Abstract

The increasing water production in mature fields has a significant impact on production economics. A structured approach is required to tackle this challenge. Water shut-off (WSO) operations in open-hole horizontal wells do not carry a high success rate, however, careful candidate recognition and treatment can improve the chance of success. Ratawi is an Oolitic Limestone reservoir in Wafra oilfield, Partitioned Zone (PZ) between Saudi Arabia and Kuwait. The reservoir has been undergoing water-flooding for pressure maintenance since 1998. Majority of the wells are completed as open-hole horizontal producers on artificial lift.

The paper describes WSO performed in the biggest water producing well in Ratawi field with 94% water cut. Being located in the crestal area, where the preservation of reservoir energy has been a focus of the reservoir management strategy, made it a prime target for WSO which could lead to water flood optimization and improved sweep efficiency. The water shut-off treatment was designed with two-fold objective; primarily, to plug-off the fractures and the near wellbore area suspected to produce water and secondly, to isolate the open-hole to prevent the damage to the oil bearing zones.

The challenging conditions for WSO required a synergistic approach by combining the latest technologies to achieve the desired objective. Real-time downhole measurements from the Fiber Optic Assisted Coiled Tubing (FOACT) were combined with the Open-Hole Inflatable Bridge Plug (OHIBP) to improve operational reliability while reducing risks of failure. The real time measurements assisted in reliable single-run OHIBP inflation under sub-hydrostatic conditions and also played a vital role in fine tuning the gel concentration in real time based on the formation response.

Due to this holistic approach, 4000BWPD was eliminated and 30% oil gain was observed without any subsequent acidizing. Moreover, the additional cost of a replacement well and abandoning the existing well was saved. The success of this treatment opens the opportunity to apply the same technique to other potential candidates across the globe.

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