A tertiary recovery pilot of a low-tension waterflood process was conducted in the Salem Unit. A 5-acre, five-spot pilot was installed inside a previously waterflooded 20-acre, five-spot pattern in the Benoist reservoir previously waterflooded 20-acre, five-spot pattern in the Benoist reservoir to provide afield test of a chemical flooding process found successful in laboratory experiments. Introduction A tertiary chemical process for recovery of oil remaining after conventional waterflooding has been pilot tested in the Benoist sand reservoir of the Salem field, Marion County, Ill. The pilot was applied in a 5-acre five-spot pattern that consisted of four injection wells, two pattern that consisted of four injection wells, two observation wells with bottom-hole locations 67 and 164 ft from one of the injectors, and a center producer. This was a joint Texaco Inc./Mobil Oil Corp. test, slice the low-tension waterflood process is under license from Mobil, which is a co-owner in the Salem Unit. Four separate injection phases comprised the process: process: Phase 1. A 0.5-PV, three-part, aqueous reservoirconditioning slug consisting of (1) 0.2 PV of softened fresh water to initiate displacement of formation brine, (2) 0.1 PV of fresh water containing 6,000 ppm sodium carbonate to reduce, through precipitation, undisplaced divalent ions, and (3) 0.2 PV of fresh water containing 6,000 ppm sodium carbonate, 1,000 ppm sodium tripolyphosphate to reduce further the divalent ion concentration, and 6,000 ppm salt (NaCl) to maintain the desired level of salt concentration for optimum surfactant reaction. Phase 2. A 0.285-PV surfactant slug composed of 20,000 ppm of petroleum sulfonate mixed in softened fresh water containing 6,000 ppm each of sodium carbonate and sodium chloride and 1,000 ppm of sodium tripolyphosphate. Phase 3. A 0.3-PV, two-part polymer drive slug:0.1 PV of 700 ppm biopolymer hydrated in salinity-adjusted, fresh and softened water, and0.2 PV of biopolymer-thickened water, as above, with polymer concentration reduced gradually from 700 to 0 ppm. Phase 4. 1.0 PV of Salem field injection brine to provide the final drive. provide the final drive. The desired injection rates into all chemical injectors were maintained over the life of the pilot test, with the exception of a 40-day period of reduced injection during the surfactant phase caused by an interruption in sulfonate supply. However, all chemical injectors were treated selectively twice to improve vertical distribution of injected fluids. It was also necessary to acidize the center producer, Well 5-2, on two occasions to maintain total producer, Well 5-2, on two occasions to maintain total fluid withdrawal. Location The Lake Centralia-Salem pool is located between the cities of Salem and Centralia in Marion County, Ill., about 70 miles east of St. Louis (Fig. 1). The field contains 8,800 surface acres and is 6 1/2 miles long and 2 1/2 miles wide. The field was discovered in 1938 by Texaco Inc. and 2,400 wells have been drilled. Eight horizons have produced under primary conditions and four have been subjected to full-scale waterflooding operations. The field was unitized for waterflooding on Sept. 1, 1950, with Texaco as unit operator (Fig. 2). Geology JPT P. 925
The Texaco operated surfactant-polymer project at the Salem Unit, Marion County, Illinois contains twelve patterns totaling sixty acres. A brine tolerant surfactant formulation, requiring no formation preconditioning, was injected into the watered out Benoist Sandstone and followed with a biopolymer. Different tracers were injected with the surfactant at the various injection wells. From the produced tracer concentrations, the relative distribution of surfactant in all 48 pattern quadrants was determined. pattern quadrants was determined. Initial production rates were higher than planned and resulted in uneven surfactant planned and resulted in uneven surfactant distribution. Further flow distortion occurred due to uneven pressure build-up at the surrounding backup injection wells. Log interpretation, etc. indicated that the top third of the Benoist Sand had not been completely waterflooded. Thus, it was not unexpected when most of the chemical flood entered the lower two-thirds of the reservoir. Interpretation of logs run in monitor wells indicated that oil saturation was reduced to 2–8% in some intervals. Analyses of periodic samples from adjacent monitor wells revealed component changes as the surfactant moved from injectors to producers. producers. Pressure changes during polymer injection and produced liquid analyses from monitor wells produced liquid analyses from monitor wells indicated an early loss of polymer effectiveness attributed to bacterial degradation. The resultant waterflood type displacement mechanism substantially slowed the mobilized oil displacement and recovery rate. However, current projections of ultimate tertiary oil recovery are approximately 47% of the oil-in-place in the total Benoist Sand. Assuming that all of the oil was produced from the lower interval, the recovery efficiency will be 76%. These recoveries illustrate the capability of the brine tolerant surfactant system. It is also apparent that positive means for maintenance of polymer viscosity and chemical placement must be polymer viscosity and chemical placement must be employed. Introduction The design and implementation of the Salem Unit Surfactant/Polymer Project was described in 1983. In review, the Salem Unit is located in South Central Illinois about 70 miles (113 km) east of St. Louis, Missouri. Figure 1 shows the project site location. The subject chemical flood was conducted at 1750 ft (533 m) in the waterflood depleted Benoist Sand. The project configuration and well layout are shown in Figure 2. Twelve 5-acre (2 ha) elongated, inverted five-spot patterns comprised the designated 60-acre (24.3 ha) chemical flood area. It is noted that there are two totally enclosed interior patterns. For ease and identification, each pattern is numbered the same as its injection well. There are a total of 12 chemical injection wells and 20 producing wells. A total of 24 surrounding backup injection wells were used to confine the chemical flood to the designated area. Injection rates of the backup injection wells on the immediate east and west sides of the project area were scheduled so that, theoretically, there would be a no flow zone between the inner and outer rows of backup injection wells on those sides. The total area associated with this effort was about 200 acres (81 ha).
Texaco, as operator of the Salem Unit, Marion County, Illinois, is conducting a 60 acre semi-commercial tertiary recovery project in the watered out Benoist sandstone. This paper discusses field design and implementation of the project as well as results to date. An extensive field testing program preceeded initial injection. The process used is the Texaco developed brine tolerant surfactant system followed by a biopolymer. Application of this process field-wide in the Benoist reservoir at Salem is anticipated to have a tertiary oil target of 50 million barrels. The project demonstrates a process which extends greatly the reservoir salinity range for which surfactant systems have application. The surfactant system was successful in mobilizing waterflood residual oil. More importantly, the project demonstrates the capability of designing surfactant systems for use in high brine reservoirs without expensive time consuming pre-flushing or reservoir pre-treatment. Field results indicate problem areas to be: Contacting the reservoir with injected fluids (Volumetric Sweep Efficiency), handling and mixing of viscous injectants, treating produced emulsions, obtaining accurate well tests, and bacteria control in biopolymer solutions.
seotis tumour appeared, and the whole limb from a little above the ankle to the knee, was daily increasing in size. A hard tumour was discovered in the ham,, and the patient began to manifest symptoms of hectic. Conceiving amputation to be indispensable, I performed the operation above the knee, assisted by Drs. Otis, Bayley and Callimore. On examination, the tibia and fibula were found to be united into one solid substance, the bones exhibited no marks of necrosis or caries, but were enlarged to about thrice their natural size ; being sawed transversely about midway between the knee and ankle, (he bony substance measured on its longest diameter 4 inches. The tumour in the ham being dissected out, was found to be a complete bone, or osseous substance, about three inches long and two inches broad, entirely disconnected with the femur. Un-
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.
customersupport@researchsolutions.com
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.