Michelle C. Flippen & B. Helena Yang, CJ Services
The removal of polymers utilized in oilfield applications is important to the conductivity and productivity of a well. Unbroken gel residue and dynamically formed filter cake on the formation faces are two forms of damage resulting from drilling, fracturing, gravel packing and workover operations. Monitoring the extent of polymeric damage and its cleanup through removal treatments is best achieved through the analysis of flowback samples. This form of analysis can provide valuable information regarding polymer degradation downhole and be used as a quantitative profile for the amount of treatment load recovered. Flowback samples can be tested before and after treatments to determine the total carbohydrate content, which is a measurement of sugar concentration, in pounds per thousand gallons. Guar, cellulose, starch, xanthan and other polysaccharides used as viscosifling agents are examples of complex sugars. Although high carbohydrate levels are a symptom of damaged wells, it is misleading to conclude that lower carbohydrate content equates to a lesser degree of damage. Other factors, such as bacterial presence, breaker activity and size distribution of polymer fragments, contribute significantly to the results of a flowback analysis. This paper presents an improved method to effectively analyze flowback samples. Laboratory protocols are provided and include tests for carbohydrate content, molecular weight distribution, enzyme/bacteria detection and viscosity measurements. This improved flowback analysis provides a method to evaluate polymer load recovery and to detect any polymer damage downhole. Several field studies are also included to demonstrate this comprehensive analytical procedure and how it supplies a more conclusive posttreatment evaluation.