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The Wafra Ratawi, a Lower Cretaceous Oolitic reservoir, located in Kuwait, has been on production since 1956. Production remained flat from about 40 producers until 1990. The field was shut-in in 1990 during the Gulf War. An aggressive drilling program was initiated after 1992 when the field was brought back on-line, followed by a 26-injector peripheral waterflood in July 1998. Production peaked in 2Q 2002. After approximately two years, production dropped in 4Q 2003 with declines approaching 25% AED. The Ratawi Asset Management Team (AMT) investigated the causes of the decline and observed the following:○Reservoir pressure decline near the crestal and the southern regions of the field○Voidage Replacement Ratio (VRR) < 1.0○Water breakthrough especially in the first ring of wells inside the peripheral injection loop○Poor conformance due to high permeability streaks resulting in water breakthrough in wells inside the first ring of producers The Ratawi AMT concluded that a significant portion of the injected water is being cycled out by the first ring of producers that had experienced breakthrough, resulting in poor Voidage Replacement Ratio (VRR), and the consequent depletion in the center of the reservoir. A 20MM$ project was initiated for the enhancement of the existing peripheral waterflood. The project entailed the drilling 4 new horizontal injectors near the crestal region and converting 1 vertical producer to a horizontal water injector near the southern region---the areas of maximum pressure depletion. The injection target was deep, just above a vertically sealing barrier in the reservoir. Intent of the "deep" injection was to implement a gravity stable, bottom water drive to supplement the aquifer in this relatively heavy oil reservoir. To augment the existing waterflood, the Pressure Maintenance Plant (PMP) needed to be de-bottlenecked to capacity of 250 MBWIPD from the nominal 190 MBWIPD. An interesting aspect of this project was the relatively novel dumpflood. De-bottlenecking the PMP would be completed almost a year after the first new injector had been drilled. To accelerate water injection, and to circumvent long lead times associated with injection lines and plant de-bottlenecking, dumpflooding was identified as an option. A dumpflooding source was identified, assessed, and the dumpflood was implemented successfully. In the dumpflood, water from the overlying Zubair aquifer was used to "dump" a total of approximately 60 MBWIPD into the Ratawi. This is a "first" in the Partitioned Neutral Zone, Kuwait. Peripheral injection projects are hard-pressed to maintain reservoir pressure in the center of large reservoirs. Along with the dumpflood, the novelty of this project lies in the use of supplemental horizontal injection to simulate a bottom-water drive in the central portions, which augments the peripheral injection. This paper discusses the genesis of this project through the inception, execution and operation/evaluation of the dumpflood and powered injection phases. Introduction The Wafra field, discovered by Aminoil and Pacific Western (later Getty Oil) in 1954 is located in the Partitioned Neutral Zone - an area between the Kingdom of Saudi Arabia and Kuwait. The mineral rights in this region are shared equally between the two countries. The field is now operated by Saudi Arabian Texaco (SAT), a 100% owned subsidiary of Chevron, and Kuwait Gulf Oil Company (KGOC). SAT operates the field on behalf of the Kingdom of Saudi Arabia under a concession agreement signed in 1949. Out of the six reservoirs in the Wafra field, the most prolific is the Lower Cretaceous Ratawi Oolite.

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.

Horizontal sidetracking and waterflood are part of current Wafra Ratawi reservoir management strategies. These have proven successful to arrest production decline. A comprehensive surveillance program is considered to be the key to optimize waterflood performance. Saturation profile is one of critical parameters to understand waterflood sweep efficiency. The best way to acquire saturation data is by running saturation logs in vertical wells. Since horizontal sidetracking is one reservoir management strategy, the remaining vertical wells accessible for saturation logging are becoming limited and soon will not be available. This paper discusses an innovative and cost effective approach to this surveillance challenge. A combination of permanent fullbore oriented packer and retrievable whipstock, a selective re-entry system, was chosen to complete the wells. The existing vertical wellbore was converted to an observation wellbore before sidetracking. This technique has potential to save significant capital investment by using existing vertical wellbores to serve saturation surveillance purposes. Since the intent is to run saturation logs periodically in the vertical observation wellbore and to produce through the horizontal lateral during normal operation, there are several operational challenges that must be resolved. These mainly include: debris falling during ESP well services, re-entry jobs in horizontal lateral by work string, and effect of squeeze cement operation on cased-hole logs readings. This paper also discusses how the proposed completion techniques overcome these issues. Three wells have been successfully completed with this system. The first time-lapse cased-hole logs were also successfully run in one of these wells, including an attempt to re-enter the horizontal lateral by work string that went smoothly. This unique concept of saturation surveillance wellbore in horizontal producers can also be extended for new drill infill producers completed with cased pilot hole. The technique is considered to be an innovative and first time application across the globe.

Horizontal sidetracking and waterflood are part of current Wafra Ratawi reservoir management strategies. These have proven successful to arrest production decline. A comprehensive surveillance program is considered to be the key to optimize waterflood performance. Saturation profile is one of critical parameters to understand waterflood sweep efficiency. The best way to acquire saturation data is by running saturation logs in vertical wells. Since horizontal sidetracking is one reservoir management strategy, the remaining vertical wells accessible for saturation logging are becoming limited and soon will not be available. This paper discusses an innovative and cost effective approach to this surveillance challenge. A combination of permanent fullbore oriented packer and retrievable whipstock, a selective re-entry system, was chosen to complete the wells. The existing vertical wellbore was converted to an observation wellbore before sidetracking. This technique has potential to save significant capital investment by using existing vertical wellbores to serve saturation surveillance purposes.Since the intent is to run saturation logs periodically in the vertical observation wellbore and to produce through the horizontal lateral during normal operation, there are several operational challenges that must be resolved. These mainly include: debris falling during ESP well services, re-entry jobs in horizontal lateral by work string, and effect of squeeze cement operation on cased-hole logs readings. This paper also discusses how the proposed completion techniques overcome these issues.Three wells have been successfully completed with this system. The first time-lapse cased-hole logs were also successfully run in one of these wells, including an attempt to re-enter the horizontal lateral by work string that went smoothly. This unique concept of saturation surveillance wellbore in horizontal producers can also be extended for new drill infill producers completed with cased pilot hole. The technique is considered to be an innovative and first time application across the globe.