Page 22: of Offshore Engineer Magazine (Jun/Jul 2013)

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Geology & Geophysics

G & G Notebook

Andrew McBarnet

Gravity gradiometry has graduated!

UK-based provider of FTG services, East basin can be calibrated to the FTG data

Andrew McBarnet picks up

African geology, essentially comprising and if necessary, the seismic program on the growing enthusiasm relatively young sediments juxtaposed can be modifed to take account of for modern gravity against a (much denser) Archaean shallow basement or insuffcient depth basement, was ideally suited for grav- of burial of potential source rocks.

gradiometry surveys to ity gradiometry technology. Operators Offshore Mozambique, ENI and assist E&P oil and (Tullow, Africa Oil) have acquired large Anadarko have been leading the charge gas operations

FTG surveys over Kenyan and south- with substantial gas discoveries. In ern Ethiopian holdings to assist their 2011, the Instituto Nacional de Petróle exploration activities. FTG is used (INP), which manages the country’s oil here’s defnitely something to measure variations of the Earth’s and gas resources, announced tenders stirring in the full-tensor grav- gravity feld with such a high degree of for seismic and FTG multi-client sur- ity gradiometry (FTG) market resolution and bandwidth that detailed veys. In April 2013, WesternGeco, win-

T for airborne and vessel surveys over basement structure maps can be de- ner of the main seismic tenders, began onshore and offshore targets, based on rived. This facilitates optimal position- a 2D, long-offset, multi-client survey signifcant advances in gravity mea- ing of a seismic campaign, according to of more than 31,000km. This covers surement for E&P developed in the ARKeX. As an airborne technique, FTG most of Mozambique’s offshore terri- last 15 or so years. Much of the recent surveys can be acquired effciently tory, where future licensing rounds are high-profle activity has cen- and rapidly over large areas with the expected. ARKeX was chosen to carry tered on supporting oil company early additional beneft of a negligible envi- out the FTG multi-client campaign, reconnaissance of prospects in East ronmental footprint. Further down the beginning with a planned survey over

Africa, where identifcation of unsus- line, early seismic the Beira High, but pected new hydrocarbon plays has acquired in a a start date has not taken the industry completely yet been announced. by surprise. The company has

In this context, also been in the bid-

FTG is increasingly ding fray for a similar recognized as a government-inspired valuable method project off Sri Lanka.

to survey large High-resolution, areas of explora- high-bandwidth FTG tion interest where surveys are applicable there is little or no not only to these fron- seismic data avail- tier exploration areas, able and where but have also been large-scale seismic used in areas domi- surveys may be nated by complex salt impractical because structures. For example, of the type and size of ARKeX has carried

Lockheed Martin design full the terrain. out both marine and

According to ARKeX, airborne FTG surveys tensor gravity gradiometer and control cabinet.

OE | June 2013 oedigital.com 24 024OE_0613_gg.indd 24 5/25/13 12:25 AM