|Publisher||Society of Petroleum Engineers||Language||English|
|Content Type||Conference Paper|
|Title||The Use of Density Control Foam Fracturing for Selective Proppant Placement in the Bartlesville Formation|
|Authors||Barber, P.L., ARCO Oil and Gas Co.,; Themig, D.J., Halliburton Services|
SPE Production Operations Symposium, 10-12 March 1985, Oklahoma City, Oklahoma
|Copyright||Copyright 1985, Society of Petroleum Engineers|
A major consideration in fracture stimulation of the Bartlesville formation in Eastern Oklahoma is the lack of competent barriers to prevent downward fracture growth out of the oil-producing interval and into the water-producing interval. This has resulted in sizeable increases in water production with little or no effective stimulation of oil production with little or no effective stimulation of oil production. production. Attempts have been made to design stimulation treatments to minimize the downward fracture growth through the control of job size and pumping rates. This approach has produced some successful fracture treatments as will be discussed in this paper, but evidence indicates that in many cases proppant has been placed in the water-producing interval despite these measures.
This paper will present a different approach to minimizing water production resulting from hydraulic fracturing. It is based on the assumption that downward fracture growth cannot be sufficiently controlled using existing procedures. This approach will present the use of density controlled foam fracturing to selectively place proppants in the upper portion of the fracture adjacent to the oil-producing interval. Included are case histories of density control fracture treatments as well as those of conventional treatments performed in the Bartlesville. Also included are radioactive tracer surveys to support selective proppant placement using a density controlled foam fracturing proppant placement using a density controlled foam fracturing process. process
Thick sandstone formations often contain an oil-water contact which has been created by waterflooding or by a water drive reservoir. The Bartlesville sand in Cushing Field (Creek Co., Oklahoma), exhibits these characteristics. In some areas it contains a tight lime streak which separates the lower and upper sections and also functions as an effective vertical permeability barrier. However, this limestone is not areally continuous so it is only an isolated barrier to vertical permeability within the Bartlesville sand. Due to the sands depositional environment, the permeability decreases from the bottom to the top of the zone. permeability decreases from the bottom to the top of the zone. Consequently, the upper part of the formation is above the oil-water contact but is relatively tight and has low permeability. When hydraulic fracturing is used to stimulate the oil productive upper sand, the fracture will normally propagate downward into the water bearing zone. The resulting water production can be extremely high due to the permeability of the lower portion of the sand.
The Bartlesville sand has been the primary producing horizon for the Cushing Field which was discovered over 70 years ago. This zone has experienced a variety of secondary methods, most notably waterflooding, which have significantly altered the reservoir's fluid saturations. The Bartlesville sand in the Cushing Field has produced almost 200 MMBO since discovery in 1913. Waterflooding has contributed over 50 MMBO from this 110 foot section of sand. Water injection has preferentially entered the lower Bartlesville due to its high permeability relative to the upper Bartlesville (Fig. 1). The air permeability within the zone ranges from 60 md. at the top to 2 darcys at the bottom. The resistivity profile (Fig. 2) reveals the oil-water contact and the oil productive upper Bartlesville. The porosity within the formation is fairly uniform except for the porosity within the formation is fairly uniform except for the upper section, above the tight lime streak (Fig. 3). The porosity of the upper Bartlesville is 8% (porosity units) less than porosity of the upper Bartlesville is 8% (porosity units) less than the lower section. The upper portion is a shaly sand which must be hydraulically fractured to yield substantial oil production. Due to the lack of a competent barrier within the Bartlesville section, fractures tend to penetrate the lower Bartlesville. Consequently, the water production can be extremely high, sometimes exceeding 2000 BWPD for a stimulated Bartlesville producer. The oil production is not enhanced significantly due to the poor fracture production is not enhanced significantly due to the poor fracture propagation within the upper section. Obviously, the profitability propagation within the upper section. Obviously, the profitability of the stimulation treatment is questionable.
|File Size||843 KB||14|