川东石炭系气藏合理开发井网分析及探讨

DISCUSSION ON REASONABLE DEVELOPMENT WELL PATTERN FOR CARBONIFEROUS GAS RESERVOIRS IN EAST SICHUAN

在川东地区的石炭系气藏,以福成寨、张家场等为代表的老气田开发效果较好,各生产井配产合理,全气藏始终维持均衡开采,未明显引发边水的快速推进,动态储量逐步增大,气井稳产时间延长,开采效益很好;而以云和寨、双家坝等为代表的新气田,因生产井网较稀、井距较大,气井控制全气藏的难度较大,而单井配产又高,气井在投产2～5a后就易引发严重的压降漏斗,导致气井提前产水,并使部分含气区的储量被水淹或分割而无法动用,气藏稳产期缩短,难以达到开发预测水平,开发效益变差。文章通过总结川东地区石炭系气藏20多年的开发经验,对气田的地质模式、井网分布、气井生产过程的综合对比,认为合理的生产井网密度对中—低渗非均质性气藏是非常重要的,是确保气藏开发指标如期实现、提高气藏最终采收率和整体开发效益的关键因素。中—低渗非均质性气藏的合理井网密度为3.0km2/口左右,单井控制的储量(5.0～10.0)×108m3,采气速度控制在3.0%～4.0%。

In Carboniferous gas reservoirs of East Sichuan, the old gas fields, such as Fuchengzhai, Zhangjiachang etc., have good development results. All the production wells have suitable allocation. Balance exploitation is always maintained for the whole gas reservoir. No rapid invasion of edge water happens obviously. The dynamic reserves increase gradually. The stable production period of gas wells is prolonged and the recovery benefit is good. But for new gas fields, such as Yunhezhai, Shuangjiaba etc., it is difficult for the gas wells to control the whole gas reservoir because the sparse well pattern and big well space. The severe pressure drop funnel is formed in 2 - 5 years after the gas wells are put into production and the ahead water production happens because of the high allocation for each well. Therefore, the reserves of some gas-bearing zones can't be used because they are watered out or separated by water. The stable production period of gas reservoirs is shortened. It is hard to reach the expected development level. The development benefit becomes poor. With summing up the development experience of more than 20 years for Carboniferous gas reservoirs in East Sichuan and comprehensively comparing the geological mode and well pattern of gas fields and the production process of gas wells, it is found the reasonable density of well pattern is very important for the non-homogenous gas reservoirs with low-medium permeability, and is the key factor to guarantee realization of the development indexes of gas reservoirs in time and improve the ultimate recovery factor and whole development benefit of gas reservoirs, The reasonable density of well pattern should be about 3.0 km2/well, the reserve controlled by a well should be (0. 5 - 1, 0) × 109 m3, and the gas recovery rate should be 3. 0% - 4. 0% for the non-homogenous gas reservoirs with low-medium permeability.