Formation pressure calculation of tight sandstone gas reservoir based on material balance inversion method

Pressure is the soul of a gas reservoir. Formation pressure is the basis of evaluating gas well productivity and analyzing gas reservoir potential. However, due to data integrity and method applicability limitations, formation pressure in most gas wells cannot be accurately obtained. On the basis of a small amount of pressure monitoring data, the material balance inversion method is proposed by using mathematical inversion thought to evaluate the formation pressure of tight sandstone gas reservoirs. Firstly, the dynamic reserves of gas wells are calculated by fitting the Blasingame chart with the production data of gas wells under pseudo-steady flow. Secondly, the material balance equation is established through the inversion of dynamic reserves and one pressure monitoring datum, and the cumulative gas production is substituted to evaluate the formation pressure. Finally, the calculation of formation pressure of tight sandstone gas wells in Daning-Jixian Block shows that: (1) The material balance inversion method requires only one pressure measurement point to evaluate the formation pressure variation of gas wells; (2) The initial formation pressures of gas wells vary greatly, and the formation pressure changes of single wells are complex with multiple pressure systems. (3) The inconsistency of the pressure system is related to the strong heterogeneity of the reservoir. The research results provide a reliable method for single well pressure calculation and tight gas reservoir pressure evaluation, and lay a foundation for tight gas reservoir development plan adjustment and benefit development. © 2022 COAL GEOLOGY & EXPLORATION. All rights reserved.