基于物质平衡反演法的致密砂岩气藏地层压力计算

压力是气藏的“灵魂”，地层压力是评价气井产能，分析气藏潜力的基础。然而，受到资料完整程度、方法适用条件等因素的限制，大部分气井无法准确获取地层压力。为了评价致密砂岩气藏地层压力，基于少量压力监测资料，采用数学反演思维，提出物质平衡反演法。首先，利用拟稳定流动状态下气井生产数据，拟合Blasingame图版，计算气井动态储量。而后，通过动态储量及一个测压数据进行反演，建立物质平衡方程，代入累产气量，评价地层压力，最后，以大宁–吉县区块致密砂岩气井为例，进行地层压力计算。结果表明:(1) 物质平衡反演法仅需一个测压点，可以评价气井的地层压力变化。(2) 气井原始地层压力差异大，单井地层压力变化复杂，存在多个压力系统。(3) 压力系统不一致与储层非均质性强有关。研究结果对于致密气单井压力计算和致密气藏压力评价提供了可靠的方法，为致密气藏开发方案调整和效益开发奠定了基础。 

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.