Offshore production of heavy oil can be challenging due largely to adverse fluid properties, sand production and flow assurance concerns. Recent technology advancements effectively driving management of these challenges and government support through tax relief have significantly contributed to the increased appraisal activity over the last several years in the North Sea heavy oil fields. Application of appropriate technologies and techniques has always been of paramount importance for acquiring high quality information throughout welltest for reservoir characterization at appraisal stage of the fields. It also provides high level of confidence in technology and "proof of concept?? prior to further application in a full field development at investment intensive offshore operating environment.
This paper describes an integrated approach in analytical modeling and design developed and applied in the planning of flow test in a number of North Sea heavy oil fields. This includes a comprehensive pre-evaluation of well productivity, PVT properties modeling as well as design and selection of appropriate artificial lift method. A series of technical solutions considered relevant in relation to enhancing the low flowing well head temperature conditions, typically observed during the cold heavy oil production offshore and often leading to operational constraints on fluid handling capabilities is also discussed. Additionally, a probablistic approach considering base case, low and high case scenarios has been developed and implemented as part of the evaluation process, given the limited amount of available information and high level of uncertainties.
The study demonstrates the benefits of applying analytical techniques for uncertainties handling during flow test planning and thereby enabling accentuation of potential issues, properly planning for mitigation actions and predicting the entire flow test sequence. Finally the study underlines some important guidelines pertaining to planning for further appraisal and development of new heavy oil fields.
Haider, Bader Y.A. (Kuwait Oil Company) | Rachapudi, Rama Rao Venkata Subba (Kuwait Oil Company) | Al-Yahya, Mohammad (Kuwait Oil Company) | Al-Mutairi, Talal (Kuwait Oil Company) | Al Deyain, Khaled Waleed (Kuwait Oil Company)
Production from Artificially lifted (ESP) well depends on the performance of ESP and reservoir inflow. Realtime monitoring of ESP performance and reservoir productivity is essential for production optimization and this in turn will help in improving the ESP run life. Realtime Workflow was developed to track the ESP performance and well productivity using Realtime ESP sensor data. This workflow was automated by using real time data server and results were made available through Desk top application.
Realtime ESP performance information was used in regular well reviews to identify the problems with ESP performance, to investigate the opportunity for increasing the production. Further ESP real time data combined with well model analysis was used in addressing well problems.
This paper describes about the workflow design, automation and real field case implementation of optimization decisions. Ultimately, this workflow helped in extending the ESP run life and created a well performance monitoring system that eliminated the manual maintenance of the data .In Future, this workflow will be part of full field Digital oil field implementation.
The North Kuwait Jurassic Gas (NKJG) reservoirs are currently under development by KOC with assistance from Shell under an Enhanced Technical Services Agreement (ETSA). The fractured carbonate reservoirs contain gas condensate and volatile oil at pressures up to 11,500 psi with 2.5% H2S and 1.5% CO2. This paper describes the planning and implementation of a Well Integrity Management System (WIMS) that allows the safe management of the wells that are being drilled in this hazardous environment.
The wells are designed and constructed in accordance with KOC standards and on transfer of ownership from Deep Drilling Group to Production Services Group have their integrity managed under WIMS. The system is a structured process, relating the frequency and extent of routine monitoring and testing to the particular risks associated with the wells. Compliance with WIMS requirements are routinely reported so that all are aware of the current state of well integrity. WIMS is initially managed through simple spreadsheets and during 2012 is being integrated into KOC's Digital Field infrastructure.
Initially, WIMS has been applied to the range of wells ‘owned' by Production Services Group and tests currently carried out by Well Surveillance Group under PSG's direction. In order to realise the full assurance of safe operation the scope of WIMS application is being extended to the full well population, including suspended wells, and the full range of tests required.
Implementation of WIMS will allow KOC (NKJG) to be able to state that ‘our wells are safe and we know it'.
