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- Volume 15, Issue 9, 1997
First Break - Volume 15, Issue 9, 1997
Volume 15, Issue 9, 1997
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4C - new dimension in marine seismic
Four dimensional marine seismic acquisition is set to become an important new tool for specific targets. First Break reports on the circumspect strategy being adopted by PGS Reservoir. It looks increasingly as if the four component (4C) seismic survey acquisition is on the verge of becoming the latest technology battleground for the major seismic contractors in their bid for competitive advantage. Both Western and Geco- Prakla (reported in this month's News Section) are making their first significant moves to offer 4C seismic acquisition to the oil industry. Marking the embryonic stage of the technology Petroleum Geo-Services (PGS) has to date adopted its own distinctive approach. It boils down to not running before you can walk. The company spent two months this summer in the Norwegian North Sea carrying out 150 km of multi-client 2D seismic in three different areas using its own 4C acquisition technique. Data from the surveys is due to be made available this autumn.
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Countering mine dangers that threaten land seismic exploration
The debris of war - minefields, unexploded ordnance and other hazards - have left a lethal legacy which only specialist companies like Exploration Logistics can deal with. The very public - but tragically all too brief - campaign by Diana, Princess of Wales, against landmines left over from armed conflicts worldwide has drawn public attention to a problem all too familiar to the seismic industry. Oil companies are resigned to the fact that seismic exploration and subsequent development can be frustrated by the legacy of war. Mark Tomlins says that around the world there are areas, such as parts of the Falkland Islands, which may be 'off limits' forever. The reason is that during the Falklands war in the 1980s when Argentina tried to occupy the islands, plastic anti-personnel mines were planted over wide expanses of the territory.
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Acoustic monitoring of hydraulic fracture growth
Authors J. Groenenboom and R. RomijnHydraulic fracturing is a technique to improve the inflow performance of oil and gas wells by creating large fractures around the borehole. By doing this, a highly permeable path is created through which the hydrocarbons can flow to the well more easily. The process consists of two phases. In the first phase, a suitable fluid is pumped into the reservoir under great pressure, thereby rupturing the formation and creating fractures. In the second phase, a propping agent, usually a well-sorted sand, is added to the fluid, and after injecting this mixture for some time, the pumps are stopped. The remaining fluid in the fracture leaks away and the fracture closes on the proppant, thus providing the highly conductive path aimed for. The success of fracture treatments depends on our ability to predict and influence the fracture shape and orientation. In the Geometry of Hydraulic Fractures project, sponsored by a consortium of oil and service companies and the Dutch Technology Foundation, the physics of hydraulic fracture growth is being studied. To this end, scaled fracturing experiments are being carried out at the rock-mechanics laboratory at the faculty of Applied Earth Sciences. These hydraulic fracture experiments on model blocks are monitored by an acoustic scanning technique using active transducers. An artificial rock cube (made of cement or plaster) with edges of 0.3 m, is placed in a compression machine to apply an in-situ confining stress. A fracturing fluid is injected through a borehole assembly mounted in the block and eventually a fracture is created inside the block. The fracture grows with a rate of about 0.1 mm s71. After a certain time the pump is stopped (called shut-in) and the fracture is allowed to close again. The total duration of the experiment is in the order of hours. During all stages of fracture initiation, growth and closure, acoustic waves scan the complete block every 30 s. The recording time of a separate scan is in the order of one millisecond, so each one can be regarded as a still picture taken of the growing hydraulic fracture. With 48 transducers scanning the entire block, different combinations of sending and receiving transducers or records, reveal different aspects of the fracture, e.g. radial extent and width. Because we use both P- and S-waves, different features of the scattering of acoustic waves by fractures can be observed. Some aspects of these measurements have been discussed by Groenenboom & Romijn (1996) and Groenenboom et al. (1997a). These laboratory experiments closely resemble seismic monitoring surveys of hydraulic fracturing jobs as performed in the field (Wills et al. 1992; Meadows & Winterstein 1994).
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)