Study On Rational Distribution And Stable Yield Of Fracturing Wells In Tight Gas Reservoirs

In recent years, tight gas, a major source of national natural gas production, which accounts for a larger proportion of natural gas proved reserves, has drawn more attentions in areas of exploration and development at home and aboard. However, compared with conventional reserviors, tight gas reservoirs are generally characterized by worse properties and lower natural productivites, demanding stimulating measures, such as hydraulic fracturing, to enhance their productions. Moreover, both the quality of operation system and the length of stable production period can determine the pratical production effects to some extent. Therefore, studies on rational proration and rate maintenance capability for fratured wells are of great significance to accurately grasp the production performance and efficient development of tight gas reservoirs.Based on large number of domestic and foreign literature researches, this paper dwelled on researching the percolation mechanism, productivity forecasting method, rational proration and rate maintenance capability. Firstly, through literature researches on tight gas reservoirs, a more comprehensive understanding for their percolation mechanisms, including the slippage phenomenon, different stress sensitivity effects in matrix and fracture and the existence of high-speed non-Darcy effects near wellbore have been acquired. On the basis of those mechanisms, the productivity models for fractured vertical well and fractured horizontal well were established respectively by introducing pseudopressure and Lame coefficient of the elliptical coordinates, using superposition principle of potency as well as the theories of conformal transformation and equivalent wellbore diameter. Through an example, the productivity models were validated and production influencing factors were analyzed. Secondly, based on the analysis of principle of empirical method, system analysis curve method, gas recovery curve method and liquid carrying calculation method, combined with productivity models and wellbore pressure calculation model, the rational proration for fractured wells have been calculated and selected. Finally, the single well controlled reserves of fractured wells were calculated by means of the flow of material balance method, cumulative production method, wellhead pressure reduction method and pressure drop method. Meanwhile, the rate maintenance capability of fractured wells under different production allocation and final stable wellhead pressure were calculated by the open flow method and material balance equation method.The research of this paper can offer some theoretical guidance and technical support for productivity prediction, rational proration and rate maintenance capability of fractured vertical wells and fractured horizontal wells, which can establish a theoretical foundation for reasonable exploration and development for such gas reservoirs as well as provide valuable references for the development of similar gas reservoirs.