Quantifying Guar Polymer Recovery Post Hydraulic Fracturing to Determine the Degree of Fracture Cleanup: A Field Study of the Point of Rocks Formation, California

Abstract A field study was initiated to determine fracture cleanup by examining the carbohydrate content of flowback water production from a series of hydraulic fracture stages in the McKittrick field Point of Rocks formation. The study was an effort to understand hydraulic fracture cleanup of the Point of Rocks formation and obtain an idea on the amount of fracture volume contributing to production to optimize hydraulic fracturing design. The carbohydrate content and concentration measured from the water flowback samples are used as direct estimation to the amount of guar polymer recovered post-fracturing treatments. Carbohydrate estimation via anthrone testing method to quantify load recovery is by far the most accurate water analysis method available to the industry outside of injecting (and recovering) any special chemical markers. By contrast, studying the ionic content of produced waters by itself can be a misleading quantifier to load recovery due to the mixing and dilution of the pumped frac water with produced formation water. However, the accuracy of polymer quantification using the anthrone method is as accurate as the process of sampling, the frequency of sampling, the time from sampling to testing, the sample container, the testing method, and the calculations involved due to sampling frequency. This paper will discuss the anthrone testing method and will share guidelines that will enhance the accuracy of the testing process. The paper will also compare the guar polymer recovered from a number of hydraulic fracture stages in different Point of Rocks sands and compare to the amount of polymer pumped to present "hypothesis" as to the percent of the propped fracture actually contributing to production.