Analysis of Productivity Influencing Factors in the X Oilfield

Pre-drilled horizontal wells in the X Oilfield exhibited significant variations in production capacity after a 2–4 months shut-in period and prior to the installation of the Upper Group block. Although reservoir geological conditions and fluid invasion-induced damage were identified as influencing factors, their relative contributions remained unclear. This study systematically investigated the impact of interlayer development, sandstone drilling encounter rate, water cut, and fluid invasion damage on well productivity through field data analysis, laboratory experiments, and numerical simulations. Results revealed that the low productivity of pre-drilled horizontal wells was primarily controlled by the presence of N1gIII oil-bearing interlayers, combined with low permeability, poor reservoir properties, and elevated water cut in localized regions. Low-productivity wells showed no significant improvement after acidizing and hydraulic fracturing but exhibited notable in-creases in production following sidetrack drilling due to enhanced reservoir connectivity. However, persistent low production occurred in wells with poor reservoir quality or high water cut. Fluid invasion reduced reservoir permeability by 6%–36%, while emulsification of drilling fluids and crude oil increased oil viscosity by 10–30 times, significantly elevating flow resistance in the invasion zone. Numerical simulations using a conceptual reservoir model of a typical well predicted a production capacity of 28.3 m3/d under combined interlayer and emulsion damage conditions, closely matching the actual production of 28 m3/d. Interlayer development reduced horizontal well productivity by 65.7%, whereas emulsion damage accounted for an 8.4% reduction, demonstrating that reservoir heterogeneity, particularly interlayer distribution, dominated productivity variations, with shut-in-induced damage playing a secondary role. Based on these findings, we recommend: Real-time optimization of well trajectories during pre-drilling based on encountered formation heterogeneity. Mitigation of wellbore storage effects by ensuring post-drilling fluid recovery volumes exceed 1.5 times the wellbore volume to align production capacity with true reservoir potential.