No abstract

Discoveries in the Faroe–Shetland Basin to date have been made in areas not covered by extensive basalt flows as these flows seismically obscure the geology and structure of the underlying section. The industry has been tackling this problem for many years and it is known that high frequencies penetrate only a short way into the basalt before being scattered, generating high frequency noise. Recent seismic data in Faroes Licence 006 show a dramatic improvement in sub-basalt imaging in this problem area. The improvement comes primarily from processing the data, removing high frequencies (dominantly noise) early in the processing to concentrate on the low frequency data and using careful multiple removal at all stages of the processing. Velocity analysis must be performed as an iterative process and take into account the geological model. Deep towing the source and cable also improves the data by avoiding the higher frequencies that generally cause noise and thereby enhancing the lower frequency signal. Applying these processing techniques to earlier 2D surveys also shows significant improvement in imaging the sub-basalt structure. Data examples show that the sub-basalt structure can now be mapped on the improved data and sub-basalt prospects defined.

This p-wasprepared for pras.ntatmn al the Offshoro Technology Conference he!d ,. Houston T.,as, 6-9 May !S96 Thm paper w= sdected for ptesentat!on by the OTC Prcgram Conmmtee Iolbwmg revmw of misrmatmn crxtamed w a. abstract submsted by the author(s) Contents o! the Dape! as presented. has not been r.wewod by the Oflshom T.i+wwtqy and are subpct to cormci!on by the suthor(s) The malenal as prme.td, does d "ewssanty reflect any pnstiwn of the Oikhore Technology Conference or 11soiimm P@rmnsmn to CVY IS mstvcted 10 an abstract 01 not more than 300 words Illustralmts may nol fw cwmd The abstract should contain czmspmno.s ..knowbdgewnt of where aod by whom I ha pap+?r was prtwnled Abstract This paper will review Statoil's experiences and techniques applied to the mapping of drilling hazards by using exploration 3D seismic data. During the period since first implementing tlus apprortch to shallow gas evaluations, in 1989, the methodology has continued to develop. Attribute mapping techniques have improved the identification of shallow gas and

Exploration in the basalt covered areas of the Faroes offshore has always suffered from poor seismic imaging below the basalt. Long offset 2D and 3D seismic data were acquired and a significant improvement in the seismic image below top basalt has been achieved. Deep towing of the source and receiver cables helped by extending the seismic bandwidth towards lower frequencies. Bubble‐tuned rather than conventional peak‐tuned source arrays gave little, if any, incremental benefit. The improvement in the imaging comes primarily from the approach to processing the data. High frequencies (dominantly noise) are filtered out of the data early in the processing to concentrate on the low frequency data. Careful multiple removal is important with several passes of demultiple being applied to the data using both Surface‐Related Multiple Elimination (SRME) and Radon techniques. Velocity analysis is performed as an iterative process taking into account the geological model. Reprocessing legacy 2D surveys, acquired with wide‐ranging parameters, using these processing techniques improved these datasets significantly, indicating that sub‐basalt imaging seems to be more sensitive to processing than to the choice of acquisition parameters.

Recent developmental and experimental evidence indicates that a semantic strategy probably has priority over a linguistic strategy in sentence perception and comprehension by adults. This investigation was carried out under the assumption that differential effects would obtain in semantic strategy when a task is contrived with major constraints on semantic strategy in the context of a constant operation in syntactic processing. In two studies systematic semantic manipulations were made on the noun in NP2 for unmodified transitive sentences which underwent active to passive transformations in a communicatively sterile context. Plurality, single or double syllables, and derivation type (topical) were not significant morphemic variations on the noun in NP2. However, variations of animateness on the noun in NP3 constituted significant semantic properties in perceiving sentences that underwent active to passive transformations.