Application of the Hall Plot Method for Monitoring Water Injection Performance and Identifying Thief Zones in Oil Reservoirs

Effective waterflooding is a key method in secondary oil recovery; however, its performance is often reduced by high-permeability thief zones that channel injected water and lower sweep efficiency. This study aims to quantitatively evaluate the Hall plot as a diagnostic tool for detecting such anomalies and assessing their effect on waterflood performance. A comparative numerical simulation was conducted using two reservoir models: a homogeneous reservoir (Reservoir A) and a heterogeneous reservoir containing a thief zone (Reservoir B). Operational data were simulated over ۷۲۰ days to compare production behavior and construct Hall plots. The results showed that Reservoir B required about ۶۱% more cumulative water injection (~۷۱۰,۰۰۰ STB) than Reservoir A (~۴۴۰,۰۰۰ STB) to maintain reservoir pressure, which resulted in earlier water breakthrough and a field water cut rising to ۰.۹۶. Despite the significantly higher injected water volume, both reservoirs produced nearly the same cumulative oil recovery (~۱۲۲,۰۰۰ STB), indicating severe water cycling without additional oil benefit in the thief-zone case. Furthermore, the Hall plot slopes successfully captured the higher injectivity of Reservoir B and enabled estimation of its effective permeability (۸۹.۸ mD), which closely matched the weighted average permeability of the static model (۸۶.۰ mD) with only ۴.۴% deviation. These findings confirm that the Hall plot is a practical and low-cost tool for identifying suboptimal injection behavior, quantifying waterflood inefficiency, and supporting conformance control decisions for improved reservoir management

کلیدواژه ها:

HALL Plot ، Water Injection Monitoring ، Waterflooding