LAND SUBSIDENCE
1. Feasible to apply the same concept of ‘consolidation’ (associated with the drainage of a clay layer) - used in soil mechanics - for assessing the compaction - associated with a petroleum reservoir?
If yes, then, would it remain feasible to ensure that the ‘reservoir fluid compressibility’ would remain much smaller than the ‘reservoir rock compressibility’ associated with the reservoir?
Also, how to deduce the ‘fluid density’ associated with the estimation of ‘coefficient of consolidation’ for an oil-water system?
2. Whether the ‘centers of subsidence’ really coincide with the ‘centers of production wells’ associated with an oil field?
3. Despite the depositional environments @ various subsidence sites in the vicinity of a wellbore at the surface level remains varied, could we still expect a thick sequence of either an unconsolidated or poorly-consolidated sediments (which essentially forms an interbedded permeable-semipermeable system) within the reservoir thickness of a petroleum reservoir during hydrocarbon production?
What will happen if a relatively large fraction of the reservoir thickness (or width) consists of highly-compressible clay in the context of land subsidence?
Even otherwise, focusing on reservoir seals, if the seal consists of significant clay with swelling properties, then, won’t the ‘total potential compaction of reservoir seal’ remain to be greater than the ‘compaction of the reservoir’ (assuming the compressibility of clay to remain a couple of orders of magnitude greater than the compressibility of the sand)?
If (a) the intrinsic permeability of clay remains to be several orders of magnitude less than the reservoir permeability; and also, if (b) the compaction in reservoir results from the drainage of both the brine and hydrocarbons, while the compaction from seal remains associated only with the brine drainage; then, how do we take into the simultaneous compaction of both seal and the reservoir?
4. Can we distinguish ‘seal compaction’ resulting from ‘seal compressibility’ and its associated ‘changes in effective stress in seal’ – from that of ‘reservoir compaction’?
5. To what extent, ‘water flooding’ would be able to arrest ‘land subsidence’ by means of ‘enhancing the potentiometric heads in the reservoirs’ causing ‘an expansion of reservoir’?
6. Feasible to learn the essence of ‘mitigating the rate of subsidence’ from ‘Wilmington Oil Field’ (located in Long Beach, California) case study?
7. Feasible to correlate ‘hydrologic model’ (potentiometric-surfaces/drawdowns at the basin scale) with the ‘subsidence model’ associated with a petroleum reservoir?
Not necessarily - compaction and induced subsidence will in principle be controlled by the combination of pressure depletion, reservoir thickness and reservoir consolidation. These parameters do not necessarily coincide with the centre of surface production. This es especially the case if field development is with deviated or horizontal wells.
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