The paper discusses conceptualization, design and implementation of the first ever inflow tracer technology application in UAE carried out in an Abu Dhabi offshore field. Working in offshore environment has challenges related to operations, cost, resource requirements and HSE that requires innovative and cost-effective solutions to improve efficiency. In recent years, controlled release smart tracers have carved out a niche as a proven solution for extended life fluid flow monitoring, thus allowing the engineers and geoscientists to better understand fluid inflow patterns in a well leading to informed decisions on reservoir management and production optimization. Smart tracers have the capability to detect, quantify and monitor phase breakthroughs and understand subsequent influx behavior in the well. Being a pioneer project, critical focus was placed on design, execution, and cost optimization. Smart tracer technology was chosen over conventional production logging as it provided production profile monitoring over time compared to single time measurement when using production logging, substantially lower operating cost as well as no production intervention. A flowback calculation was used inputting static and dynamic reservoir data to understand the flow dynamics that the tracers would encounter. Reservoir permeability profiles, image logs and hole rugosity were utilized to identify potential areas of influx along the wellbore and strategically place specially designed smart oil and water tracers along the ~3300 feet long lateral. Strictly adhering to local environmental regulations, a thorough offshore job hazard analysis was carried out and a risk matrix was framed. A specialized first of a kind closed loop customized sampling procedure was invented to de-risk a hydrogen sulfide (H2S) hazard present during sampling operations. The paper describes the initial results for the first well in the campaign. Sampling strategy consisted of two phases: high-frequency immediately after well commissioning followed by steady state sampling. Samples were collected at the wellhead and analyzed for tracer breakthroughs. Results showed a good calibration with conventional production logging, confirmed well clean-up and yielded crucial information on zonal flow contribution. Utilizing a local cost model, smart tracer technology was found to offer typical cost savings in the order of US$10 million for a ten well program over five years as compared to conventional production logging. The paper offers insights into the first application of controlled release tracers in offshore Abu Dhabi highlighting the best practices in project design, techno-economics, hazard analysis and operational excellence. The success of the project is the first major step towards embracing this advanced technology for reservoir monitoring and surveillance. This opens opportunities for similar applications elsewhere with significant potential to incentivize life-cycle cost of reservoir management and improve hydrocarbon recovery.
Carbonate reservoirs have complex pore structures and serious heterogeneity, which increase the difficulty to achieve efficient oilfield development. Conventional core plugs cannot accurately depict the heterogeneity characteristics that may beyond the scale of plugs. Thus, whole core experiments are conducted to better study this issue. The methodologies involved in this study include experimental study, outcrop observation, statistical analysis, and numerical modeling. 18 whole core sections are collected from a giant cretaceous carbonate reservoir located in the Middle East, and the OOIP of this carbonate is 4000 MM bbls. We conducted 3D CT, whole core experiments, and plug experiments for the total of 18 sections of the core. Furthermore, numerical simulation is conducted to better evaluate the impact of heterogeneity. After integrating results from all these methodologies and technologies, 2D and 3D CT images, horizontal permeability, vertical permeability, and density of whole core, horizontal plug, and vertical plug are obtained. Then, pore structure visualization and experimental results are combined, and analysis was carefully conducted. Results show that whole core can better depict the reservoir heterogeneity, and some interesting observations were found, such as when the permeability of the core section is low, permeability of whole core is greater than that of plugs; whereas when the permeability of the core section is high, permeability of whole core is lower than that of plugs. Simulation results indicate that heterogeneity is one of the major factors determining the performance of carbonate reservoirs. This study offers detailed evidence to support engineers and geologists for better understanding the heterogeneity and optimizing production plan on the carbonate reservoir.
Understanding the heterogeneity is critical for a successful water injection in a carbonate reservoir. Thief zone is one of the most obvious forms of heterogeneity, which indicates the thin layer with higher permeability compared with average reservoir permeability. The existence of thief zone results in earlier water breakthrough and faster water cut increase, which lead to smaller sweep efficiency and lower recovery factor. Therefore, determining the thief zone distribution and proposing corresponding development plan are very important.This paper focuses on a super-giant carbonate reservoir, which is a Cretaceous carbonate reservoir in Middle East, with an OOIP of more than 20 billion barrels. Thief zones are widely distributed in this carbonate according to the production logging test (PLT). In this paper, we combined geological understanding and dynamic behavior to summarize different types of thief zone distribution, which means the different locations and scales of thief zone and barriers. Then, geological model is built, and reservoir simulation is conducted on the models corresponding to different types to optimize the development strategy.The optimized parameters include well pattern and perforation strategy. Then, development strategies are proposed for different types of thief zone distribution. Results indicate that location of thief zone hasobvious impact on the production. In order to mitigate the impact of thief zone, line drive pattern is preferred when the permeability ratio is high. Most importantly, different types of thief zone distribution require specified perforation strategy, and optimizeddevelopment strategies could save more than 25% of injected water by mitigating the futile cycle of injected water.This paper offers a case study that summarizes different types of thief zone distribution and optimizes the development strategy for different scenarios. It also provides a methodology and reference case for engineers and geologists to develop other similar fields.
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