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Experimental Evaluation of Fouling Processes in Porous Polyethylene Well Screens Used for Horizontal Wells
Author(s) -
Logan Andrew J.,
Siegrist Robert L.,
MunakataMars Junko
Publication year - 2002
Publication title -
groundwater monitoring and remediation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 47
eISSN - 1745-6592
pISSN - 1069-3629
DOI - 10.1111/j.1745-6592.2002.tb00658.x
Subject(s) - effluent , materials science , porosity , scanning electron microscope , polyethylene , saturation (graph theory) , porous medium , hydraulic head , fouling , composite material , chemistry , environmental engineering , environmental science , membrane , geotechnical engineering , geology , mathematics , combinatorics , biochemistry
The hydraulic performance of porous polyethylene well screens was examined in laboratory columns to understand the processes that affect well performance in many field applications. Conditions studied included (1) well‐screen pore size; (2) the presence of biodegradable drilling fluid, biological electron acceptors, and biofouling organisms; and (3) chlorine development. Custom‐fabricated, segmentable acrylic columns (8.9 cm diameter. 64 cm length) were employed using a factorial design statistical approach to mimic a variety of representative field conditions experienced during field applications. After circular well‐screen coupons (circular sections of the well screen cut to match the diameter of the columns) were cut and secured horizontally in the columns, sand media, and, in some cases, biodegradable drilling fluid were packed on top of the well screens. Those columns receiving chlorine development were allowed to sit overnight after a 1000 ppm chlorine solution was introduced beneath the well screen following upflow saturation. The columns were upflow saturated and then operated with simulated ground water in a down flow mode under constant hydraulic head for up to 75 days. Residual head with depth was measured and flux density values were recorded over time. Effluent samples were collected and analyzed for dissolved oxygen (D.O.), electrical conductance, pH, and total solids. After achieving pseudo‐steady‐state throughput condition as indicated by relatively constant effluent flux densities, the columns were dismantled and the well‐screen coupons were examined under a scanning electron microscope to observe causes of any loss in flow observed. The hydraulic conductivities of the well screens were also measured before and after operation in the columns. Results show that these porous polyethylene well screens resist fouling due to microbial colonization or chemical precipitation. Scanning electron microscopy revealed little or no colonization of the surfaces by microbes or blockage of pores by particle entrapment. Hydraulic head measurements revealed that the cause of headloss in the columns was a result of processes that occurred in the overlying sand media and not within the well screens themselves.