Understanding reservoir pressure dynamics and crosswell interference is crucial for optimizing pressure maintenance systems in heterogeneous reservoirs with complex geology. This paper presents a case study from Eastern Siberia, highlighting the positive impact of applying Multi-Well Retrospective Test (MRT) machine learning technology on production enhancement.
MRT technology relies on mathematical algorithms for annualizing long-term records of bottomhole pressure and surface rates from a group of wells through multiwell deconvolution. It requires historical data of bottomhole pressures for the tested well and flow rate history for all wells under study. Multiwell deconvolution involves a fully or semi-automated search for initial pressure and Unit-rate Transient Response (UTR) for tested wells and cross-well intervals, aligning actual pressure records with total sandface flow rate variation history. It also quantifies the accumulated pressure impact of surrounding wells on the tested well.
The study area featured nine wells with declining production rates, including six producers and three injectors. The primary objective was to assess production enhancement potential, primarily through injection optimization. The seven-year dataset encompassed flow rate and pressure variations during production. Before employing machine learning, data were preprocessed to reduce the number of analysis points, synchronize flow rate and pressure change timings, and remove outliers. Mathematical deconvolution procedures were then applied to derive UTRs, with UTR convolution providing crosswell pressure impact. Two injection wells were found to have a significant cumulative pressure impact on production wells. Mathematical well shut-ins yielded reservoir pressure and well productivity index. UTR interpretation via pressure transient analysis algorithms offered insights into reservoir transmissibility, well skin, and interference-free drainage areas. Machine learning algorithms generated pressure/rate forecasts for different well targets, indicating that the optimal production increase could be achieved through a 1.5x increase in injection rate for one well and a 2.7x increase for another well, resulting in a twofold oil production increase with constant water cut.
Field implementation demonstrated that MRT technology is a powerful tool for optimizing injection targets and increasing oil production. Additionally, MRT provides reservoir pressure data without well shut-ins, enabling the operator company to gather information for reservoir pressure mapping without production deferment, resulting in a significant increase in Net Present Value (NPV).