电缆地层测试复合流动压力转换模型

大排量电缆地层测试器在较薄储层测试时,压力波动很快传到储层上下边界,流动形态由球形流动过渡到平面径向流动,可以借鉴常规试井或钻柱地层测试(DST)产能评价理论进行产能评价,但其不同于DST测试。DST测试的井底流压为储层厚度上的平面径向流压力,而电缆地层测试获得的探头处压力为球形流压力。因此,如果想利用常规试井方法获得储层产能,就必须将探头的压力转换成等效的平面径向流压力。针对该问题,利用渗流力学方法推导了球形流-径向流压力转换模型,可将电缆地层测试探头处的球形流压力转换成等效的径向流井底流压,进而通过不同稳定测试流量下的压差-流量数据进行产能评价,为大排量电缆地层测试实现产能评价提供了必要的理论基础,从而拓展了电缆地层测试的功能。

Composite flow pressure transformation model of wireline formation test

When the wireline formation tester with high duty pump is used for testing in thin reservoir, pressure quickly propagates to the upper boundary and lower boundary of reservoir. Flow pattern is from spherical flow to radical fluid flow. Deliverability evaluation can be executed by the deliverability evaluation theory of conventional well testing or DST. But it is different form DST test. Bottom hole flowing pressure with DST test is radial fluid flow for reservoir thickness, and the probe pressure acquired by wireline formationtest is the spherical flow pressure. Therefore, probe pressure must be transformed into equivalent radial fluid flow pressure if we want to obtain the reservoir deliverability through conventional testing method. In view of this problem, this paper derives the pressure transformation model from spherical flow to radical flow by fluid mechanics in porous medium. The spherical flow pressure at the probe of wireline formation tester can be transformed into the equivalent bottom hole flowing pressure of radical flow. Deliverability evaluation can be conducted through the pressure difference-flow rate data with different stable tests, which provide the theoretical base for the deliverability evaluation by wireline formation test with high duty pump, and extend the function of wireline formation test.