scope to use this technology as high water cut and poor cementation is a very common problem across different fields.
KOC has been producing oil using dual completions from different pressure regime zones from the same well and South East Kuwait field has many such dual completions wells which are currently being converted from natural flow completion to artificial lift completions. In one of such dual completion naturally producing well, first time in world an artificial lift system - Anchor Pump was installed in Short String (SS) through rigless intervention. Thus project well had un conventional dual completion in the field first of its kind i.e. Sucker Rod Pump (SRP) installed in short string and natural producer through Long String(LS). The well produced for some time through both strings and an intervention by workover rig was required due to high water cut and stuck anchor pump in short string. The paper describes the challenges and initiatives and learnings for safe execution of unconventional dual completion well workover.
Due to combination of natural flow and SRP artificial lift completion, the X-mas tree configuration and associated surface equipment of such well was had several constraints and HSE issues for mobilization of rig and dual production zones with varying pressure regimes have challenges of initial well killing due to plugged short string by stuck anchor pump. The risks were identified during planning stage and risk reduction measures were jointly agreed with Field Development. Various options were explored to minimize risks to ALARP level and subsequently addressed in Work Over Program. The surface equipment constraints were eliminated through rigless works and X-tree configuration were modified to suit deployment of a workover rig. Well process safety principles were applied to accomplish initial well killing in both production zones so as to safely pull out existing dual string completion without any well control issues. An initiative to use sucker rod back off tool, first time and safe back off operation was performed successfully from very close to stuck point.
The existing completion strings were pulled out and further well cleanout and workover program was well cleanout Finally, well was completed with new ESP completion string and successfully production tested. The most important factor in success was proactive planning keeping in view of Process Safety for well control issues and effective communication among the concerned parties.
The initiatives adopted in execution of such a challenging well intervention resulted enhancement in safety to rig crew and Rig operational safety standards in addition to contribution towards cost reduction. Lessons learnt has potential of rig time saving specially during workover of large number of heavy oil wells where stuck sucker rod conditions are very common due to sand invasion in tubing during production.