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Kuwait's first smart Level-4 multilateral well was completed in the Burgan reservoir by combining a Level-4 junction with stacked dual-lateral completion with a customized viscosity-independent inflow-control device (ICD), two customized inflow-control valves (ICVs), downhole gauges, a wide-operating-range electrical submersible pump (ESP), suitable wellheads, a tree, and integrated surface panels for real-time data monitoring. The smart multilateral well has assisted in addressing premature water breakthrough, has enhanced water-free oil production, and has facilitated uniform depletion, which results in improved hydrocarbon recovery. The Minagish field in west Kuwait (Figure 1) is a north/south-trending anticline with hydrocarbon contained in six major reservoirs (sandstone and carbonate) ranging in age from Early Jurassic to Late Cretaceous. The Burgan sandstone reservoir lies at the crest of the Minagish field. The lower section of the Burgan sandstone reservoir consists of a braided river system with stacked-channel sand bodies that have very high horizontal and vertical permeability (on the order of a few darcies) and are associated with an underlying active aquifer.
In coning situations, such as in the production of oil reservoirs with a bottom aquifer, multilateral wells reduce the coning effect and, hence, prove to be more cost-effective. This paper discusses the first multilateral well with a Level-4 junction combined with an inflow-control device (ICD) planned, designed, and drilled in the Upper Burgan reservoir of Raudhatain field, north Kuwait. The paper covers the main challenges of well placement during geosteering to ensure the best quality of reservoir rock in structurally and depositionally complex settings with smart-completion design. The Raudhatain oilfield structure is one of several developed along a prominent anticlinal ridge that plunges gently north of Kuwait. These individual highs, in which the principal oil accumulations of the area are localized, tend to be of large areal extent and substantial structural relief.
Dilib, F.A.. A. (Imperial College London) | Jackson, M.D.. D. (Imperial College London) | Zadeh, A. Mojaddam (Statoil) | Aasheim, R.. (Statoil) | Årland, K.. (Statoil) | Gyllensten, A.J.. J. (Statoil) | Erlandsen, S.M.. M. (Statoil)
Summary Important challenges remain in the development of optimized control strategies for intelligent wells, particularly with respect to incorporating the impact of reservoir uncertainty. Most optimization methods are model-based and are effective only if the model or ensemble of models used in the optimization captures all possible reservoir behaviors at the individual-well and -completion level. This is rarely the case. Moreover, reservoir models are rarely predictive at the spatial and temporal scales required to identify control actions. We evaluate the benefit of the use of closed-loop control strategies, on the basis of direct feedback between reservoir monitoring and inflow-valve settings, within a geologically heterogeneous, thin oil-rim reservoir. This approach does not omit model predictions completely; rather, model predictions are used to optimize a number of adjustable parameters within a general direct feedback relationship between measured data and inflow-control settings. A high-resolution sector model is used to capture reservoir heterogeneity, which incorporates a locally refined horizontal grid in the oil zone, to accurately represent the horizontal-well geometry and fluid contacts, and capture water and gas flow. Two inflow-control strategies are tested. The first is an open-loop approach, using fixed inflow-control devices to balance the pressure drawdown along the well, sized before installation. The second is a closed-loop, feedback-control strategy, using variable inflow-control valves that can be controlled from the surface in response to multiphase-flow data obtained downhole. The closed-loop strategy is optimized with a base-case model, and then tested against unexpected reservoir behavior by adjusting a number of uncertain parameters in the model but not reoptimizing. We find that closed-loop feedback control yields positive gains in net-present value (NPV) for the majority of reservoir behaviors investigated, and higher gains than the open-loop strategy. Closed-loop control also can yield positive gains in NPV even when the reservoir does not behave as expected, and in tested scenarios returned a near optimal NPV. However, inflow control can be risky, because unpredicted reservoir behavior also leads to negative returns. Moreover, assessing the benefits of inflow control over an arbitrarily fixed well life can be misleading, because observed gains depend on when the calculation is made.
This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 175227, “Optimize Development Strategy of Upper Burgan Reservoir Through Multilateral Well With Inflow-Control Device in Raudhatain Field, North Kuwait,” by Sankar Chowdhuri, Peter Cameron, Tarek A. Gawwad, Mohammad R. Madar, Siddhartha Sankar Sharma, Moute’a Dughaim AlMutairi, Vijay Shankar Rajagopalan, Suresh Chellappan, and Moudi Fahad Al-Ajmi, Kuwait Oil Company, prepared for the 2015 SPE Kuwait Oil & Gas Show and Conference, Mishref, Kuwait, 11–14 October. The paper has not been peer reviewed.
