Further development of the fractured Natih field requires a good understaliding of the historical contributiolis from gas/oil gravity drainage and water/oil displacement. A history match of the field has been made using a fractured reservoir simulator, which apart from dual porosity, can model dual permeability and block-blook interaction. Several studies aimed at describing the reservoir in detail were required before simulation could start. The history match shows that gas/oil gravity drainage has been about twice as effective as water/oil displacement. This figure is in good agreement with the gas and water sweep data derived from recent gas saturation and water saturation measurements in the field. Prediction runs show that promoting gas/oil gravity drainage by lowering the fracture oil rim is an attractive way to further develop the Natih field.

This paper was wfectwl for presentation by an SPE Program Committee fallowing review of informatkm contabwd in m abstract wbmlttad by tha author(a). Contents of the paper, s PfeSOIItd, have not &m rwiawsd by tfw Society of Petroleum Engineers end me sub& to cormctlon by the author(s). Tha material, as presented, does not necessarily reflect any paaith of dw Society of Petrdaum Enginows, its officus, or members. Papers pfasemed at SPE meetings we aubjact to publication rwiew by Editorial Committees of rho Society of PatrdmIfn Engimers. Electronic reprc.d~"on, distribution, or storage of any part of this papw for wrnmercial pt.qxxas without the written consent of lfw Scdety of Petroleum Enginmrs is prchlbtted. %rmiuicm to reprcduce in print is restricted to an ebstract of not more than 300 wwds; iflustmticms may not k copied. The abstract must contain conspicuous mknowledgment of whwe and by whom the paper was presented. Write Librarim, SPE, P.O. Sox 833836, Richwdwn, TX 75083-3836, U. S.A., fax 01-972-9S2-9435. AbstractIn reservoirs with a thin oil rim below a gas cap, oil production can be severely hampered by gas coning or cusping problems. Oil production can be improved by means of in-situ generation of a gas-blocking foam barrier in the near wellbore area. Candidate wells in the Eastern Division of shel~PetroIeum Development Company of Nigeria were selected for field testing Gas Shut-Off foam treatments on the basis of high Gas/Oil Ratios (GOR), low BSW, reserves availability etc. Laboratory tests were conducted to identifi suitable foamer systems and construction of reservoir simulation models took place to estimate the potential of the treatments with respect to oil prcxluction and GOR reduction. Eight wells have been treated using two foamer systems and two different foam generation techniques. The results vary between a significant reduction in GOR for more than twelve months, i.e. from 7000 scf/bbl to 2000 scf/bbl at an increased oil rate from 340 to 450 bopd and treatments resulting in a minor GOR reduction for only a few weeks. It can be concluded that, on average the treatments have a 50+ % suc&ss rate.

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The electronic structure of Cu and Cu(Ni)