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Collaborating Authors
Results
SPE Members *Now retired Abstract A second successful surfactant flood pilot test was conducted by Exxon on the Lewis Ripley lease in a watered-out portion of the Weller sand, Loudon Field, Illinois. The salinity-tolarant, micellar/polymer process tested in this pilot incorporated several process modifications developed since a previous test was conducted in 1980. These changes included using a 25% smaller microemulsion bank size and addition of formaldehyde to injected fluids to inhibit bacterial degradation of biopolymer. The pilot was performed in a single, 0.71-acre [2873 m), 5-spot performed in a single, 0.71-acre [2873 m), 5-spot operated to approximate a confined pattern. Extensive data on flood performance were obtained from a comprehensive pilot monitoring program, including use of fluid tracers, observation wells, and post-test cores. Approximately 68% of the waterflood residual oil present in the test pattern was recovered. This present in the test pattern was recovered. This actually exceeded the oil recovery achieved in the first pilot, despite using a smaller microemulsion bank. Improved mobility control and lower surfactant retention contributed to enhancing process performance. Formaldehyde was effectively performance. Formaldehyde was effectively transported and prevented bacterial degradation of biopolymer. It appears to be an effective biocide for use in subsequent surfactant flooding operations at Loudon. During the pilot, an inexpensive and efficient method was developed to separate produced oil-water-surfactant emulsions. While produced oil-water-surfactant emulsions. While all test objectives were met, the effect of well spacing on oil recovery and chemical transport was not addressed. Introduction The Loudon field, operated by Exxon USA in Fayette County, Illinois, is, from a technical standpoint, a prime candidate for the application of microemulsion (surfactant) flooding technology. It is in an advanced stage of depletion after 13 years of primary production and 38 years of waterflooding. After completion of waterflooding, approximately half of the original-oil-in-place will remain unrecovered. Most of this oil is trapped by capillary forces in water-swept regions of the reservoir, where it is amenable to recovery by : surfactant process. One complicating factor, however, is the high formation brine salinity that contains 104,000 mg/L total dissolved solids TDS) with over 4000 mg/L divalent ions. The target reservoirs at Loudon are relatively shallow Mississipian (Chester) sandstones ranging in depth from 1400 to 1600 ft [427 to 488 m) sub. surface. The major oil-bearing sand, the Weiler, is a deltaic deposit consisting of fine- to very- fine-grained, well-cemented quartzose sandstones having good well-to-well continuity. in addition to the shallow depth and high-quality sands, average reservoir temperature -is a low 78 deg.F (25.6 deg.C] and the crude oil viscosity, at reservoir conditions, is 5 cp (5 mPa s]. Two papers have reported results from a successful field pilot test that evaluated salinity-tolerant surfactant flood process. The test, conducted by Exxon in 1980, involved a 0. 68acre [2752 m] 5-spot located on the Lewis Ripley lease (Fig. 1). It demonstrated the ability of the salinity-tolerant micellar/polymer technology to recover significant quantities of tertiary oil. During the test, problems were encountered with bacterial degradation of biopolymer and with separation of produced oil-brine emulsions. P. 463
- North America > United States > Illinois > Hamilton County (0.24)
- North America > United States > Illinois > Fayette County (0.24)
- Europe > United Kingdom > North Sea > Central North Sea (0.24)
- Geology > Sedimentary Geology > Depositional Environment > Transitional Environment > Deltaic Environment (0.54)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.44)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)
Control of Xanthan-Degrading Organisms in the Loudon Pilot: Approach, Methodology, and Results
Bragg, J.R. (Exxon Production Research Co.) | Maruca, S.D. (Exxon Production Research Co.) | Gale, W.W. (Exxon Production Research Co.) | Gall, L.S. (Exxon Production Research Co.) | Wernau, W.C. (Pfizer Inc.) | Beck, D. (Pfizer Inc.) | Goldman, I.M. (Pfizer Inc.) | Laskin, A.I. (Exxon Research and Engineering Co.) | Naslund, L.A. (Exxon Research and Engineering Co.)
