Advances in the Application of Biostratigraphy to Petroleum Exploration and Production

Giwa, Gideon Olawumi¹, Adewole Oyede¹, Edward Okosun² (1) Shell Petroleum Development Company, Nigeria, Warri, Nigeria (2) Federal University of Technology, Minna, Nigeria

Petroleum exploration routinely employs biostratigraphic zones in dating rock units. As the world’s hydrocarbon basins mature, most of its subsurface uncertainties lay at reservoir scale, hence the need for a change of strategy in the application of biostratigraphy. This gave rise to the word production biostratigraphy, where biostratigraphy can play a role in reser­voir characterisation, correlation and well site operations. To apply this technique, field spe­cific bioevents are determined and tested for consistency.

North Sea applications resulted in successful re-development of the Gorm field, horizon­tal drilling of a thin 12ft thick Andrew reservoir and the successful appraisal of a Norwegian field. In the Niger Delta, Nigeria, shales within three reservoirs in a swamp field were “fin­gerprinted”. The results showed consistent occurrence of Spiroplectammina wrightii (Syverstril 1905), Eggerelloides scabra (Williameon 1858), Heterolepa pseudoungeriana (Cush 1922) and Lenticulina inornata’d (Orbigny 1846). They provided a framework for cor­relating Maximum Flooding Surfaces, determining facies associations and the option of biosteering is being explored. Biosteering (usually in conjunction with geosteering) is intended to maximise reservoir penetration by biostratigraphically “fingerprinting”, the reservoir-enveloping non-pay stratigraphic units during drilling.

Seismic/sequence biostratigraphy, ecostratigraphy, quantitative stratigraphy and bios­tratigraphic workstations are part of the recent advances that will be highlighted.

The effect of sample storage, type of drilling bit and mud on biostratigraphic analysis will also be discussed.