In coning situations, such as in the production of oil reservoirs with a bottom aquifer, multilateral wells reduce the coning effect and, hence, prove to be more cost-effective. This paper discusses the first multilateral well with a Level-4 junction combined with an inflow-control device (ICD) planned, designed, and drilled in the Upper Burgan reservoir of Raudhatain field, north Kuwait. The paper covers the main challenges of well placement during geosteering to ensure the best quality of reservoir rock in structurally and depositionally complex settings with smart-completion design.
The Raudhatain oilfield structure is one of several developed along a prominent anticlinal ridge that plunges gently north of Kuwait. These individual highs, in which the principal oil accumulations of the area are localized, tend to be of large areal extent and substantial structural relief. The Raudhatain structure exhibits a quasiradial pattern of small normal faults of limited throw. This geometry suggests a primary origin by uplift.
The Raudhatain structure is a faulted anticlinal dome with 65 to 90 ft of topographical relief. The 3D seismic has defined the major faulting in the northern part of Raudhatain as northwest trending, whereas in the southwestern part of the field the faults trend northwest. Fault throws are highly variable and range from less than 30 ft to as much as 150 ft.
Stratigraphy of Upper Burgan Reservoir
The Burgan formation is a major reservoir unit. It unconformably overlies the carbonate Shuaiba formation and underlies the Mauddud carbonates with locally unconformable contact. The thickness of Burgan is approximately 950 ft of soft, clean, porous, well-sorted quartz sandstones of littoral to possibly deltaic aspect, interbedded with siltstones and dark shales. The Burgan formation at Raudhatain has been divided informally into three members, termed the Upper Sand, Middle Shale, and Lower Sand.
Technology Focus The past year has experienced dramatic changes in industry activities. Despite the downturn, it has been encouraging to see that there has remained an active interest through various industry events and discussions in improvement in the delivery of complex wells. I had the opportunity to participate in several SPE Advanced Technology Workshops (ATWs) and Forums related to this topic, and it was great to see record attendances, which provided for a diverse, yet high-quality, discussion and interaction. Design factors, improving drilling execution, and complex-well design, along with maximizing reservoir contact for horizontal and complex wells, are still major industry drivers, even though the industry has already drilled and completed many thousands of these wells. Every year, new technology enters the market place providing potential for improvement of all aspects of horizontal-well operations, but on the basis of excellent and open discussions at SPE events, there still are further challenges to overcome. Conclusions from several meetings included positive reactions to the introduction of new technologies in helping drive performance to new levels, but it was highlighted that the repeatability depended upon good knowledge capture and transfer of learning. Development of the structured approach, focused on continuous improvement, is as relevant today as it was 20 years ago. This message was echoed at all ATWs and Forums. The reduction in nonproductive time and overcoming operational challenges through better planning, although well known, are still a required focus. As the industry adapts to a constantly evolving horizontal- and complex-well environment, positional accuracy and placement of the well trajectory are critical to better reservoir contact and production. One interesting conclusion was that the successful drilling of many highly challenging wells appears to have been taken for granted. However, delivering the completion phase on long-stepout wells and management of the reservoir remain challenges for the future. Horizontal and Complex-Trajectory Wells additional reading available at OnePetro: SPE 118809 • "Beyond the Technical Limit: Turbodrilling—A Paradigm Shift to World-Class Horizontal-Well Construction" by Todd Mushovic, BP plc, et al. SPE 119599 • "Inflow-Control Device: An Innovative Completion Solution From Extended Wellbore to Extended Well Life Cycle" by Saif Ali Al Arfi, ADCO, et al. SPE 120579 • "A Comparison Between Multifractured Horizontal and Fishbone Wells for Development of Low-Permeability Fields" by Xiance Yu, University of Louisiana at Lafayette, et al. SPE 123008 • "First Applications of Inflow-Control Devices (ICDs) in Openhole Horizontal Wells in Block 15, Ecuador" by P. Roman, Petroamazonas, et al. OTC 19910 • "The Longest Challenge: Overview of a Groundbreaking Horizontal Well in Gimboa Field, Angola" by K.D. Contreiras, Sonangol Pesquisa & Produção, et al.