Measurement of Molecular Weight Distribution of Polyacrylamides in Core Effluents

He, Qin-gong; Young, T. S.; Willhite, G.P.; Green, Don W.

doi:10.2118/17343-pa

Cited by 12 publications

(8 citation statements)

References 8 publications

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“…Along with this increase in polymer retention, resistance factors and residual resistance factors increased by factors from 13 to 20. Hirasaki and Pope (1974) noted HPAM (Dow Pusher 700) retention in sandstone was twice as high in an 80-md core as in a 359-md core.…”

Section: Literature Review Of Factors Affecting Polymer Retentionmentioning

confidence: 90%

Field vs. Laboratory Polymer-Retention Values for a Polymer Flood in the Tambaredjo Field

Manichand

Seright

2014

SPE Reservoir Evaluation &Amp; Engineering

127

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During a polymer flood, polymer retention can have a major impact on the rate of polymer propagation through a reservoir, and consequently on oil recovery. A review of the polymer-retention literature revealed that iron and high-surface-area minerals (e.g., clays) dominate polymer-retention measurements in permeable rock and sand (>100 md). A review of the literature on inaccessible pore volume (IAPV) revealed inconsistent and unexplained behavior. A conservative approach to design of a polymer flood in high-permeability (>1 darcy) sands would assume that IAPV is zero. Laboratory measurements using fluids and sands associated with the Sarah Maria polymer flood in Suriname suggested polymer retention and IAPV values near zero [0620 lg/g for retention and 0610% pore volume (PV) for IAPV]. A procedure was developed using salinity-tracer and polymer concentrations from production wells to estimate polymer retention during the Sarah Maria polymer flood in the Tambaredjo reservoir. Field calculations indicated much higher polymer-retention values than those from laboratory tests, typically ranging from approximately 50 to 250 lg/g. Field cores necessarily represent an extremely small fraction of the reservoir. Because of the importance of polymer retention, there is considerable value in deriving polymer retention from field results, so that information can be used in the design of project expansions.

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Section: Literature Review Of Factors Affecting Polymer Retentionmentioning

confidence: 90%

Field vs. Laboratory Polymer-Retention Values for a Polymer Flood in the Tambaredjo Field

Manichand

Seright

2014

SPE Reservoir Evaluation &Amp; Engineering

127

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“…Sorbie 1991). The molecular weight distribution was shown to be modified by mechanical degradation (He et al 1990). To measure the molecular weight distribution, SEC can be used.…”

Section: Molecular Weight Distribution Measurement Using Size Exclusimentioning

confidence: 99%

“…The molecular size distribution can be measured using Size Exclusion Chromatography (SEC) or Low-Angle-Light Scattering (e.g. Gregory 1984, Hunt et al 1988, He et al 1990.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Degradation of Polymers During Injection, Reservoir Propagation and Production - Field Test Results 8 TH Reservoir, Austria

Puls

Clemens

Sledz³

et al. 2016

SPE Europec Featured at 78th EAGE Conference and Exhibition

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The polymer pilot test performed in the 8 TH sandstone reservoir in Austria shows incremental oil production. Soon after increasing oil cuts were detected, polymer was back-produced from the wells which were showing the oil production response. The polymer concentration increased to about 100 ppm in the back-produced water.Size Exclusion Chromatography was used to determine the molecular weight distribution of the back-produced high molecular weight polymers (HPAM). The results showed that careful sampling is required to avoid degradation of polymers during the sampling procedure. Analyzing pressurized samples revealed that some degradation of polymers from the original average molecular weight of 20 MDa to 8 MDa occurred.To investigate where in the surface facility-injection-reservoir-production system degradation took place, specific field tests and laboratory experiments were performed.Chemical and biological degradation was excluded as reservoir conditions are benign (50°C, 20,000 ppm) and nitrogen blanketing and biocides are used.At the surface facilities, no degradation was detected. Swabbing and laboratory experiments showed that severe mechanical degradation occurs in injection wells if injection is performed under matrix injection conditions owing to high flow velocities in the near-wellbore. However, induces fractures are substantially decreasing mechanical degradation. To avoid severe degradation of HPAM, the flow velocities in the near-wellbore and related mechanical degradation have to be evaluated and the injection designed accordingly.In the reservoir, polymers are not degraded as the flow velocities are low. Sucker Rod Pumps as used in the production wells in the polymer pilot area do not lead to polymer degradation. This means surface polymer samples can be taken to investigate the degradation in the injection well.Surface sampling has to be performed pressurized to avoid high shear rates and oxygen in the samples.

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“…The measurement of molecular weight (MW) distribution of high MW partially-hydrolyzed polyacrylamides (HPAMs) is prohibitively difficult for routine screening studies (Hunt et al, 1986;He et al, 1988;Lecourtier et al, 1984;Langhorst et al, 1986). Nevertheless, knowledge of the MW distribution of HPAMs can inform molecular weight optimization for lowpermeability formations.…”

Section: Polymer Molecular Weight Optimizationmentioning

confidence: 99%

Overcoming Design Challenges of Chemical EOR in High-Temperature, High Salinity Carbonates

Levitt

Klimenko

Jouenne

et al. 2013

SPE Middle East Oil and Gas Show and Conference

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The optimization of chemical floods for a low-permeability, high-salinity, high-temperature carbonate formation presents several unique design challenges, which may be overlooked in short coreflood experiments. Low permeability formations require the optimization of polymer molecular weight distribution such that both mobility reduction and injectivity are maximized. The effects of high core-scale heterogeneity must be understood and mitigated, for example, by increasing core length. These subjects are explored in the context of an ongoing flood design project. Understanding and mitigation of pressure build-up issues -possibly related to high surfactant adsorption -is an ongoing challenge. Additionally, an attempt will be made to shed light on the discrepancy between available carbonate capillary desaturation curves for carbonates and the near-complete recovery reported in surfactant-polymer corefloods. Effect of dispersivity on chemical floodsGash and Griffith (1980) suggest that, for rocks with low dispersivity, such as Berea, cores as short as 30 cm may yield high recovery in laboratory chemical floods. Clastic reservoirs often contain high-correlation length heterogeneities (e.g. stratification), which, when averaged across an entire section, may add a length scale-dependent megascopic component to dispersion measurements (Arya et al., 1988;Gelhar et al., 1992;Barth et al., 2001). Thus, Arya et al. (1988) differentiate between megascopic dispersivity, which controls volumetric sweep efficiency, and macroscopic dispersivity which determines real mixing in porous media and is under interest of miscible EOR. The ratio of mean correlation length of permeability field to mean distance travelled is proposed as a factor of nature of mixing: if this ratio is much less than one, dispersivity represents true mixing, and is proportional to the mean correlation length. In the opposite case, measured dispersivity results from megascopic heterogeneity as well as dispersion. The criteria α/L<<1 can thus be applied to determine whether the nature of dispersion measurements is truly mixing, or rather an artifact due to large scale heterogeneity. Too much of either can be detrimental to chemical flood performance, the former yielding dilution of the surfactant slug, the latter yielding poor sweep.

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Measurement of Molecular Weight Distribution of Polyacrylamides in Core Effluents

Cited by 12 publications

References 8 publications

Field vs. Laboratory Polymer-Retention Values for a Polymer Flood in the Tambaredjo Field

Field vs. Laboratory Polymer-Retention Values for a Polymer Flood in the Tambaredjo Field

Mechanical Degradation of Polymers During Injection, Reservoir Propagation and Production - Field Test Results 8 TH Reservoir, Austria

Overcoming Design Challenges of Chemical EOR in High-Temperature, High Salinity Carbonates

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