Diagnosis of Atypical Water Injection Mechanisms for Production System Integrity Management: A Case Study of X Field

Abstract

In the absence of a reservoir pressure maintenance (RPM) system at Field X, a critical increase in water cut to 92.6% has been observed, with current production at 72.4% of the initial recoverable oil reserves. Such a high water cut at a stage that does not correspond to full production suggests the presence of atypical mechanisms. This study aimed to comprehensively analyze the causes of the abnormal water cut using modern diagnostic methods, including geophysical well logging (GWL), reservoir pressure monitoring, hydrogeochemical analysis of associated waters and detailed laboratory studies of core samples. The analysis revealed that the primary cause is a man-made breach in the production column of Well #4, resulting in the overflow of highly mineralized water from the overlying Albian-Cenomanian aquifer into the productive J-XI formation. Petrophysical studies revealed high reservoir heterogeneity. However, the oil displacement coefficient by water was 0.53 for highly permeable formations, ruling out low oil recovery as the main cause of water flooding. Key evidence of the human-made nature of the problem includes the abnormal increase in reservoir pressure, from 23.9 MPa in 2022 to 25.5 MPa in 2023, as well as the presence of sulphate ions in the production water, which is characteristic of the Albian-Cenomanian complex. A set of practical recommendations has been developed, including the urgent repair and insulation of Well #4, the introduction of a casing integrity monitoring system and the adaptation of the development strategy. The results emphasize the importance of monitoring the technical condition of the well fleet to ensure the effective late-stage development of similar fields. The study demonstrates that integrating this diagnostic methodology into a production management system enables proactive risk mitigation, supports decision-making for well intervention, and contributes to optimizing the overall production strategy in mature fields.