Formulizing relationships between producing area of fracture-controlled unit and productivity of segmented multi-cluster fractured well by delineating water saturation limit

Abstract

Predicting the producing area of fracture-controlled unit created by hydraulic fracturing is crucial to fracturing evaluation, estimation of remaining reserves and formulation of development plan. Under the background of segmented multi-cluster fractured horizontal wells intercepted by line-shaped fractures, this study establishes a transient gas-water two-phase flow model to solve the analytical solutions of gas-water productivity, formation pressure and water saturation in water-bearing shale gas reservoirs, well matching with the field production data and simulation results. Subsequently, by delineating water saturation limit in an analytical nephogram, the producing area of fracture-controlled unit can be determined and calculated. The key contributions to producing areas and gas-water productivities at early, middle and late stages are dynamically identified via a sensitivity analysis, thus demonstrating that both fracture length and initial matrix water saturation are key factors contributing to the producing area and productivity. Meanwhile, the producing area shows a positive relation with matrix permeability, cluster spacing and fracture length whereas has a negative relation with initial matrix water saturation. Furthermore, their relationship between producing area and productivity is formulized to show an approximately linear characteristic. Thus, based on field productivities at different production times, their producing areas of fracture-controlled unit can be estimated to evaluate the potential of remaining reserves. This innovative approach with low requirements on the gas-water production dataset is convenient to yield a rapid prediction of dynamic reserves of gas reservoirs, thereby contributing to high-efficient development of unconventional gas resources.