Multi-Lateral Horizontal Well Optimization in Offshore Tight Gas Reservoirs with Novel Numerical Simulation Methods

Abstract Tight reservoir shows significant potentials in offshore China. Yet unlike onshore situations, multistage completion and hydraulic fracturing are not a regular practice in offshore due to the economic and safety reasons, while multi-lateral horizontal wells are considered promising in the development of such reservoir type. In this work, we support the well planning with several noval numerical simulation methods, including stress-sensitive permeability settings, ensemble-based workflow, downhole integrated production analysis, and tracer tracker techniques. With the support from reservoir simulation, we achieved outstanding results from the operations and productions. Y-Field is a tight gas reservoir from offshore China discovered in late 2000s. Though potential is high, it proves to be very difficult for the development, as the previous trials in the vertical well or the horizontal well with multistage fracturing completion proved to be uneconomical and risky due to water production. In 2023, the development strategy was switched to multi-lateral horizontal wells, while numerical simulation technologies need a breakthrough to optimize the lateral position, direction, length, well pattern, etc. The noval simulation methods we used in this work were: 1) using stress-sensitive setting to represent non-linear flow behavior in the tight formation; 2) using ensemble-based workflow for lateral trajectory optimization; 3) using downhole integrated production analysis to identify the behavior and contribution from each lateral; 4) using tracer tracker techniques to study the drainage dynamics in the field. The combination of those noval simulation practice enables the proper well planning in the sweet spots, increasing the drilling net to gross ratio, and improving the production performance in this field. With the technical support from this work, four horizontal wells are drilled in the Y Field, two of which is multi-lateral horizontal wells. All the horizontal wells drilled in the field perform well. The simulation method used in this work, as well as the multi-lateral horizontal well completion method, provides a promising alternative in the offshore tight gas reservoirs.