克拉玛依油田七区八道湾组砂砾岩油藏地应力特征

克拉玛依油田七区八道湾组油藏储集层以中—粗砂岩和砾岩为主,油藏开发时间长,剩余油分布广,为实现小层挖潜,弱化储集层非均质性,实施了精细分层压裂。在储集层改造过程中,出现了裂缝穿过隔夹层沟通水层的情况,挖潜效果较差。为了明确储集层的岩石力学特性和区域地应力分布状态,采用室内岩心实验和现场资料分析相结合的方式,建立油藏三维应力场模型。研究发现,油藏西南部和中部应力差异不大,油藏东南部应力受断层影响较大,西南部应力受断层影响较小;研究区内发育5条逆断层且地层倾角变化较大,并在断层的交会处产生应力突变,对后期的压裂施工有较大影响,因此需要调整施工参数;在油藏西南部和中部裂缝向上向下延伸均匀,在油藏东南部深部地区,若隔夹层较厚,裂缝则向较为容易延伸的方向大幅延伸,易沟通水层,隔夹层较薄时,裂缝易穿透上下夹层。对2 m3/min和3 m3/min排量下的裂缝高度进行了模拟,发现在3 m3/min排量下裂缝的高度控制困难,裂缝纵向延伸较大,沟通下部底水;在2 m3/min排量下,裂缝延伸控制容易,纵向延伸合理。

Characteristics of In-Situ Stress in Sandy Conglomerate Reservoir of Badaowan Formation in District No.7, Karamay Oilfield

The reservoir of Badaowan formation in District No.7 of Karamay oilfield is dominated by medium-coarse sandstone and conglomerate. The reservoir has been developed for a long time and remaining oil is widely distributed in the formation. In order to realize potential tapping in small layers and to reduce reservoir heterogeneity, separate-layer fracturing has been carried out. In the process of reservoir stimulation, some fractures penetrated interlayers and connected with water layer, resulting in poor stimulation effect. In order to understand rock mechanical characteristics and regional in-situ stress distribution, the paper establishes a 3D stress field model for the reservoir on the basis of lab core experiments and field data analysis. The stresses are almost the same in the southwestern and central part of the reservoir, the stress in the southeastern part is greatly influenced by fault and that in the southwestern part is influenced by fault gently. 5 reverse faults with large dip angle variations are developed in the study area and the stress mutation occurs at the junction of the faults, which will impact fracturing operation, therefore the operation parameters should be adjusted. The fractures in the southwestern and central reservoir extend upwards and downwards evenly. In the southeastern part of the reservoir, fractures tend to extend along the directions easily to stretch if encountering thick interlayers, so that the aquifer is connected, and fractures can easily penetrate thin interlayers. The fracture heights under the displacement of 2 m ³/min and 3 m ³/min are simulated and it is found that the fracture height under the displacement of 3 m ³/min is hard to be controlled due to the fracture’s large vertical extension and its connection with bottom water, and the fracture extension under the the displacement of 2 m ³/min can be controlled.