Diagnostic and Analytical Technology of Pressure Transient Analysis for Horizontal Wells in Heterogeneous Reservoirs and Its Application

Most of carbonate reservoirs in Middle East are heterogeneous because of geological units and fluid properties such as high permeability zone (HPZ), faults, heavy oil and asphalt, which have a significant influence on streamline distribution inside the formation. In this condition, there are always rapid water breakthrough and invalid cycle of water for waterflooding patterns, leading to a poor sweep volume and oil recovery factor. For well pattern by horizontal injectors and producers, pressure transient analysis (PTA) is a practical tool to figure out reservoir permeability, wellbore contamination and effective horizontal length. These parameters are critical to analyze the distribution of remaining oil and then propose corresponding strategy to improve sweep efficiency. However, conventional PTA methods will not be applicable when HPZ exists. Numerical methods can solve this problem but it costs too much time to solve the partial differential equations discretely by unstructured grid so that it is difficult for massive PTA jobs for all wells of the reservoir. Therefore, our team proposed an improved method for pressure transient analysis and diagnosis. This technique is based on flow dynamics and mathematical method, which can describe the percolation flow for horizontal wells in the reservoir. Then, we build an equivalent homogeneous model and corresponding fitting algorithm for interpretation.