Experimental and simulation study on fracture conductivity of acid-fracturing in Dengying Formation of Sichuan Basin
Acid fracturing is a critical stimulation technology for enhancing production in ultra-deep marine carbonate reservoirs.A significant challenge in this process is maintaining the conductivity of acid-etched fractures under ultra-high temperature and high closure stress conditions.To address this,conductivity experiments were conducted using various acid solutions and their combinations.The morphology of the acid-etched fractures was captured using a three-dimensional laser scanner.The degree of fracture closure was analyzed using the Airy stress function and the complex variable method,integrated with the local cubic law and an acid fracturing model to create a numerical calculation method for evaluating the conductivity of acid-etched fractures.The results show that under high closure stress(90 MPa),the conductivity of acids and their combinations decreases by an order of magnitude compared to low closure stress(5 MPa).As closure stress increases,different acids and combinations exhibit distinct patterns of conductivity reduction,with potential for two rapid decline phases.Furthermore,specific acid combinations have been identified that enhance the conductivity of fractures under extreme conditions of temperature and pressure.The average error between the conductivity values calculated by the model and those obtained from experimental results is relatively low,about 10.6％,indicating that the model can effectively characterize the distribution and magnitude of conductivity across different points within the fracture.In Sichuan Basin,under identical engineering parameters,the conductivity of acid-etched fractures in the 4th member of Dengying Formation is higher than that in the 2nd member.This research provides valuable theoretical guidance for optimizing the design of acid fracturing stimulation schemes in ultra-deep marine carbonate rocks in Sichuan Basin.
NETL
NSTL
万方数据
