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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 171510, “Cluster Liquefied Natural Gas: New Paradigm for Small and Medium Liquefied-Natural-Gas Business,” by JungHan Lee, LNG Solutions, prepared for the 2014 SPE Asia Pacific Oil and Gas Conference and Exhibition, Adelaide, Australia, 14–16 October. The paper has not been peer reviewed.
Small- and medium-scale liquefied natural gas (LNG) is different from conventional LNG in trading distances, target markets, and application areas. Small- and medium-scale LNG may better coordinate needs between regional gas producers and consumers. Cluster LNG is a new concept of LNG technology suitable for emerging market environments. High performance of cluster LNG originates from higher liquefaction temperature and the adoption of efficient refrigerants for the temperature ranges. The inherent high performance of cluster LNG enables low capital expenditure (CAPEX) and low operational expenditure (OPEX).
Small-scale LNG has so far constituted only a minor portion of global LNG production. However, there are many necessities of regional energy infrastructures and technologies that are different from those of traditional LNG. In Southeast Asian countries, natural gas and LNG sometimes compete with diesel oil rather than large-scale pipeline gas or large-scale LNG. At the same time, there are many small scattered gas sources remaining to be monetized for domestic markets in the region. Nevertheless, these domestic gas fields have not been developed properly so far because of small units of production and, as a result, high cost per unit. In this regard, new technologies suitable for small- and medium-scale LNG development may be necessary.
LNG for global exports and LNG intended for regional demands may need different approaches. Typical large-scale LNG aims to export at a radius up to 10 000 km; on the other hand, small- and medium-scale LNG may need only a 500- to 2 000-km radius.
Takeuchi, Takahiro (Hachinohe Institute of Technology, Japan) | Nakazawa, Naoki (Forest Works Inc., Japan) | Kawamura, Muneo (Shimizu Corporation, Japan) | Sakai, Masafumi (Taisei Corporation, Japan) | Akagawa, Satoshi (Hokkaido University, Japan) | Saeki, Hiroshi (Hokkaido University, Japan)
A series of ice indentation tests has been performed since the winter of 1996 at Lake Notoro in Hokkaido as part of the JOIA project (JOIA reports 1996-99). The main factors affecting total ice load (F) on a structure were investigated using data derived under systematic test conditions, using natural sea ice. The width (W) of the model structure, ice thickness (h), indentation speed (V) and uni-axial compressive strength (σc) are the major factors influencing ice load on a structure with a vertical face. This paper determines that indentation pressure (Pt) depends on (W/h), (V/h) and (h). It also describes the pressure distribution examined by the 2-dimensional panel sensor, which can measure pressures in 2112 points at once, depending on various indentation speeds.
In progress since 1995, the JOIA project undertakes to determine the scaling effect of ice load.. In medium-scale field indentation tests (MSFIT), as a part of the project, a lot of local iceload data as well as total ice-load data was obtained through load cells attached to a 100-mm-wide surface panel of a model structure in contact with an ice sheet. In the winter of 1998, a 2- dimensional panel sensor that can measure pressures of around 1936 points (44 rows, 44 columms) per panel (smaller panel) was also used to determine the ice failure pattern in addition to local ice pressures. These results were reported in Takeuchi et al., 1997, 1998, 1999; Saeki et al., 1998; and Sodhi et al., 1998. Width (W) of the model structure, ice thickness (h) and indentation speed (V) were varied as main parameters influencing total ice load and ice failure mode in the test series. In particular, in the 1999 winter tests, thicker ice and a wider range of indentation speeds were considered, and also a larger 2-dimensional panel sensor was attached to measure ice pressures for thicker ice.
Birajdar, Pranav R. (Memorial University of Newfoundland) | Taylor, Rocky S. (Memorial University of Newfoundland, C-CORE Center for Arctic Resource Development) | Hossain, Ridwan B. (Memorial University of Newfoundland)
For ice-prone offshore regions, the study of dynamic ice loads and associated mechanics is highly important. Dynamic ice-structure interaction processes are complex and while significant gaps in understanding remain, research is underway to help provide insights into the coupling mechanisms that can result in dynamic excitation of structures over a range of interaction scales. The present paper is focused on an analysis of selected results from a series of medium-scale laboratory tests in which the effects of structural compliance on observed interaction processes and associated loads are considered for indenters on two configurations of the test structure: mounted on a compliant beam; and mounted on the rigid cross-head. The effect of ice temperature and indenter size on these results are also discussed.
