压敏油藏的压力动态摄动分析

PERTURBATION ANALYSIS OF PRESSURE TRANSIENT RESPONSE IN STRESS-SENSITIVE RESERVOIRS

在对压敏油藏的压力瞬态分析时,假设各种岩性为常数,用以确定压敏油藏的传输性与储容性会造成非常显著的误差;另一方面,与压力有关的各种岩性使得在油藏中描述压力的控制方程是非线性的,这些非线性性只能利用数值方法进行近似处理,如果渗透率模量是确定的,这些非线性可以弱化。假设渗透率模量为常数,通过引入Pedrosa变换,使得压力控制方程的非线性弱化,并利用正规摄动法获得在无穷大边界条件下的一阶摄动解;同时,借助半解析的数值计算方法,将井底压力动态行为图形化,使之易于直观分析。

The assumption of constant rock properties in pressure-transient analysis of stress-sensitive reservoirs causes significant error in determination of reservoir transmissibility and storage ability. On the other hand, inclusion of pressure-dependent rock properties makes the governing equation for the pressure in the reservoir nonlinear These nonlinearities can be treated only approximately by numerical means. If a permeability modulus is definite, the nonlinearities associated with the governing equation become weaker. With the permeability modulus assumed to be constant and Pedrosa transformation introduced, the nonlinearity of the governing equation for the pressure becomes weaker and the first-order perturbation solution is obtained for a radial reservoir with infinite boundary condition by use of the regular perturbation method. Simultaneously, for the facility of analysis, the pressure-transient response is shown diagrammatically by use of semi-analytic and semi-numerical methods.