Carbonate coiled tubing (CT) reservoir stimulation approaches vary, using acid systems and different diverters in order to try to achieve the best results. However, because it was not previously possible to know where the injected fluids actually go in the formation during a stimulation job, even with the enhancement of the coiled tubing placement and software model prediction, the results were often not effective as they could be. The inclusion of a fiber optic distributed temperature monitoring system (DTS) in the coiled tubing enables visualization of different zones injectivity by monitoring the exothermal effect of the acid reaction with the carbonate in highest permeability zones and hence acid and diverter placement can be optimized for improved stimulation efficiency. In one of Abu Dhabi Onshore fields a production log (PLT) was run in a water injector well that was completed in two different reservoirs, to provide a baseline injection profile. The acid stimulation job was then performed using fiber optic temperature monitoring through the coiled tubing, to optimize fluid placement. One feature of the data acquired by the fiber optic distributed temperature system was that the initial baseline temperature log was able to identify the high permeability injection interval from its "warm-back" response and this was correlated with the PLT interpretation. Consequently the treatment volume was optimized using the DTS results. Another DTS run was recorded after the acid stimulation with diverter using the injection velocity approach. This consists of bull-heading water down the coil tubing annulus and tracking the hot water generated at the heel of the well from the previous shut-in as it moves across the reservoir. The velocity interpretation of the injection profile confirmed that there was minimal injection into the high permeability interval at that point of time. The stimulation resulted in a well injectivity increase of 20% indicating successful placement and diversion of acid compared to conventional stimulation practices. The use of DTS will enable stimulating wells without the need for pre-job production log (PLT) and especially wells where a PLT is not possible either due to low flow-rates (below critical flow) or operational constrains (completion restriction). This paper details this "first-time" experience of a coiled tubing stimulation combined with DTS measurement and injection velocity profile in the UAE. It also concludes with a list of lessons learnt and recommendations for similar future approaches.
A super Giant field production sustainability is essential and has to be sustained for longer period of time, therefore different techniques have been introduced and tested to overcome the various reservoir issues. Gas Lift technique (GL) has been considered as one of the effective mitigation actions to reactive the dead wells, enhance recovery factor (RF) and accelerate the production from both technical and economical points of view. Prior the full field implementation, it was decided to select a GL Pilot for testing and data gathering, the planned GL Pilot consists of 10 wells which have been selected from various reservoir units and completions to analyze the differences in the performance. The selected Pilot wells were inactive prior to GL implementation (with no oil production) as per set strategy which calls for using of the GL system to reactive the dead wells only.The Pilot started production in November 2008 with almost a total oil production rate of 14 Mstb/d using GL system and the current average rates of the pilot (as of Jan. 2010) are as follow: average oil rate ~ 13,000 bbl/d, average water rate of ~ 19,000 bblw/d, average gross rate of 32,000 bbl/d and average W.C% ~ 60%. The pilot performance was achieved with total gas lift injection ~ 6 MMSCFD (which means 0.6 MMSCFD per well in average). The total oil recovered from the current GL pilot, during a period of one year (330 producing days) is 4.15 MM bbl, this can be roughly turned in to cash amount equal to $ 207.5 MM (assuming 50$/bbl).These resulted values from the GL wells have been surging up and down as a result of the optimization process in order to minimize the W.C% and increase the oil rate. Real Time Optimization (RTO) process is important and currently is ongoing (last stage) to be fully implemented to optimize especially the GL produced water (amount and treatment) in addition to the oil production. Gas quality, availability and conditions have been ensured with the current available field facilities.Pilot Modeling is vital to assess each well behavior, therefore every well has been modeled using Inflow/Outflow Software and pertaining data has been continuously validated and updated according to the production tests and actual findings. Different monitoring tools have been used such as RST, PLT and Gas Lift surveys to identify the actual well performance. The Pilot modeling results have been used as a guidance to predict the full field future GL performance.Generally, the Pilot results revealed the important questions and achieved the core objectives related the GL system for full field implementation.
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