低渗透油藏压力场变化对岩体力学性质的影响

Impact on Mechanical Properties of Rock Mass with Pressure Field's Change in Low-Permeability Reservoirs

以鄂尔多斯盆地安塞油田长6油层为例,在恢复地下围压、油水两相饱和流体、温度等条件下,开展岩芯孔隙压力变化过程中杨氏模量、泊松比、比奥特系数、脆性指数等岩体力学参数的测定。结果显示,随着孔隙压力逐渐增加,杨氏模量、比奥特系数和脆性指数逐渐减小,泊松比逐渐增大,并且相对变化幅度较大,分别为13.15%,37.50%,68.65%和52.22%。这一结果表明,在低渗透油藏开发过程中,随着油水井之间压差增加以及整个油藏压力场不均衡分布,岩体力学性质及应力场与原始未动用油藏相比发生了较大变化。在老井重复压裂改造和水井配注中应充分考虑这种变化,以达到提高低渗透油藏采收率的目的。

Ansai Oilfield Chang-6 Reservoir in the Ordos Basin is chosen as an example. The conditions were restored to actual confining pressure, oil and water two phase saturated fluid, temperature and other. Determination of the rock mechanics parameter were performed. The results show that Young＇s modulus, Biot＇s coefficient and brittleness index decrease, Poisson＇s ratio increases with the increase of the pore pressure. The relative range of change is 13.15%, 37.50%, 68.65% and 52.22% respectively. In the development process of low-permeability reservoir, great changes would happen in mechanical properties and stress field. IN order to enhance the recovery, this kind of change should be fully considered in repeated fracturing modification, fracturing and injection allocation.