Vibrations are caused by bit and drill string interaction with formations under certain drilling conditions. They are affected by different parameters such as weight on bit, rotary speed, mud properties, BHA and bit design as well as by the mechanical properties of the formations. During the actual drilling process the bit interacts with different formation layers whereby each of those layers usually have different mechanical properties. Vibrations are also indirectly affected by the formations since weight on bit and rotary speed are usually optimized against changing formations (drilling optimization process). Therefore it can be concluded that for optimized drilling reduction of vibrations is one of the challenges.
A fully automated laboratory scale drilling rig, the CDC miniRig, has been used to conduct experimental tests. A three component vibration sensor sub attached to drill string records drill string vibrations and an additional sensor system records the drilling parameters. Uniform concrete cubes with different mechanical properties were built. Those cubes as well as a homogeneous sandstone cube were drilled with different ranges of weight on bit and bit rotary speed. The mechanical properties of all cubes were measured prior to the experiments. During all experiments, drilling parameters and the vibration data were recorded. Based on analyses of the data in the time and the frequency domain, linear and non-linear models were built. For this purpose the interrelations of sandstone and concrete mechanical properties, drilling parameters and vibration data were modeled by neural networks. Application of sophisticated attribute selection methods showed that vibration data in both, time- and frequency domain, have a major impact in modeling the rate of penetration.
The time taken to safely optimise a reservoir produced by artificial lift can be measured in weeks or months.
Typically the well by well process is as follows:
• Well testing
• Amalgamation of the well test data with down hole gauge and ESP controller data
• Analysis of the data to find the existing operation conditions
• Analysis of the ESP pump curve operating point and optimisation limitations
• Sensitivity studies in software to assess the optimum frequency and WHP
• Notification for the field operations to action the changes
• Further well tests to verify the new production data.
• Analysis of the data to ensure the ESP and well are running optimally and safely at the new set points
New technology enables this process to be performed in real time across the entire reservoir or field, significantly shortening the time to increased production and enabling real time reservoir management.
Each artificially lifted well in the reservoir was equipped with an intelligent data processing device programmed with a real time model of the well. The processors were linked to a central access point where the operation of field could be remotely viewed in real time.
Each well's processor was provided with a target bottom hole flowing pressure to enable the optimum production of the reservoir. The real time system automatically compared the desired target drawdown values with the capability of the pumping system installed in each well, and automatically suggested the optimum operating frequency and well head pressure to achieve the target. Where the lift system was not capable of producing to the target bottom hole pressure, a larger pump was automatically recommended. As production conditions change the system adapted its recommended operating points to compensate and maintain target production.
This paper discusses three case studies where real time optimisation and diagnosis lead to improved production from the reservoir.
In order to develop the design requirement with current regulatory and contemporary HSE practices, for a typical sour oil/gas production facility, a hypothetical case of about 3 mol % v/v H2S in gas and 300 ppm w/w H2S in oil, of multiphase feed stream, has been studied through the dispersion modeling for the conceptual stage. The findings indicated credible downwind lethal / semi lethal threat distance up to 300 meters. The conclusions of the H2S toxic risk assessment combined with the inherent safe design guidelines have yielded an entirely new set of requirement for the risk reduction. To start with it was realized that safe distance control room should be constructed and facilities should be designed for the remote operation, utilizing the new trends of foundation field bus, electronic marshaling and SIL-3 fiber optic sensors. The facility should be access controlled with mandatory PPE requirement of personal H2S monitors and personal quick donning (5 sec) escape SCABA (15 minutes capacity). The centrifugal compressors should be new generation design of enclosed and hermetically sealed type, levitated with magnetic bearing, without dry gas seals and oil lubrication. The vessels should be ASME Section VIII "lethal service?? design and plant piping should be as per fluid category "M?? of ASME B31.3 chapter VIII. Furthermore, stress relieving for thicknesses as low as 10 mm, rather than ASME B31.3 code specified >19 mm would be required. Small valves <4?? sizes should be of forged steel instead of cast steel. The export oil/gas pipelines and flow lines should be designed for =< 50~60 % of SMYS. Plate instead of Shell and Tube Exchangers. Adequate margins between vessels design and operating pressures to avoid PSV chattering. The PSV's to have acoustic monitoring. The facilities should be designed free of valve pits and internal corrosion monitoring pits.
