Flowback Analysis Methodologies and Precipitation Risk During Siderite-Bearing Carbonate Acidizing
Abstract Acidizing is the most commonly used method to stimulate carbonate reservoirs. To achieve a better assessment of the operation, a flowback analysis is conducted. Flowback analysis can give insights on the reservoir's response to the recipe. This analysis can be used to improve future treatment operations where some recommendations were deduced. The objective of this paper was to show the flowback analysis methodology following carbonate acidizing treatments with a focus on dissolved elements. X-ray diffraction (XRD), X-ray fluorescence (XRF), environmental scanning electron microscope (ESEM), and inductive coupled plasma (ICP) were used to determine the composition of flowback fluids and the filtered precipitate. Combining the data from different techniques onsite and in laboratory assess the development of a methodology for calculating more accurate amounts of dissolved elements, formation water, and volumes of recovered fluids. This analysis showed acid recipes efficiency of nearly 100% based dissolved calcite. Around 65% of injected fluids were lost into a formation. The iron concentration during the flowback was 1400 ppm, however, cumulative amount of iron in flow back samples was below expected value. Based on the formation's rock analysis, the theoretical amount of iron in the recovered flowback fluid was 1000 kg. The measured amount of iron was 500 kg and the rest could be assumed to be precipitated in a reservoir. This study helps in understanding the flowback fluid analysis and its importance by using a step-by-step analysis procedure for flowback fluid samples from the carbonate acidizing operations. The results of this study help in tracking the elements that potentially help in estimating the lost fluids volumes and percentage of success for a carbonate reservoir acid operation.