Abstract:
Objective Addressing the issue of inaccurate productivity evaluation in deep carbonate gas reservoirs caused by multi-mechanism coupling including stress sensitivity, water invasion, and blockage effects, a multi-factor collaborative quantitative productivity evaluation method is established using the Penglai gas field Dengying Ⅱ Formation in the Sichuan Basin as the research object.
Method Based on the dual-medium flow theory framework, the Forchheimer non-Darcy correction was introduced to describe high-velocity flow inertial effects, combined with stress-sensitive constitutive relations to quantify dynamic permeability decline, characterized water invasion evolution processes through staged water saturation models, and reflected near-wellbore blockage degree using skin factors to construct a gas-water two-phase multi-factor coupling productivity model. A quasi-steady-state semi-analytical method was employed for solution, with key parameters constrained through well testing and production data.
Result The results indicated that the relative error of absolute open flow prediction ranged from 1.2% to 4.3%, with errors below 3.5% during water invasion stages. Quantitative analysis revealed that blockage effects caused productivity losses up to 36%, stress sensitivity induced productivity decline of 30%-45%, while water invasion has relatively minor impact (2.0%-4.6%). Field applications confirmed that controlled pressure production could reduce monthly decline rates from 3.2% to 1.8%, and acidization treatments achieve 93% productivity recovery.
Conclusion This productivity evaluation method accurately assesses gas well productivity and influencing factors in deep carbonate gas reservoirs, providing technical support for formulating differentiated gas well productivity maintenance measures and offering and important guidance for enhancing development benefits of similar gas reservoirs.
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