Abstract
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.