Bragg, J.R.,* Maruca, S.D.,* Gale, W.W.,* and Gall, L.S., Exxon Production Research Co., Wernau, W.C., Beck, D., and Goldman, I.M., Pfizer Inc.; and Pfizer Inc.; and Laskin, A.I., and Naslund, L.A., Exxon Research and Engineering Co. *Members SPE-AIME Abstract An investigation of loss of mobility control in Exxon's Loudon micellar/polymer pilot test has confirmed that loss was caused by microbial degradation of the xanthan biopolymer used to viscosify the microemulsion and polymer drive banks. This paper describes techniques which were used to sample and culture bacteria from the Loudon pilot and demonstrate that these mixed cultures are able to degrade xanthan rapidly under reservoir conditions. Laboratory studies show that, under anaerobic conditions, bacteria cultured from the Loudon pilot can cause over 90% loss of xanthan viscosity in micellar/polymer fluids within seven days. To remedy this problem, an extensive laboratory screening program was conducted to identify biocides that are effective against the offending organisms. Complete kill of the organisms under repeated laboratory challenge tests was the chief screening criterion. Biocide compatibility (with biopolymer, formation rock, field brines, and microemulsion), cost effectiveness, and chemical stability were also judged key parameters for effectiveness in field applications. Of the biocides tested against the Loudon organisms, formaldehyde was found to be the most consistently effective, providing complete kill and persistence at levels of 500 to 2000 ppm. Formaldehyde persistence at levels of 500 to 2000 ppm. Formaldehyde was shown to reduce bacteria below detectable levels in the formation and permit propagation of xanthan in a follow-up test conducted within the highly contaminated pilot zone. Therefore, formaldehyde should be an effective biocide for future floods at Loudon. Introduction Two papers have reported details of a surfactant flood pilot test conducted by Exxon in the Loudon Field, Fayette County, Illinois. This pilot tested a micellar/polymer flooding process which recovers tertiary oil from high-salinity reservoirs without requiring a low-salinity brine preflush. The pilot was conducted in a 10 to 18 ft-thick sandstone pilot was conducted in a 10 to 18 ft-thick sandstone interval having a porosity of 19%, a permeability of about 150 md, and a reservoir temperature of 78 degrees F. The oil viscosity is 5 cp (5 mPa.s), and the brine salinity is approximately 104,000 ppm (mg/1) total dissolved solids (TDS), including over 4000 ppm of divalent ions (see Table 1). The pilot was conducted in a single, normal 5-spot pattern operated in a manner to approximate a confined 5-spot. Fig. 1 illustrates the pattern. In addition to four injectors and a central producer, the pattern contained five fiberglass-cased logging pattern contained five fiberglass-cased logging observation wells used to monitor changes in oil saturation during the flood. As described below, the observation wells were kept unperforated and filled with formation brine until late in the flood. After perforation they proved quite useful for sampling perforation they proved quite useful for sampling areal distributions of bacteria and polymer. While overall the test was highly successful, recovering 60% of the oil remaining in place after waterflood, loss of viscosity was observed as a major problem. Loss of viscosity was determined from two problem. Loss of viscosity was determined from two observations: a decline in polymer concentration at the producer past 0.75 PV production, and a marked decrease in pressure gradients between injectors and producer. Fig. 2 shows how loss of viscosity was producer. Fig. 2 shows how loss of viscosity was reflected in injectivity index (in BPD/psi, where psi is the difference between flowing bottomhole pressures in an injector and producer). After 0.65- pressures in an injector and producer). After 0.65- 0.70 PV of production (in November, 1981) the injectivity increased rapidly, returning to the original value within three months (injection rate was constant at about 0.12 PV/month). During March-April, 1981, after it was apparent that an irreversible loss of viscosity had occurred, the observation wells inside the pattern were perforated and sampled downhole for polymer and bacteria. perforated and sampled downhole for polymer and bacteria. Prior to perforation the formation brine in the Prior to perforation the formation brine in the wellbores was sampled downhole for bacteria and then swabbed out. This fluid showed no detectable bacteria under anaerobic and aerobic culturing conditions.
