The paper presents laboratory testing approach to evaluate DIF (Drill-In-Fluid) damage and wellbore cleanup effectiveness in open hole horizontal producer wells. It also investigates the fine movement damage and also the side effect of mud cake removal if it is left in wellbore for long period. The formation damage tests were carried out on sandstone core plugs from 3 different formations with permeability varying from several milidarcy to hundreds milidarcy. The WBM (Water Base Mud) was used with mostly consisted of CaCO3, NaCl, and KCl. Prior to formation damage test, critical velocity test was performed to investigate the fine movement damage. The formation damage tests were started by circulating the mud with 300 - 400 psi overbalance across the core plugs to create mud cake. The mud was then displaced by brine 8.8 ppg and high viscosity fluid was circulated to simulate the real condition in field for hole cleaning process. Several mud cake removals were then circulated and soaked for 1 and 5 days in the system. Finally, the oil return permeability was measured and compared with initial permeability. Throughout the study, it is observed that the critical velocity is mainly controlled by the clay content. Porosity and permeability also plays significant role in the plugging behavior due to fine migration. Acid based mud cake removal can enhance the formation permeability if it is allowed to leak-off through the rock matrix. It also depends on the mineral content of the formation (acid soluble minerals). Delayed acid based mud cake removal outperformed other mud cake removals in this study. The most optimum soaking time using the delayed acid based mud cake removal in this study is 1 day. However, there is no permeability impairment identified if the mud cake removal is left up to 5 days.

The paper presents evaluation of passive ultrasonic logging tool deployed using E-line to assess casing integrity in 3 oil producing wells in South of Oman. In addition a comparison is offered between the ultrasound logging technology and a more conventional well integrity test using a hoist and multi-set plug that has been utilized to date. The ultrasonic log was run in a selection of oil producing wells, operated by beam pump. Those wells were confirmed as having well integrity issues from well surveillance data and were causing significant oil deferment (2.2% of total oil production). Those wells have a history of cementation challenges owning to heavy losses that occur within a water bearing zone located above the pay zone. This, combined with the presence of H2S and oxygenated water at this depth, has resulted in a number of corrosion related integrity issues across the field. The logging program was originally planned inside tubing with surface pressures of 1,800 psi but it was decided to log inside casing (without tubing) because leak was more severe than predicted (1 m3/min of leak rate). In wells A and B, leak points at 630 m and 225 m were identified and respectively verified. However, another leaking interval in well A was also identified from conventional WIT using hoist. In well C, no pressure held on surface causing lack of differential across leak which resulted in identification failure on first attempt (inside tubing). On second attempt (inside casing), unclear ultrasound reading was attained but seven leak points still can be identified after several log passes. The tool can save significant hoist time and will become viable alternative. In conclusion this paper illustrates examples of where the ultrasonic log has provided highly accurate leak detection, significant time saving and improvements in overall operating efficiency. The limits of the technology are also discussed with recommendations provided for the application of the service based on operational experience gained during the technical evaluation.

Good perforating practices are equally important for water injectors as for producers to achieve effective and efficient reservoir pressure support, which, in turn, results in better field productivity. An aspect of good perforating practice is to achieve clean perforations so that the injection skin is minimized. Dirty perforations, whether due to perforation debris or crushed zones around the perforation tunnel can affect a well's injectivity. This problem is further compounded when well injection starts as particles in injection water quickly accumulate at the perforations, causing rapid injectivity drop. Therefore, clean perforations are important to deliver good well injectivity. This is a case study of a wellbore implosion technique on perforations of injector wells in a field in Oman. Compared to perforating in a high-pressure reservoir, achieving clean perforations in a lowpressure reservoir is more difficult as perforating has less potential to breakdown the crushed zone and to purge the crushed material together with the debris from the perforation tunnels. This problem may be overcome by the wellbore implosion technique, using a dynamic underbalance system.Various perforating systems were tried for injector wells in this field. Reactive liner shaped charge, propellant system, and post-perforating dynamic underbalance techniques were used in the same well. A dynamic underbalance gun that creates wellbore implosion was designed, and recorded pressure gauge data were matched to the simulated data. Reservoir properties of each well from the logs and from the well injectivities after applying the above-mentioned perforating systems were compared. As the principle in this case study is perforation cleanup, it is also relevant to producers. It is also relevant to other wells whether on land or offshore, both producers and injectors of any pressure regime that could be suffering from poor cleanup of perforations.

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Increasing oil production and recovery for Heavy Oil can be achieved by reducing oil viscosity. With reference to Darcy law, reducing the oil viscosity results in an increase in oil productivity. The current technologies for reducing viscosity are Steam injection and Miscible Gas (hydrocarbon or carbon dioxide) injection. However both steam and miscible gas has technical and economic limitations, and an alternative technology is required to extend beyond the limitations in both steam and miscible gas injection.The technology described herein is based on reservoir fluid and rock modification by chemical technology approach. Reservoir modifications are made by ability to mix between oil and water, and the mixed viscosity is designed to be reduced to close to, but higher than, water viscosity. Because the viscosity is still higher than water viscosity, the fluid flow becomes slower and will have enough time to react with oil and divert to the oil bank. When the modified chemical is diverted to the oil bank, then wettability alteration acts to peel out oil from the rock surface and has ability to pass through pore throatand hence flow to producing oil well.The research programewasconducted by mimicking reservoir behaviorby implementing mixture viscosity sensitivity performance test, imbibition tube test and coreflood test. The tests are implemented usingactual reservoir oil, water and rock. The result of viscosity reduction is able to reduce oil viscosity from more than 376 cp at reservoir temperature to less than 10 cp mixture viscosity at temperature between 60 and 90°C. For comparison, steam injection is able to reduce viscosity of heavy oil to become less than 10 cp, but requires a temperature of 350°C instead of 60 to 90°C. The imbibition test has shown incremental oil recovery at 14.7 psi (atm pressure) of two times that of reservoir water only, while the laboratory result with coreflood shows additional recovery after chemical injection of 30% to 50% beyond primary and water injection stage.The implementation is technically simple and it is able to be conducted at relatively low cost. The result from implementation by well basis injection yielded a significant increase in oil production. By sharing this road map experience from laboratory result to field implementation of the new method of chemicalstimulation forheavyoil production, it provides an alternative to improve production and recovery of heavyoil, especially in the Middle East.