Subsea structures on the seabed may be impacted by free-floating or scouringicebergs. A drift-based Monte Carlo iceberg contact model was developed as partof the SIRAM (Subsea Ice Risk Assessment and Mitigation) program forcalculating iceberg impact risk for subsea structures on the northeast GrandBanks offshore Newfoundland and the Makkovik Bank on the Labrador Shelf. Themotivation for developing this model was to characterize the influence ofbathymetry (i.e., seabed orientation, ridges and basins) on iceberg interactionrates with subsea structures. Results were incorporated into a GIS-basedapplication to allow iceberg contact rates to be calculated for structures witha range of plan dimensions and elevations at various locations.
The analysis of historical satellite data, both radar and optical, areuseful for understanding the nature of ice conditions in Arctic regions andunderstanding the risk they pose for exploration and development. Archivesatellite data are available at no cost and can be analyzed to assess theseverity and variability of iceberg concentrations and their behavior. National ice centres have been providing charts of sea ice conditions, whichcan be analyzed to understand probabilities of encountering ice of variousconcentrations and the lengths of the open water season. The outputs ofthese analyses are useful for understanding the risk of operating in Arcticregions and for developing an ice management plan.
Description. The purpose of this paper is to describe innovativeimprovements to mud pulse telemetry in an ultra deep environment. This alignstelemetry services with the customer need to enhance drilling performancewithout data quality sacrifice through mud pulse technology, providing thecapability of drilling to 15 km and beyond.
Application. The MWD pressure pulse signal suffers attenuation anddegradation while traveling uphole. Echoes and reflections, drill pipe IDchanges, pulsation dampener type and mud plastic viscosity, attenuates thepressure signal up 95% as it reaches surface. Planning becomes keystone for thetelemetry system where;
- Quantification ofsignal attenuation enables a risk managed planning.
- Hardware, improvesMWD Signal detection capabilities.
- Software, allowspractical transmission and bandwidth utilization
Results. This effort resulted in the development of comprehensivemodels for the telemetry signal; as it evolves with depth and is affected bythe different elements of the drilling system.
- Integratingenhancements in software and hardware resulted in doubling of MWD transmissiondata rates.
- Application ofcompression schemes increasing up to 7 times effective transmission speeds.
Significance of subject matter. Successful drilling of deep wellsrelies heavily on the planning stage, to extract the maximum value from thedrilling investment. The initiatives outlined in this paper expand theoperating envelope of the more applicable telemetry technology, supporting thenew depth limits to be set. The effort of this investigation delivered areliable, high band-width transmission system designed for wells targeting 15kmreach and beyond.
In light of the recent increasing interest in the oil and gas developmentsin the arctic region, Huisman Equipment B.V. has developed a Mobile OffshoreDrilling Unit (MODU) named JBF Arctic suited for arctic condition. The stationkeeping in ice is one of the crucial factors determining the feasibility of thedesign. As one of the first steps of the design process ice model tests wereperformed at the Krylov Shipbuilding Research Institute (KSRI) to gain insightin the ice forces acting on the unit. During the model tests the model of theJBF Arctic was retained in a fixed position while being towed through the ice.In reality the station keeping of the unit will be ensured by a mooring system,which has certain flexibility compared to the rigid constrains in the modeltests. This paper elaborates on the creation of a numerical model that canperform time-domain simulations of the dynamic interaction between the vesseland the ice-loads. Using these simulations the mooring system is optimized inorder to cope with the ice loads corresponding to unbroken level ice withthickness up to 3.1m. Several important conclusions were drawn. One is the factthat no dominating frequencies of the ice failing could be identified from themodel tests. This can be explained by a large ratio between the diameter of theunit and the ice thickness. So the ice failure mechanism has a chaoticcharacter. Another conclusion is that the unit does not exhibit significantdynamic behavior. This means that a quasi-static approach can be generally usedfor initial design of the mooring system.
Keywords: ice model test, dynamic ice-structure interaction, ice loadingmodel, mooring system optimization, Arctic MODU.