- North America > United States > Kansas > Butler County (0.24)
- North America > United States > Illinois > Fayette County (0.24)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.46)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)
Abstract A successful surfactant (microemulsion) flood pilot test in a watered-out portion of the Weiler pilot test in a watered-out portion of the Weiler sand, Loudon Field, Illinois (USA) was completed in October, 1981. The microemulsion system tested was designed to be effective in the presence of high-salinity formation water containing 104,000 ppm (mg/l) total dissolved solids (TDS) without use of a preflush. The test was conducted in a single, 0.68-acre preflush. The test was conducted in a single, 0.68-acre (2752 m2) 5-spot operated in a manner that approximated a confined pattern. The test was highly successful, recovering 60% of the oil remaining after waterflood. Cores from a post-flood well drilled within the pattern have confirmed the low final oil saturations and low surfactant retention achieved in the flood. Although oil recovery was excellent, loss of nobility control in the polyner drive bank and premature breakthrough of lower-salinity drive water premature breakthrough of lower-salinity drive water were observed part-way through the test. Laboratory and field studies conducted since flood termination have confirmed that loss was caused by bacterial degradation of the xanthan biopolymer used. Several biocides were tested in the laboratory and in a field injection experiment to determine their effectiveness against the bacteria contaminating the pilot. Formaldehyde was shown to kill bacteria within the formation, have negligible adsorption on reservoir rock, and permit propagation of undegraded polyner. Based on these test results, formaldehyde should protect xanthan biopolymer from bacterial degradation in future microemulsion floods at Loudon. Introduction Exxon is conducting a field pilot program to evaluate the potential of a microemulsion flooding process which can be used in high-salinity reservoirs process which can be used in high-salinity reservoirs without a brine preflush. Since the bulk of tertiary target oil amenable to surfactant flooding exists in reservoirs having brine salinities greater than 30,000 ppm (ng/l) TDS (defined here as "high salinity"), considerable incentive exists to develop such a process. Use of a preflush has certain disadvantages: flood life is extended, which increases operating costs; the preflush nay not contact all reservoir rock later contacted by lower-mobility micellar/polyner fluids, thereby reducing process performance; and large volumes of low-salinity water performance; and large volumes of low-salinity water nay not always be available for use in a preflush process. process. The pilot test was conducted in the Loudon Field, Fayette county, Illinois (USA). The reservoirs in this field are Mississippian Chester sandstones ranging in depth from 1400 to 1600 ft (427 to 488 n) subsurface. As shown in Table 1, the formation water contains about 104,000 ppm (ng/l) TDS including over 4000 ppm of divalent ions. Reservoir temperature is 78 deg. F (25.6 deg. C), oil viscosity is 5 cp (5 mPa s), and formation porosity averages about 19%. The Loudon reservoirs are in an advanced stage of depletion after 13 years of primary production and 31 years of water-flooding. It is estimated that at the economic limit of waterflooding slightly more than half of the OOIP will remain trapped as residual oil. Bragg et al. previously reported details of the pilot test, which was located on the Lewis Ripley pilot test, which was located on the Lewis Ripley lease in the Loudon Field (see Fig. 1). The test was conducted in a single, normal 5-spot pattern of 0.68 acres (2752 n2) operated in a manner to approximate a confined 5-spot. Fig. 2 shows the pilot well pattern at the reservoir sand depth of 1550 ft (472.4 n). In addition to the four injectors and central producer, the pattern contained five fiberglass-cased logging observation wells to allow use of induction and carbon/oxygen logs to monitor changes in oil saturation during the flood. The test was conducted in a small pattern to permit completing a field evaluation within a two-year permit completing a field evaluation within a two-year period and rapidly integrating results into an ongoing period and rapidly integrating results into an ongoing research program. P. 537
- North America > United States > Illinois > Fayette County (0.24)
- Europe > United Kingdom > North Sea > Central North Sea (0.24)
- North America > United States > Illinois > Hamilton County (0.24)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)
