A New Method to Determine and Forecast Deliverability Equation for Fractured Horizontal Well in Tight Gas Reservoir

摘要

For fractured horizontal well under depletion mode, average formation pressure would decease as a result of gas producing. Pressure-dependent parameters, including fluid properties, reservoir permeability, fracture conductivity and high-velocity non-Darcy flow coefficient can lead to the change of deliverability equation. The objective of this paper is proposing a new method, which is easy to conduct, to determine deliverability equation and quantify the change rule. The method in this paper involves production data analysis and numerical simulation. Specifically, daily Production data are divided into several segments first. Second, production data analysis method, including straight-line, type curve and history match method, are conducted to obtain formation and fracture parameters for each segment, based on which, pressure-dependencies are quantified. Finally, by constructing numerical simulation model, deliverability equation for different time could be determined or forecasted with simulated modified isochronal well test. The methods in this paper are validated by field data from Sulige tight gas field. The results show that the pressure-dependence coefficients obtained by Segment-PDA (Production Data Analysis) method is similar to the laboratory findings, while deliverability equation determined by simulated modified isochronal well test method is almost the same with actual productivity testing results. With confidence, the procedures in this paper are applied to 169 vertical wells and 73 horizontal wells in Sulige gas field. We find that the reservoir permeability and fracture conductivity is quite stress-sensitive in this tight gas field and the deliverability equation changes differently from the condition that ignoring pressure-dependencies. It is hoped that the method in this paper could be an easy and accurate way to determine and forecast deliverability for fractured horizontal well in tight gas reservoir.