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Accurate wellbore temperature prediction is essential in deepwater drilling and completion operations. The wellbore temperature profile is the most dominant factor to consider when the cement slurry properties are designed. These properties are critical to ensure the success of cement placement. Many wellbore temperature simulators described in the literature use a finite difference approach in transient temperature profile modeling. However, for deepwater drilling and completion, the process is more complex. Seawater currents and natural convection cannot be ignored in heat-transfer modeling, especially for subsea pipelines and risers. Also, there are few published results of thermal property correlations for non-Newtonian, high-viscosity cement slurry. Special treatments accounting for transient heat transfer for those cases are necessary.Mud and cement slurry are typically pumped at lower flow rates for cementing operations. At these rates, apparent viscosity may be used in heat transfer coefficient calculations. However, rheology properties for non-Newtonian fluids are changed abruptly for different models, and so are simulation results. For high viscosity fluids, such as cement slurry, there is a general need for experimentally derived heat transfer correlations.A novel heat transfer model has been introduced for deepwater cementing. Special considerations for non-Newtonian fluids are included based on theoretical analysis, real field data correlations, and transient heat transfer of deepwater subsea pipelines and risers.The predictions of the wellbore temperature profiles from this model are validated through measured wellbore temperature profiles, both in offshore and onshore cases. The model has been successfully applied in deepwater circulating, cementing, and hydraulic fracturing. Cases will be presented in this paper.
Accurate wellbore temperature prediction is essential in deepwater drilling and completion operations. The wellbore temperature profile is the most dominant factor to consider when the cement slurry properties are designed. These properties are critical to ensure the success of cement placement. Many wellbore temperature simulators described in the literature use a finite difference approach in transient temperature profile modeling. However, for deepwater drilling and completion, the process is more complex. Seawater currents and natural convection cannot be ignored in heat-transfer modeling, especially for subsea pipelines and risers. Also, there are few published results of thermal property correlations for non-Newtonian, high-viscosity cement slurry. Special treatments accounting for transient heat transfer for those cases are necessary.Mud and cement slurry are typically pumped at lower flow rates for cementing operations. At these rates, apparent viscosity may be used in heat transfer coefficient calculations. However, rheology properties for non-Newtonian fluids are changed abruptly for different models, and so are simulation results. For high viscosity fluids, such as cement slurry, there is a general need for experimentally derived heat transfer correlations.A novel heat transfer model has been introduced for deepwater cementing. Special considerations for non-Newtonian fluids are included based on theoretical analysis, real field data correlations, and transient heat transfer of deepwater subsea pipelines and risers.The predictions of the wellbore temperature profiles from this model are validated through measured wellbore temperature profiles, both in offshore and onshore cases. The model has been successfully applied in deepwater circulating, cementing, and hydraulic fracturing. Cases will be presented in this paper.
Clean-up and well start-up operations are often considered as routine operations. This paper provides insights on the proper planning processes to manage several potential contingencies during the initial flow of new wells in deep water environments. Examples of ill-planned operations quantify the downtime, reservoir damage and permanent productivity impairments. A review of the last 25 years of operations in deep water in various regions from the Gulf of Mexico, Brazil, Angola, East African, India, and Black Sea has led to a significant enhancement of the planning processes and execution techniques of initiating and displacing completion fluids out of the well bores. A weighed ranking of the individual causes of operational unconformities provides a prioritization of the necessary contingency plans that need to be addressed. They rank from MetOcean challenges (wind, heave, rain) to human induced activities or to well, reservoir or fluids "surprises". The key to the success of these operations lies mainly in the early determination of the mitigation's procedures. Unplanned shut-in during the early part of the clean-up (less than three hours) can lead to significant back flow of unwanted fluids to the formation and potential damage to the near well bore zone. The initial step of the process involves the ranking of the potential disruption that could occur in the specific operating area/fluid/geology settings. Next, the proposed methodology involves the systematic utilization of transient well bore models coupled with a near well bore model to simulate the various scenarios that may affect the flow. Sensitivities on parameters uncertainties or operational flexibility enable the determination of the worst-likely case scenario and for each of these (or combinations of), a workaround / contingency solution is virtually tested and verified. The cost/benefits of each contingency plan are evaluated and mapped in a traditional risk/frequency matrix. As a support to the well clean-up/start-up, an expected pressure / temperature / rate history is provided with dynamically set high and low alarm levels to enhance the governance of any operational unconformities. Real time monitoring of downhole and surface information allows the confirmation of the status of the clean-up/flowback at all time, and reduces the number of potential contingencies as the well is getting more and more cleaned-up. The paper provides a novel approach to define the global efficiency of clean-up and allows a computation of the environmental footprint of the operation and its contribution in terms of carbon intensity. Wells have been cleaned-up since the beginning of the petroleum industry.
Increasing demand on reliable energy resources have led to an increased exploration activity for untapped hydrocarbon resources in deep-water. The recently discovered, but fast-tracked Turkey's Sakarya offshore natural gas field development is also a result of the country's commitment to energy independence. This paper describes the dynamic reservoir characterization considerations, challenges, and engineering solutions to de-risk field development decisions, confirmed by a well test campaign in a complex setting, with no tolerance to failure. In Sakarya field, a live field development planning approach was applied, where the development plans were updated rapidly, in parallel with the dynamic reservoir characterization process. Therefore, a strong link between static modelling, advanced logging and dynamic well behavior analysis had to be established. In addition, proof of concept for the well completion design had to be validated. Following an unprecedented, detailed formation evaluation, fine-scale reservoir and transient wellbore simulations, five well tests were designed and executed. The design considerations and execution challenges included the completion type, big fluid losses and high risk of hydrate formation in the deep-water environment. Five successful well tests were completed in ultra-deep water and led to the initiation of the first ultra-deep water natural gas field development in Turkey. The detailed formation testing campaign played a key role in selecting production intervals and optimizing well completion. In light of the high-resolution vertical formation evaluation, well tests were designed to prove reservoir extent, connectivity and long-term production potential of the field. Completion design and the actual conditions observed during the execution were compiled and simulated using fine-scale reservoir modeling and transient wellbore simulations to assess all potential risks during well test. The tests were executed successfully, revealing critical well deliverability and reservoir characterization information. Completion brine losses into the formation, hydrate formation risks at low subsea and surface temperatures, completion and formation differential pressure considerations were evaluated with real-time data analysis. Well test execution plan was updated real-time to achieve critical reservoir information. This closely integrated characterization and field development planning approach led to keeping the tested wells as production wells, thus improved efficiency, minimized cost, minimized environmental impact and accelerated time to first production. Many technical challenges and time limitations were overcome during this work. Application of detailed formation testing practices, cased hole gravel pack completion in an offshore environment with hydrate risks and closely integrating the observations with the well test design by a multi-skilled team led to accurate well test simulations, correct test design and successful execution with excellent quality information. This paper allows readers to experience technical considerations in the design and execution steps for successful well test.
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