Inversion method for effective drainage volume of tight oil horizontal wells with volume fracturing based on production analysis

This study aims to accurately determine the effective drainage volume (EDV) in tight oil reservoirs, which is critical for optimizing development strategies and fracture treatment designs in China’s tight oil reservoirs. The work addresses the key challenge that a significant portion of the stimulated reservoir volume (SRV) does not contribute to production, necessitating reliable methods to evaluate the actual productive volume. A rate transient analysis (RTA) model for horizontal wells with volume fracturing was developed based on material balance principles, incorporating stress sensitivity and coupled oil-water flow mechanisms within the effective stimulated reservoir volume (ESRV). The study established a flow-material balance coupling equation for the ESRV, typical type curves for volume fracturing RTA, and an analytical method for ESRV calculation. The model was applied to assess ESRV in two case wells (M2-1 and P2-1) using production data. Analysis results revealed that the ESRV constitutes only 40–60% of the total micro-seismic interpreted SRV, the developed RTA model provides an efficient and accurate method for EDV quantification, and the type curves and analytical approach effectively characterize the productive fracture network. This research presents the first integrated RTA model incorporating stress sensitivity and multi-phase flow for tight oil EDV evaluation, a practical methodology to distinguish productive ESRV from total SRV using production data, and quantitative evidence of the significant discrepancy between SRV and actual drainage volume. The findings provide crucial guidance for optimizing fracture treatments and development strategies in China’s challenging tight oil reservoirs.