提升水驱气藏开发效果的先期控水技术

活跃水驱气藏通常会因为水侵、水淹而造成开发效益降低,使得该类气藏的采收率远低于不活跃水驱气藏。为此,提出了先期控水的技术思路。其原理是对活跃水驱气藏在开发早期就采取控水措施,即在水驱气藏投入开发前,认清水体分布特征,预测水侵方向、方位及水侵量,在地层水侵入的源头利用控水井先期开展控水作业,尽量延缓气藏水淹的时间。具体方法是:在气藏发生水侵的高渗条带的来水方位上部署控水井,实施排采泄压、阻隔拦截、诱导转向,或利用水驱气藏下部的低压储层对气藏侵入水实施纵向灌注、邻层转储,以削弱侵入水的能量、改变侵入水的流向、抑制边底水的活跃性,达到减缓水侵速度、阻隔水侵路线、减少水侵面积的目的,进而提升水驱气藏的开发效果、提高水驱气藏的最终采收率。以柴达木盆地涩北气田为例,进行了先期控水技术的部署与尝试。结论认为:该项技术是与油田注水开发相似但又相反的,可实现水侵气藏均衡开采、控水稳气的保护性开发技术。

Early-stage water control technology in improving the development effeciency of water drive gas reservoirs

An active water drive gas reservoir often suffers from water invasion and water flooding, making its development benefit low with its recovery factor far less than that of an inactive water drive gas reservoir. In this paper, the technology of early-stage water control was proposed, namely, water control measures are taken in the early development stage of active water drive gas reservoirs. Before a water drive gas reservoir is put into development, it is necessary to figure out the distribution characteristics of water body, predict the direction, azimuth and volume of water invasion and carry out water control from the source of formation water invasion by using water control wells, so as to delay the water flooding of the gas reservoir. Specifically, water control wells are deployed at water source locations of a high permeability zone where the gas reservoir suffers from water invasion to conduct drainage for pressure relief, cutoff and interception and induced diversion. Otherwise, the low pressure reservoir below the gas drive gas reservoir is used for vertical flowing of water invading the gas reservoir or transformed into water reservoir to diminish the energy of invasion water, divert the flowing direction of invasion water and inhibit the activity of edge and bottom water. Thus, the water invasion velocity is slowed down, the water invasion pathway is cut off and the water invasion area is reduced. As a result, the development effect of the water drive gas reservoir is improved and its ultimate recovery factor is enhanced. Taking the Sebei Gasfield in the Qaidam Basin as an example, we made the field application of the early-stage water control technology and also evaluated its implementation effect. It is concluded that this technology is a protective development technology which is similar to but opposite to water flooding development of oil fields. By virtue of this technology, balanced production, water control and gas stabilization of watered-out gas reservoirs is realized.