Time-lapse or 4D seismic surveys could extend the life of gas reservoirs by identifying bypassed accumulations and identifying flow barriers, a new study has shown. A paper based on rock property work in BP Egypt’s Ha’py field in the Nile Delta suggests the same time-lapse seismic data that has proved successful in the cost-effective management of oilfield reservoirs could equally apply to gas fields.
“Although the 3D effects will be smaller they should still be visible, especially in shallow gas reservoirs,” said the paper’s author, Robert Francis Marten, a geophysicist with BP Egypt. Marten’s modeling study has been awarded the American Association of Petroleum Geologists (AAPG) 2002 Gabriel Dengo Memorial Award, to be presented in Salt Lake City USA in May.
“The science behind 4D seismic research is beautifully simple: as oil or gas is produced the reservoir experiences pressure and saturation changes. When these changes are large enough repeat seismic surveys can track flood fronts and recognize barriers and bypassed pockets, which will have significant commercial benefits,” said Marten.
The modeling studies were carried in relation to Pliocene reservoirs in the Nile Delta where 14 trillion cubic feet of gas has been discovered and current production comes from numerous fields.
The paper was first presented at the Cairo 2002 conference in October last year when local geophysical societies (EPEX, EGS) combined with the might of the international geo-technical societies (AAPG, SEG, EAGE) to present a powerful showcase of new technologies in use in the Middle East and Africa. — (menareport.com)
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