阻流带对子洲气田低渗透砂岩气藏开发的影响

Impact of blocking zones on the development of low-permeability sandstone gas reservoirs in the Zizhou Gas Field,Ordos Basin

低渗透砂岩气藏的储层物性差、非均质性强,阻流带发育,从而造成气井的控制储量低,因而在分析气田整体开发指标时需要对阻流带进行评价。为此,以鄂尔多斯盆地子洲气田为例,综合地质分析、试井解释和数值模拟等方法对低渗透砂岩气藏中的阻流带进行了研究。通过地质资料分析揭示了阻流带主要存在的两种模式,即河道的底部滞留沉积和河道边部沉积引起的致密夹层。结合试井解释和气井的生产动态历史拟合,可得知该地区的阻流带间距大小不等,差别较大,间距一般在200～2 000m。区块整体开发的数值模拟结果表明,子洲气田的单井控制面积约为1.3km2。结论认为,阻流带的间距、形状对气田的储量动用程度和采收率影响不大,当阻流带隔离开的流动单元的面积为1.2km2、井网为1 200×1 200m时,气田的储量动用程度可达60%,采收率在47%左右。阻流带的研究为评价气井的产能和气田的整体开发指标提供了必要的参数。

Low-permeability sandstone gas reservoirs have strong heterogeneity and developed blocking zones, which affect the con- trolled reserves of gas wells. Therefore, we will assess the blocking zone when analyzing the overall development indexes of a gas field. Taking the Zizhou Gas Field, Ordos Basin, for example, we conducted a study on the blocking zone of the low-permeability sandstone gas reservoir using such methods as geological analysis, well test interpretation and numerical simulation. Through analy zing the geological data, we discovered two existing modes of blocking zones, respectively the lag deposits at the bottom of a river and the tight interlayers formed by the deposits along the sides of the river course. According to well test interpretation and the his- torical data fitting of well production performance, the blocking zones in this area are unevenly distributed~ the distances among them vary greatly from 200 to 2000 m. The numerical simulation for the overall development in this block indicates that the controlled area by a single well in the Zizhou Gas Field is about 1.3 km^2. Upon a comprehensive study, it is concluded that the spacing and shapes of blocking zones have little impact on the producing degree and the recovery efficiency of the gas reservoirs in this field. The produ- cing degree will reach 60M and the recovery efficiency about 47% there if the isolated flow unit area of the blocking zone is 1.2 km2 and the well pattern is laid out as 1200X 1200 m. This study provides necessary parameters for assessing the production capacity of a gas well and the overall development indexes of a gas field.