The development of present methods has been a gradual outgrowth of extensiveobservation, both scientific and practical, of conditions surrounding theaccumulation and extraction of oilbodies. Until comparatively recently, ourknowledge of many of these factors had hardly gone beyond the experimentalstage. We are now well into the transitional period between the experimentaland practical, and it appears certain that the use of the gas, air, waterdrives, possibly the mining process and improvement of operating equipment havebeen developed to a point where their commercial application on a large scalewill bring satisfactory results, having a wide and lasting effect on the oilindustry throughout the world. Because of its comparative newness and itsappeal to the imagination, the restoration of rock pressures is more in thepublic eye than are many routine production processes and methods that may beof equal or greater aggregate importance and which must be extended and furtherimproved to keep pace with the times. Inasmuch as we are now concerned with thesalvaging of oil in developed pools, no consideration will be given to newproperties.

In many of the so-called "hydrostatic" or natural water-drive pools, the existing well spacing is such that it is highly probable that maximumrecoveries, under present methods, are not being obtained. Large quantities ofwater carrying comparatively small amounts of oil, handled with present liftingmethods, bring such limited returns that additional expenditures in new wellsand equipment apparently cannot now be justified from a ledger standpoint. Itis reasonable to suppose that coning has taken place in many wells of thischaracter and particularly so in wells, which may have bottom waterdifficulties. In many cases, the sands may be water-logged. This hasundoubtedly curtailed production in many instances but the measure of the wellsunder these conditions should not be necessarily accepted as a measure of theproductive possibilities of the sands. Many of us can cite specific instancesof profitable late close-drilling in water-flooded areas and also instancesthat might justify additional drilling.

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