1 Use of Oxidizing Chemistry in Addressing Microbial Challenges in conventional Oil & Gas Production Rob Ryther, Ph.D. Production & Water Management March 26, 2013
Agenda Addressing Microbial Challenges in Unconventional Oil Production with Peracetic Acid Impact on completions Impact on production Impact on disposal
Microbial Challenges Well/reservoir souring Organisms use sulfur species and produce H2S HSE issue, devaluation of oil/gas, corrosion issues Microbiologically-influenced corrosion (MIC) Asset integrity challenges Production of biofilm on the tubing/top-side equipment Bio-fouling Biofilm build-up/plug membranes and filters Can lead to production down time for cleaning Gel fluid stability Microbes can destabilize gel fluids by consumption of guar
Water Crosses All Operator Boundaries Drilling Completions Production Life-long Microbial Control Identify risk areas and define mitigation strategy Key is communication between all 3 steps
BIOCIDE TREATMENTS FOR HYDRAULIC FRACTURING APPLICATIONS VOC: Need a treatment strategy that: Minimizes microbial risks Is cost effective Has a good environmental profile Allows water clean-up/ reuse
GENERAL GUIDELINES FOR BIOCIDE SELECTION DURING FRACTURING APPLICATIONS Microbial kill performance Cost Frequency of dosage Materials Compatibility Compatibility with downstream processes (fracturing gel formation, etc) Environmental impact Operation Safety Oxidizing versus non-oxidizing
COMPARISON BETWEEN OXIDIZER AND NON-OXIDIZING BIOCIDES Criteria Non-Oxidizing Oxidizing Performance Good Good Speed of kill Hours Minutes Persistence Medium/High Low Environmental footprint (Bioaccumulation) Medium/High Low/Medium Use in closed systems Yes No Corrosivity Low/Medium Medium/High
8 Microbial Impact on Completions
Water Quality Challenges Water can sit stagnant for long periods because of large quantities needed Optimal opportunity for microbial growth, solids drop out, and biofilm proliferation Must decided where to treat the water: At holding site At well location Before Treatment After Treatment Trade-off is increased contact time (better biocide performance) versus moving biocide treated water
Risk Model for Minimizing Microbial Risks Total microbes per ml 10 e10 10 e8 10 e6 10 e4 10 e2 Risk Tolerance Biocide Biocide Uncontrolled microbial growth Max Target 10 e0 0 Risk Tolerance Pit Transfer to site On-site tanks Completion Microbial-based product fouling begins to occur as growth develops uncontrollably (H 2 S and corrosion)
CHEMICAL PERFORMANCE IN THE FIELD
On-the-fly Microbial Control Control with only onthe-fly treatment is difficult Biocide selection is critical Short contact time Fast acting product Pre-treatment makes on-the-fly control much more manageable Log Reduction 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 1.15 4.05 4.11 3.74 2.05 2.11 1.87 1.74 1.76 25 150 300 Dosage 15 minutes contact time
13 Microbial Impact on Production
Control vs. Sterilization Cannot economically sterilize all water sources Minimize microbes Monitor growth and activity Understand where microbes are coming from Microbes introduced in drilling and completions Microbes endogenous to the reservoir Challenging to detect by culture-based methods Can cause problems such as MIC and H 2 S generation
Microbial Counts ATP method LOCATION Untreated Flowback water Treated Battery Fresh Water Working Tanks 4 DAYS 8 DAYS 1 MONTH 2 MONTHS 3 MONTHS 4 MONTHS Average ME/mL 7,999,511 148,005 966,875 1,319,113 159,486 241,494 133,321 108,252 49,396 73,737 Microbes/mL 9,000,000 8,000,000 7,000,000 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000,000 0 Untreated Battery Treated Battery Peracetic Acid Treatment Fresh Water Working Tanks H2S (ppm) Microbes/mL 4 DAYS 8 DAYS 1 MONTH 2 MONTHS 3 MONTHS 4 MONTHS 18 16 14 12 10 8 6 4 2 0 H2 S (ppm) LOCATION Untreated Flowback water Treated Battery Fresh Water IRON -- PPM Working Tanks 4 DAY 8 DAY 1 MONTH 2 MONTHS 3 MONTHS AVERAGE 19.1 0.9 0.0 0.7 12.1 11.8 39.5 113.5 118.3 Iron (ppm) 140 120 100 80 60 40 20 0 Untreated Battery Treated Battery Fresh Water Working Tanks 4 DAY 8 DAY 1 MONTH 2 MONTHS 3 MONTHS
Archaea in Shale Gas Production Archaea are endogenous to many reservoirs Can be stimulated during completion Example from the Fayetteville shown below Microbes identified by qpcr Enumeration by DNA-based technology Provides insight into Archaea risks Fresh water sources (pond and creek) Archaea per ml <LOD Risk Low Produced water sample #1 115,000,000 High Produced water sample #2 180,000,000 High
Monitoring Risk for the Life of the Well Potential risk for microbial challenges during the life of the well Monitoring is key Microbial numbers/species/activity Field KPI Proactive feedback is critical for control Options for regaining control Control microbial risks from drilling through production Biocide down the back side of the well Biocide squeeze/soak
18 Microbial Impact on Water Disposal Well
Peracetic Acid Biocide and FeS/H2S Removal Rapid bacterial kill Iron sulfide oxidation to iron sulfate H 2 S removal Provides opportunity for recycling or optimized disposal for high iron sulfide/h 2 S containing waters for
Peracetic Acid Biocide and FeS/H2S Removal Combining PAA biocidal activity and FeS/H2S oxidation (solid formation) with conventional water clarification programs Enhances solids formation achieved by PAA Increases actual biocidal activity by removing sessile bacteria with solids Requires effective solids removal and processing program Multiple options can be used to developed optimized program
PAA Rehabilitation of SW Disposal Well 1000 PPM PAA @ 10:45 AM Colonies/mL Day 1 Significantly decreased bacteria levels in FWKO Cleaning released sessile biomass from facility Day 2 Conc Increase removed new level of biofilm/ FeS residual in FWKO Trend follows more rapidly down stream in large volume water transfer tanks Colonies/mL 1000 PPM PAA @ 8:30 AM 1500 PPM PAA @ 9:30 AM
Summary Microbial control throughout the process is critical Lack of control up-front can result in microbial challenges for the life of the well Biocides selection and application can make a significant impact on the success or failure of a treatment program A best-in-class control strategy: Takes into account when and where the microbes are introduced Controls microbes throughout the process Minimizes risk of downstream microbial issues Examples shown of biocide/clarification program demonstrated to have broad biocidal applications for unconventional oil & gas water treatment
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