低渗透气藏地层压力监测技术

LOW-PERMEABILITY GAS RESERVOIR PRESSURE MONITORING TECHNOLOGY

“压力是气田开发的灵魂”,而如何准确获取气田的目前地层压力,是靖边气田开发的主要难题之一。一方面,由于靖边气田储层具有低渗透、低丰度、大面积、薄储层、非均质性强,开发井距大(一般大于2.5km)的特征,气井关井后压力恢复时间很长,压力恢复稳定往往需要几个月以上的时间;另一方面,近年来,气田日产气量居高不下,很难有区块关井等测压时机,这些均给气田目前地层压力的求取带来了困难。对这类低渗透气藏而言,在确保生产任务的前提下,采用尽可能少的监测工作量,满足开发研究的需要,这是气藏开发工作必须解决的问题。针对靖边气田的地质特征,通过多年的不断研究和总结,逐渐形成了以建立观察井网、设立定点测压井、结合少量压恢试井和区块整体关井测压等配套技术,以获取气藏的目前地层压力。

Pressure is the essential factor to consider in gas field development. One of the key difficulties encountered in Jingbian Gasfield Development is how to obtain the accurate current formation pressure. On the one hand, since Jingbian Gasfield features low permeability, low abundance, large in area, thin reservoir, obvious heterogeneity and large production well interval (generally>2.5 km), it takes as long as several months to reach stability after pressure build-up upon re-startup. On the other hand, Jingbian Gasfield has been experiencing high daily gas yield in recent years and the chances to shut down well and measure pressure is rare. These factors attributed to the difficulty to measure current formation pressure. It presents a problem that has to be solved in developing low permeability gas reservoirs like Jingbian Gasfield, that is, how to achieve production target while still sustaining reservoir study with minimum monitoring activities. In line with geological characteristics of Jingbian Gasfield, based on continuous research and accumulation, the comprehensive technology has gradually been developed to measure current formation pressure, including building monitoring well network, setting up dedicated pressure monitoring well, well testing for pressure build-up on small scale and whole block shutdown for pressure measurement.