When ice sheets interact with fixed offshore structures, ice crushing failure can result in dynamic ice forces that may induce structural vibrations. These dynamic ice actions on offshore structures are a significant concern for platforms designed for Arctic conditions. Ice-induced vibrations on vertical-faced structures in ice-covered waters have been a known challenge since the first observations of ice induced vibrations on the drilling platforms in Cook Inlet, Alaska by Peyton (1968) and Blenkarn (1970). Since then, ice loads and structural vibrations have been reported on lighthouses (e.g. Määttänen, 1975; Engelbrektson, 1977; Määttänen, 1978; Björk, 1981), bridge piers (e.g. Neill, 1975; Sodhi, 1983) and offshore jacket oil platforms (e.g. Yue et al., 2001). Ice-induced vibrations were also observed on multi-legged structures in the Bohai Sea (Xu et. al., 1986) that led to harmful resonant vibrations. Initially, it was believed that ice induced vibrations are a problem only for narrow and slender structures. In 1986, the Molikpaq, a massive caisson structure deployed in the Beaufort Sea, experienced highly dynamic ice loads and steady-state vibrations in such range that it resulted in partial liquefaction of the sand core leading to evacuation of the platform (Jefferies and Wright, 1988). Phase-locked ice crushing behavior had previously only been considered for narrow structures having low aspect ratios, but the Molikpaq incident expanded the scope of study of dynamic ice-structure interactions to include wide structures and larger interaction scales. These observations have highlighted the importance of considering dynamic effects and has stimulated much research to help fill knowledge gaps regarding the underpinning physics, which is essential in supporting the development of next generation engineering methods for safe, economic design of offshore structure.
Takeuchi, Takahiro (Shimizu Corporation) | Masaki, Takaharu (Hokkaido University) | Akagawa, Satoshi (Shimizu Corporation) | Kawamura, Muneo (Shimizu Corporation) | Nakazawa, Naoki (Pacific Consultants Co.) | Terashima, Takashi (Pacific Consultants Co.) | Honda, Hideki (Hokkaido University) | Saeki, Hiroshi (Hokkaido University) | Hirayama, Ken-ichi (Iwate University)
Liang, Xing (Zhejiang Oilfield Company, PetroChina) | Liu, Xiao (Schlumberger) | Shu, HongLin (Zhejiang Oilfield Company, PetroChina) | Xian, ChengGang (Schlumberger) | Zhang, Zhao (Zhejiang Oilfield Company, PetroChina) | Zhao, ChunDuan (Schlumberger) | Li, QingFei (Zhejiang Oilfield Company, PetroChina) | ZHANG, Lei (Zhejiang Oilfield Company, PetroChina)
Abstract The Silurian LongMaXi gas shale in the Sichuan basin is an emerging play in China. It experienced multiple major tectonic evolutions with uplifting and burying sequences in its geological time. As expected, this shale could develop tremendous small-scale discrete natural fractures (DNF) like many other notable North American gas shale plays. But only sparse DNFs were observed from several borehole images in a shale gas field. This paper presents a case study for characterizing complex multiscale natural fracture systems of the gas shale. In the study, natural fracture systems were classified as four types: large-scale faults, medium-scale fracture systems (including microfaults and crushed zones or fracture corridors), small-scale DNFs, and micro-scale fissures per their correspondingly scale-associated geological, geophysical, and petrophyscial features and responses. An optimized ant-tracking approach was implemented to track seismic abnormities and discontinuities as indicators of subseismic medium-scale fractures. Key components of this approach include optimized seismic gathers' angle-range, optimal scanning directions and angles, parameter adjustment criteria, and a comprehensive QC process. The QC process, which considers regional geological and tectonic evolution, fracture mechanical mechanism under strike-slip stress regime, and observations from all available resources, was implemented on each identified medium-scale fracture zone to ensure its reliability. This paper has more focuses on characterizing the medium-scale fracture system because of which can be a unique feature of LongMaXi gas shale compared to its North American counterparts. Characterizing of this medium-scale fracture system considers factors including fracture development mechanism and fracture pattern under strike-slip condition, structure control and curvature tendency, and intensity and amplitude of seismic discontinuity and abnormities. The study shows such medium-scale fractures are widely distributed across the study field. Complexities encountered while drilling and stimulation such as heavy mud loss or screen-out due to unexpected high leak-off rate had strong correlation with them. Two principle orientations of the medium-scale fractures were identified and further validated by outcrop observations and microseismic events observed from hydraulic fracturing monitoring. The study suggests that such medium-scale fractures may be mainly controlled by two major tectonic events during Himalayan movement because their principle orientations are almost exactly following the directions of two major tectonic movements. In combination with all types of natural fractures as defined, 3D multiscale natural fracture model and Geomechanical Earth model were established, which are two keystones for drilling quality and completion quality for further applications. These medium-scale fractured or crushed zones along with large-scale faults and small-scale DNFs across this shale gas field could significantly impact on efficiency and effectiveness of development. In particular, to understand how hydraulic fractures interact with such medium-scale fractures will be essential.