Members SPE-AIME The paper was presented at the SPE/DOE Third Joint Symposium on Enhanced Oil Recovery of the Society of Petroleum Engineers held in Tulsa, OK, April 4–7, 1982. The material is subject to correction by the author. Permission to copy is restricted to an abstract of not more than 300 words Write: 6200 N. Central Expwy., Dallas, TX 75206. Abstract A successful surfactant (microemulsion) flood pilot test has been completed by Exxon in a pilot test has been completed by Exxon in a watered-out portion of the Weiler sand, Loudon Field, Fayette County, Illinois. The microemulsion system tested was designed to be effective in the presence of high-salinity formation water containing 104,000 ppm (mg/l) total dissolved solids (TDS) without use of a pre-flush. The test was conducted in a single, 0.68-acre pre-flush. The test was conducted in a single, 0.68-acre 5-spot operated to approximate a confined pattern. Approximately 60 percent of the waterflood residual oil present in the pilot pattern was recovered. Extensive data for determining sweep and displacement efficiencies were obtained from observation well logs and fluid tracers. Although problems were encountered with bacterial degradation of biopolymer and with produced oil-water emulsions, the test is considered to be a technical success and confirms the effectiveness of the high-salinity microemulsion formulation. Additional pilot tests are needed to determine the effects on oil recovery of microemulsion bank size and well spacing. Introduction The Loudon Field, operated by Exxon Company, USA in Fayette County, Illinois, represents a challenging tertiary recovery target. It is in an advanced stage of depletion after about 13 years of primary production and 30 years of waterflooding. After production and 30 years of waterflooding. After waterflooding is completed, almost half of the OOIP will likely remain unrecovered. The Loudon reservoirs are Mississippian Chester sandstones ranging in depth from 1400 to 1600 feet subsurface. The depositional environment in the pilot area is generally deltaic with stream-mouth bars and delta fronts containing fine-to-medium grain, well-cemented sands having good well-to-well continuity. Reservoir temperature is 78 deg. F, oil viscosity is 5 cp, and the formation water contains about 104,000 ppm (mg/l) total dissolved solids (TDS) including over 4000 ppm of divalent ions (see Table 1). An earlier surfactant flood pilot conducted at Loudon in 1969 used a large-volume; low salinity preflush prior to injection of a petroleum sulfonate preflush prior to injection of a petroleum sulfonate surfactant system that was only effective at low salinity. The main conclusion reached from that test, which recovered only about 15% of the residual oil in the test area, was that preflushes are likely to be ineffective unless the surfactant system has a broad salinity tolerance. Much of the surfactant flooding research conducted subsequently by Exxon Production Research Company has been directed toward Production Research Company has been directed toward developing microemulsion systems that are effective in high-salinity reservoirs without requiring a preflush. The test reported here used this type of preflush. The test reported here used this type of microemulsion formulation. As shown in Fig. 1, the test was conducted in the southern end of the Loudon Field on the 80-acre L. Ripley lease. A single, normal 5-spot pattern of 0.68-acre area was operated to simulate a confined 5-spot. Bottomhole well locations within the test sand at a depth of 1550 feet are shown in Fig. 2. Five fiberglass-cased logging observation wells were included within the pattern to allow use of both induction and carbon/oxygen logs to monitor changes in oil saturation and salinity during the flood. Extensive use was made of observation well logs, fluid tracers, and injection flow surveys to determine both vertical and areal sweep. An objective was to obtain data on bank velocities and displacement efficiencies in various strata and pattern quadrants that would aid in correlating pilot performance with laboratory core floods. Although a small pattern was chosen primarily to permit a rapid process evaluation, the resulting close well spacings also allowed an extremely detailed reservoir description which will facilitate test interpretation. Pilot wells were drilled and completed in 1977, surface facilities were installed in 1979, and microemulsion injection was initiated on May 13, 1980. The flood was ended on October 16, 1981 after 2.25 PV total fluid production; however, post-flood PV total fluid production; however, post-flood evaluation tests are still in progress. Detailed test interpretation, including modeling of the pilot with a chemical flood simulator, is currently being conducted. P. 933
- North America > United States > Illinois > Fayette County (0.44)
- North America > United States > Texas > Dallas County > Dallas (0.24)
- North America > United States > Oklahoma > Tulsa County > Tulsa (0.24)
- Geology > Sedimentary Geology > Depositional Environment (0.54)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.34)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)