Conducting Multi-Stage Acid Hydraulic Fracturing in Carbonate Formations with Subsequent Intervals Production Efficiency Monitoring

Abstract

Abstract Tracer (marker)-based horizontal well studies are becoming increasingly common in the oil industry with the application of the innovative inflow indicators allowing production logging in horizontal wells along the well. This allows users to obtain analytical information for the effective management of production and field development processes. These technologies can significantly reduce costs and risks for oil and gas producing companies compared to conventional logging methods. The objective of the present study was to evaluate the production logging of horizontal wells stimulated with multi-stage acid fracturing. The monitoring technology was based on injecting marker dispersions into formation together with the acid stream during hydraulic fracturing. Acid-resistant monodisperse polymer microglobules, encoded for each of the stages using quantum dots and selectively interacting with water and oil, were used as marker inflow indicators. Acidic multi-stage fracturing was carried by utilizing a unique technology from "toe" to "heel" using a piercing perforator and CT with the injection of acid through the annular space. The separation of acid fracturing zones was carried out by the axial array packer. After the completion of stimulation works and after putting the well into operation, formation fluid sampling from the wellhead was carried out and analyzed to determine the number of tracers of each code. Based on the obtained analytical data, the formation fluid inflow profile along the horizontal well was built, allowing us to analyze the stimulation efficiency for each of the acid fracturing stages. Additionally, tasks such as the selection of the type and formulation of marker dispersions, their testing for compatibility with hydrochloric acid and hydraulic fracturing gel, working out the method for supplying tracers to the well and their placement in the formation, and evaluating the tracer particles adsorption degree in the rock were solved. Unlike conventional production logging in horizontal wells, the applied technology does not require special means of tool delivery and minimizes the risk of downhole tools getting stuck in the well and ambiguous data interpretation. It also does not require significant working costs. During the course of the work, the acid resistance and the physicochemical stability of the selected flow indicators in reservoir thermobaric conditions were confirmed. For the first time, production logging was conducted using the carbonate formation type and multi-stage acid fracturing, during which the inflow indicators were placed in eloxated acid fractures with long-term selective interaction of tracer particles with formation fluid. Based on the work results, geological and technical information was obtained for further planning of efficient geological and technical measures and additional oil recovery.