Lessons Learned from Bacteria Monitoring and Treatment in Marcellus Production Operations

摘要

Significant effort around bacteria monitoring has been a focus since July 2016.Water testing program covers all operating areas including southwestern Pennsylvania and Marshall county,West Virginia.The program began with most probable number(MPN); otherwise known as serial dilution testing,for sulfate reducing bacteria(SRB)and acid producing bacteria(APB).Based on the water test results,biocide treatments were performed for selected wells from October 2016.More than 300 horizontal wells from Marcellus formation were tested for SRB and APB by third quarter 2017 and biocide treatments were optimized by the end of 2017.Bacteria DNA testing in the form of next generation sequencing(NGS)and quantitative polymerase chain reaction(qPCR)was performed on selected wells to characterize the microbial consortium present in these samples.Due to the limitations of serial dilution testing and understanding of the bacteria makeup with DNA testing,the program has evolved to utilize fieldwide adenosine triphosphate(ATP)testing and a locked-down biocide treatment procedure.Biocide treatments are prioritized during extended midstream maintenance to minimize downtime and maximize contact time and have shown to be effective for extended durations.To investigate the root causes of bacteria,data science tools are utilized to look at the effect of the completions design and other variables on bacteria during operation.Variables under consideration include biocide type and concentration,fracturing fluid chemical additives,produced water reuse during completions,produced water chemistry,and geologic variation.Initial findings will be discussed and shared with lessons learned from production operations.