Experiments performed with distilled water, unconsolidated sand and dead oilfor the purpose of determining the influence of oil flow on the water contentof sands were described. While results found are not necessarily, therefore, identical with those that would be obtained under natural petroleum reservoirconditions, the following conclusions were drawn.When oil under constant head is flowed through an unconsolidated sand, theamount of water retained in the core is inversely proportional to the specificpermeability of the core. This corroborates the view that the degree to whichoil displaces.water out of the pore space is limited by the size of thepores.For the range investigated, the displacing action of a more viscous oil ofhigher specific gravity was found to be the same as a less viscous oil, orlower specific gravity.The amount of interstitial water retained in the sand bears an inverserelationship to the pressure head of the displacing liquid.The degree of retained water saturation of the sand appears to approach 100per cent as the specific permeability approaches zero.For the higher values of specific permeability and for the pressure rangeinvestigated the remaining amount of water in the sand occupies approximately10 per cent of the pore space. This, together with the fact that the limitingoil velocity curve approaches approximately 10 per cent water saturation as anasymptote, indicates that beyond this point removal of water is achieved onlyby a stripping of the grains requiring considerable pressure drops across thesands; or by a balancing of the molecular forces.As the water saturation of the sand exceeds approximately 15 per cent of thepore volume, the permeability of the sand to oil decreases rapidly.Sands with water saturations as high as 40 per cent were found to produce100 per cent oil.
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
A large gas injection program in this unitized field in California has improved gravity drainage, resulting in an ultimate recovery approaching half the oil in place. Deliberate water production has reduced a natural water influx that would have reduced recovery if not checked. Few "giant" oil fields can match the performance of the Coalinga Nose field. Introduction The Gatchell pool of the Coalinga Nose field provides a 34-year case history of a gravity drainage reservoir. The field is approximately 6 miles northeast of the town of Coalinga in Fresno County, Calif. After 12 years of competitive operations, the field was unitized in 1950. The most unusual feature of the Gatchell pool's production history is that since unitization, it pool's production history is that since unitization, it has been operated in a manner to maximize the gravity drainage potential and arrest natural water encroachment. Crestal gas injection was begun in 1950 and has continued to the present. A pilot waterflood was attempted but was short lived because it proved less efficient than gravity drainage. Further, large volumes of water have been produced from edge wells to prevent natural water encroachment from reducing recovery. In 1969, the gas injection was supplemented with a large-scale program of nonindigenous-gas injection. More than 58 Bcf of natural gas has been injected under this program. Cumulative oil production exceeds 425 million bbl, or 42.7 percent of the production exceeds 425 million bbl, or 42.7 percent of the original oil in place, and the current production is about 10,000 BOPD. An ultimate recovery of 470 million bbl, or 47.2 percent of the oil in place, is expected; this is an increase of 79 million bbl over the calculated primary recovery. Development History and Method Of Operation The pool was discovered with the completion of well Gatchell No. 2 (now 1-18F) on June 26, 1938. Development progressed rapidly until Dec. 1941, at which time 157 wells had been drilled. Most of the field was developed on 20-acre spacing, but some closer spacing along the east flank and the southwest area has reduced the average spacing. A total of 192 wells had been completed as of July 1, 1972. In June of that yea, 75 of those wells were active producers, 21 were used for gas injection, 15 had been abandoned, and 81 were idle. During World War II the maximum efficient production rate (MER) for the pool was set by the production rate (MER) for the pool was set by the Petroleum Administration for War (PAW). Petroleum Administration for War (PAW). Controversy between the PAW and the operators developed over what the proper production rate should be to minimize pressure decline. MER's set during this period ranged from 15,000 to 50,000 B/D. To meet period ranged from 15,000 to 50,000 B/D. To meet the wartime demand, production in excess of the MER was permitted to as high as 59,000 bbl. The MER was 30,000 B/D when the PAW was dissolved on Sept. 30, 1945. MER recommendations were made by the Conservation Committee of California Oil Producers as the successor of the PAW. From 1945 until 1953 the operators produced at rates ranging from 43,000 to 54,000 B/D. The production history for the pool is shown graphically in Fig. 1. JPT P. 1147
EFFECTIVE sand permeabilities can be ascertained from core analysis if the laboratory data are compensated to allow for the presence of connate or residual water, Such adjustments can be made by applying empirically derived correction factors.Effective sand permeabilities can be estimated also from analytical studies of field depth-pressure measurements. In one method the time rate of pressure build-up after a well is shut in from steady-state flow is required, and in the other the direct measurement of a steady-state rate of flow and the corresponding equilibrium pressure.The results of the investigation discussed in this paper demonstrate that these methods for determining mean effective sand permeabilities can be correlated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.