Recent Laboratory Investigations of Water Flooding in California

Abstract

Abstract Laboratory flood pot testing of California sands has progressed to aconsiderable extent in the past 18 months. Flood evaluations have been carriedout on over 200 large core samples. Many of these were heavy oil sands of highpermeability and completely unconsolidated in nature. The oil frequently formeda bank, though some of the oil was recovered in the subordinate phase of theflood, by viscous drag. Flood pot recoveries as high as 1400 bbl/ acre ft havebeen recorded. Reservoir analysis suggests a conformance factor of 0.4 toreduce laboratory recovery to probable field practice. Oils with viscosities upto 1800 cp have been successfully handled in flood pot evaluations. Theshallow, loose sands are not well adapted to the application of high pressuresto offset the high viscosities. Introduction Secondary recovery may be said to have started 60 years ago when accidentalfloods occurred in the Bradford sand in Pennsylvania; About 1921 artificiallyconducted water drives came into extensive use and since that time the greatBradford field has been almost completely subjected to water flooding. Duringthe last 30 years, most of the known medium and deeper production in Californiahas been discovered and is being exploited by primary recovery methodssupplemented in some instances by high pressure gas injection. The Californiaarea is just beginning to feel the need for secondary recovery in view of anunprecedented market demand and the rapidly rising cost of new pooldiscoveries. With the presently recognized desirability of secondary recovery inCalifornia, there must also be appreciated a number of serious differencesbetween the water flooding problems here as compared to the territory east ofthe Rockies. California sands are generally thicker, and are frequently softand argillaceous. The oils are often heavier and asphaltic. Much of the oil isbelow 15?API, occurs at shallow depth, is cool and free from appreciabledissolved gas, which results in relatively high reservoir oil viscosity.Secondary recovery is particularly beneficial where primary recovery has beenpoor and where no natural water drive exists. These conditions applyparticularly to the heavy, shallow, clean production from soft, oftenargillaceous California sands so abundantly found at depths less than 1500feet. Often, too, there is a totally insufficient supply of water ofsatisfactory quality to inject at a reasonable cost. Also, the crude oils arepriced far below the premium Bradford crude. T.P. 3640