长庆气区低渗透非均质气藏可动储量评价技术

气藏可动储量是指在现有工艺技术和现有井网开采方式不变的条件下,已开发地质储量中投入生产直至天然气产量和波及范围内的地层压力降为零时,可以从气藏中流出的天然气总量。开展气藏可动储量评价,落实开发基础,是气田后期开发调整的重要依据。长庆气区储层渗透率低、非均质性强,加之气井排水采气、冬季用气高峰期提产等因素,导致利用常规方法评价气井可动储量存在地层压力测试点少、气井工作制度不稳定等难点。针对上述问题,充分应用气藏生产动态资料,通过重整压力和流量将气井变压力、变流量生产数据转换为等效恒压力或恒流量数据等途径,在常规压降法评价的基础上,形成了产量不稳定分析法、流动物质平衡法、优化拟合法等气井可动储量评价方法。应用上述方法全面追踪评价了长庆气区靖边、榆林等气田单井可动储量及其变化,为气田加密井部署、工作制度优化、储层二次改造井优选等提供了依据,进一步提高了气田储量动用程度。

Evaluation techniques of dynamic reserves:Case history of low-permeability and heterogeneous reservoirs in Changqing gas fields

Dynamic reserves refers to the gross of the natural gas gained from the reserves when the developed geological reserves have been put on stream until the yields of the natural gas and the formation pressure of related areas decrease to zero, under the conditions of constant process engineering and constant way of exploit on the current gas wells. Carrying out evaluations on dynamic reserves and foundations for the development is an important basis for the adjustment of late development on the gas fields. The gas fields in Changqing are characterized by low permeability and strong heterogeneity, together with the factors of drainage gas recovery, production boosting in the high gas consumption period in winter, resulting in the difficulties like lack of the pressure testing data and frequent change of the working system when the dynamic reserves are evaluated by regular methods. To solve these problems, based on the P/Z method and the full use of performance data, we have tried the approaches of reconstructing pressure and flow to change the production data of variable pressure or production rate into equivalent constant pressure or production rate, and have developed the RTA (Rate Transient Analysis) method, FMB (Flow Material Balance) method and optimizing method. Furthermore, all these methods have been applied to trace dynamic reserves of the gas wells in the Jingbian and Yulin gas fields in Changqing. This has offered a significant basis for well infilling, optimizing of working systems, selecting of secondary stimulation wells, and improved the percentage of producing reserves.